1 (Evolution): since 1914 began the commercialization of self tapping screw design. First is mainly from wood screws - can carburizing steel tail cone type A. The purpose of the main thread forming screws was used in air conditioning system of tin catheter joint, also known as iron screws. After 80 years of development. Can be divided into four periods: thread forming, thread cutting, thread rolling and self drilling.
Thread forming screws (Thread Forming Tapping Screws) - Department of iron screw directly by the development of, must be pre drilled thread forming screws when using the screw hole, strong extrusion with female thread, while the original material in the female position will be pushed to the male, this is called self tapping screw thread forming. Only applicable to thin and malleable materials, and thus develop; thread cutting tapping screws (Thread Cutting Tapping Screws) - cut out one or more of the cutting thread end is screwed into the mouth, enabling in pre drilling, using screws and dental screws similar to the tail the way of cutting out with female thread. It can be used in thick, hard or brittle materials, is not easy to shape.
Thread rolling screws (Thread Rolling Tapping Screws) - triangular tapping screws, also known as Type (TT Type Tai still has the patent department) principle is based on the forming of screw, self tapping screws with screw thread rolling and end special design in the screw pressure to roll off with the female thread. At the same time in the material around the hole can easily fill the space and the bottom of the self tapping screw thread, because the friction force is thread forming self tapping screw is small, so it can be used in material thickness, rotating torque required for better control, and the combination of higher strength after the thread. Rolling tapping screws the engineering standard definition of forming or cutting tapping screws in the material, heat treatment, definition of strength is higher and more clear, the thread rolling screws become the real "structural" button.
Self drilling screws (Self Drilling Tapping Screws) - also known as Tec, in the process of assembling all self tapping screws, the cost is the pre drilling preparation. Using self tapping screws, must be drilled. And aperture must also limit. Without pre drilling and in some ways can save the cost of this is. In drilling, tapping, tapping screws tightened in one operation. The surface hardness and hardness in the center drilling screws a little higher than the general self tapping screws, this is because the drilling screws has a drilling operation, also need to be drilling screw penetration test, to test the screw drill within the specified time and attack. The thread for the design and development process of four kinds of self tapping screws, and two kinds of special screw thread design, the first one is low; tapping screws (High - Low Tapping - Screws) for use in plastic or other Low-density material. Double thread design, high thread (tooth outer diameter) is more flat more sharp angle for 30 degrees of thread thread type. (thread tooth thread has a smaller diameter) 60 degrees angle, tooth high only half as high as threads. Thread level combination design reduces the torque, improve the pull-out strength, significantly decreased the risk of rupture of a combination of work in the construction industry on the dry wall (Drywall) assembly purposes. Such design, with self tapping thread screw is particularly suitable for plastic parts, plate and wood.
The other one is double thread; self drilling point tapping screws (Twin Lead Self Drilling Point Tapping Screws) - assembly can be easily screwed into the dry wall, in the iron and steel self drilling a hole on the teeth and tapping with the female thread. The bear head with concave horn surface can be screwed in, not in as for the damage to the wallpaper or plaster surface. Most of the self tapping screws are for commercial purposes, such as when the screws in combination screw (SEMS) to provide, can provide services more closely. And as having special screw thread thickness with designers in assembly after locking.
2 engineering standards: self tapping screw size, mechanical, functional performance of the following criteria:
ANSI/ASME B18.6.4─Thread Forming And Thread Cutting Tapping Screws And Metallic Drive Screws (Inch Series)
SAE J933─Mechanical and Quality Requirements For Tapping Screws
SAE J81─Thread Rolling Screws
SAE J1237─Metric Thread Rolling Screws
SAE J78─Steel Self-Drilling Tapping Screws
FIP 1000─Tapping Screws Performance Specifications
DIN 7500─Thread Rolling Screws For ISO Metric Screws Thread
DIN 7504─Self-Drilling Tapping Screws Dimensions, Requirements And Testing
ISO 2702─Heat-Treated Steel Tapping Mechanical Properties
JIS B1055─Mechanical Properties For Heat-Treated Steel and Stainless Tapping Screws
Mechanical threads, like British and American Uniform threads, have thread angles of 60 degrees and of the same pitch as coarse and fine threads. If the screws are missing or need to be removed, they can be replaced by standard threaded fasteners
With a 60 degree wide screw thread angle but the pitch is wide, due to its wide pitch so the steeper the screw thread lead than mechanical screw great. Another is specially used for plastic thread, the thread angle is 48 degrees, commonly known as PT screws.
Self tapping screw thread forming A, AB, B, BP, C and other types has been gradually replaced by the self tapping screw thread rolling, it is not recommended to use in the new design. AB, B, BP different only in the shape of a tail, AB has a screw tail cone, B has a blunt tail, BP have a screw cone tail, tail center into pre drilled and began the thread forming. Thread cutting tapping screws are BF, BP, D, F, G and T, BF, BP as wide threads, for the rest of the mechanical screw.
Identification of different character point lies in its tail cutting. Each cutting tail has a shape of cutting waste can be collected. If the self tapping screw into the blind hole (through hole), the residual debris and sealed in the bottom of the hole. But if scored through holes, it will waste away on the other side. The workpiece. So in the choice of the type of self tapping screws must be considered when the waste may cause pollution, or the operation of parts into the electronic board can not operate.
All threads rolled into self tapping screws are mechanical threads, identical to those of United Kingdom and United threads. See SAE J81. See metric SAE, J1237 and DIN7500 for metric threads
Tapping screw thread cutting width BSD and mechanical screw CSD two types. There are other types of special thread, including high-low double thread, and a variety of drilling is also applicable. Because the attack drill tail and thread properties, fermacell screw is not suitable for the blind operation. Self drilling screws during assembly, drill tail completely the rear can penetrate the workpiece or cutting thread forming, so often there will be some debris, if using the thread cutting thread, inevitably there are more debris. Therefore must consider this practical problem. There are about BSD and CSD drilling screws see SAE J78 and DIN7504 (wide thread) regulations.
Self tapping screw thread is the most important part of the tooth diameter, if too large, will cause the assembly torque increase, if the thread is too small, the shear strength will be reduced, and this feature can be easily determined by caliper and micrometer or, in addition to this characteristic, the self tapping screws without any thread measurement, the what is clear, with female screw tapping screw drilling and can cooperate, so without any coordination measurement, though, but still need to pay attention to manufacturing provisions of ANAI/ASME B18.6.4: C.D.F.G and T: its size shall not be less than 2A of the minimum effective thread diameter should not be greater than the maximum tooth so sometimes in diameter. Customer requirements. When required, because the cut ditch limit ring can not be successfully test, must use the thread in the thread indicating gages measurement. Another two self tapping screw thread characteristics is worth mentioning:
The self tapping screw thread forming screw extrusion molding is due to its complex, so that the screw tooth bottom diameter is slightly less than the required pre drilling, in order to have the space to accommodate the workpiece material is extruded out. And the shear strength of the thread will be larger. The thread cutting tapping screws with thread cutting because of its shape, so that the screw tooth bottom diameter is approximately equal to the required pre drilling, and the preset torque is small, breaking strength and pull-out strength is relatively low.
Tapping screw thread diameter and test iron plate bore ratio
Type Hole Size Hole Size/d
A AB F,TT d A AB F TT A AB F TT
#2-32 #2-32 #2-56 0.086 0.076 0.076 0.073 0.075 0.884 0.884 0.849 0.872
#3-28 #3-28 #3-48 0.099 0.081 0.081 0.081 0.087 0.818 0.818 0.818 0.879
#4-24 #4-24 #4-40 0.112 0.086 0.086 0.096 0.098 0.768 0.768 0.857 0.875
#5-20 #5-20 #5-40 0.125 0.107 0.107 0.101 0.110 0.852 0.852 0.808 0.880
#6-18 #6-20 #6-32 0.138 0.116 0.116 0.120 0.120 0.841 0.841 0.870 0.870
#7-16 #7-19 … 0.151 0.129 0.129 … … 0.851 0.851 … …
#8-15 #8-18 #8-32 0.164 0.136 0.136 0.147 0.147 0.829 0.829 0.896 0.896
#9-14 … … 0.177 0.149 … … … 0.842 … … …
#10-12 #10-16 #10-24 0.190 0.159 0.159 0.173 0.166 0.837 0.837 0.911 0.874
… … #10-32 0.190 … … 0.177 0.172 … … 0.932 0.905
#12-11 #12-14 #12-24 0.216 0.188 0.188 0.199 … 0.868 0.868 0.921 …
#14-10 … … 0.242 0.217 … … … 0.895 … … …
… 1/4-14 1/4-20 0.250 … 0.217 0.228 0.219 … 0.866 0.912 0.876
… … 1/4-28 0.250 … … 0.234 … … … 0.936 …
#16-10 … … 0.268 0.238 … … … 0.888 … … …
#18-9 … … 0.294 0.261 … … … 0.888 … … …
#20-9 … … 0.320 0.290 … … … 0.906 … … …
… 5/16-12 5/16-18 0.313 … 0.272 0.290 0.277 … 0.870 0.928 0.886
… … 5/16-24 0.313 … … 0.295 … … … 0.944 …
#24-9 … … 0.372 0.344 … … … 0.924 … … …
… 3/8-12 3/8-16 0.375 … 0.328 … 0.339 … 0.875 … 0.904
3.2 head type:
Fasteners made one end section increases the shape formed by the bearing surface. The provisions of the 13 standard of head tapping screws ANSI/ASME B18.6.4. Please refer to the provisions of paragraph 1.2 of B18.6.4. The thread forming and thread cutting tapping screws, 13 countersunk head in 5 - (Flat Countersunk), Oval Countersunk (oval head), pan (Pan), six and six in the head angle angle (Hex and Hex washer Head) is the most important, the five head accounted for almost 90% of the use of self tapping screws, self tapping screws should first consider the five type.
The other five kinds of other type of flat undercut (Flat Undercut), flat (Flat Trim), the margin of oblate undercut (Oval, Undercut) (Oval Trim) oblate trimming and cylinder head (Fillister for minor Hill Gang) head and head of letinous edodes (Truss), round head (Round) and 100 degrees countersunk head for the new design do not take cover, its functions can be replaced by other type, pan head can replace the letinous edodes head and head, 82 degrees countersunk head can be replaced by 100 degrees countersunk head.
Selection of self tapping screw thread rolling head and with the use of, the main consideration is flat, flat top, pan head, six head and six angle washer head five.
Drilling screws with a flat roof, flat roof, pan head and six angle washer head is most common, six head without the use of reason, because in the process of drilling, for applying pressure on a tightening tool to support a tool for drilling operations. So use cross flat, surbased, head or six angle washer head.
Although the United States national standard provides only 13 standard type, but other headforms in commercial applications can still be used, used as wall screws horn head, head to head Griddle Cake and other special design, the manufacturer can other materials manufacturing.
The surface of supporting or positioning pieces, usually by the bearing surface for loading and unloading screw. There are two basic types of bearing surface, flat bearing surface (with tie rod and cone type vertical) bearing surface (with tie rod forming angle) for the former bear in the role of the node load force in most parts under the condition of service, in addition to the continuation of the flat bearing surface of the same function, but also can be used for positioning. The conical bearing node usually refers to the buried type. Different application type, initial capacity depends on the bearing function and the transmission torque of the head.
The commonly used flat bearing bolt and bolt face types
Flat: a new design to replace round and mushroom head, low head diameter, head circumference along with high edge characteristics that make it, play a driving role for high strength of torque, and a small difference in the head head.
Round head: it is the most commonly used head type in the past
The top of the stigma: Standard surbased stigma head diameter is small, but because of the depth of the groove which is relatively high, the smaller diameter to a small area of the pressure, can be closely combined with the flange and the surface. Due to the increased concentration and to ensure the drilling mold set in the head, they can be successful the application in drilling hole.
Dome head: head under cut broadside bound and weakened part of the wire for wear, and the most widely used in electrical appliances and recorders, to bow to its sufficient bearing surface provides a type of more attractive design.
Big head: also known as the top wide elliptic head, is a low, large diameter head cleverly designed. When the additional effect of the combination allowed tolerance, can be used to cover the metal plate with larger diameter hole. Can also suggest using flat instead.
Slotted head locking head: This is a creative, once the combination is not easy to remove, but the screwdriver available standard starting. This simple design can usually solve the cost problem of portfolio, increasing the number of production and create amazing economic benefits for the manufacturing process.Six bearing angle: a fastener head wrench head has six angle head dimensions. The hexagonal hole mold completely by anti cold molding, the top of the head has a significant depression.
Six angle socket head: such as the standard six angle socket head type, but at the same time in the head base has a Chinese face, to protect the assembly to complete, so as not to wrench damage. Sometimes things are more important than appearance
Six head: This is a torque acting on the six corners of the head of the standard type, there will be a sharp sharp trimming range. To close tolerances can be recommended to the general commercial mode, and various thread diameter can also apply to the various standards. Because of the required second steps to your bearing point than the average angle of six.
Cylinder head socket head deep six angle bearing point, there is a common point of high strength bearing socket head Cap Screw. deep high torque acting on the fastener.
The twelve point: the height of the cylinder head on the Bush two points have to bear our surface fastener loads. Because of convenience for the design provides high torque, so the fastener used in high strength.
Plum: a medium height head six angle head and with lobular type washers. It includes the design of bearing surface and WASER face perpendicular to the surface of the bearing surface, the torque in the circular part (leaflet) transmission torque. The highest degree of design such use of the external drive system, the torque can play to the extreme high torque transmission. There is no change in the head itself.
Types of bolts and bolts for tapered bearing surfaces
Flat Countersunk - standard angle of 80~82 degrees; used for fastening surfaces requiring close engagement. The bearing areas provide a good center
Oval head - called "Oval Countersunk", the head shape is similar to the standard countersunk head, but more widely applied. In addition, a circular on the surface, neat, design is also more attractive.
Small countersunk head and standard countersunk head, countersunk head flat, for the 80~82, just head to the small 1/3, for simple products or special short length. In more detail, it is used for countersink standard, and is very suitable for close cooperation.
Flat Countersunk (100 degrees countersunk) - this special countersunk head screw surface is gradually applied to the requirements closely with the suggested surface to decompose pressure on the larger and less angle in soft material, especially suitable for aluminum, soft plastic.
3.3 drive system (Drive System):
Drive system, its function is to drive and transmission torque fastener will be binding and release. In the whole system, full transfer torque is such that the fastener become one of the most important points of practical. The fasteners are threaded, there are two basic types of drive system, an external drive system, a is the internal driving system. The external drive system the driving factors in the whole head, wrench work outside the internal driving system. The driving factor is at the head of the fastener, the wrench inside operation. Generally speaking, the internal drive of screw for allowing higher torque.
External drive system head shape: six angle head, six angle drive system, twelve edge drive system, etc.A groove is a groove of the oldest, the driving system of all this is the most common, there are two kinds of cutting groove manufacturing methods: one is in the head of screw to complete slotting machinery repair cut ditch, the other one is in forming forging of a molding once. The molding cut ditch more economical, because it does not require the two processing, but there are still problems in some aspects, such as the six head angle or six angle washer head using direct forming, due to depression (Indented) at the cut ditch depth is difficult to measure, the more serious will reduce joint screw and screwdriver the direct molding in the round, joint surface is unchanged, but the molding pressure will force the head diameter increased, especially on both sides of the cutting channel, using direct forming in some head, head size is difficult to control.
As a type of cut ditch depression, for all except the whole head flat edge and surbased circle are standard type, for each type of cutting groove size specified in the B18.6.4. cut ditch is especially suitable for manual combination, but not suitable for semi-automatic or fully automatic assembly. This effect depends on the driving system the head height and flatness, and flat like Gang hill, this is because the head is bigger, more deep groove cutting head, surface roughness, outer driving force will be more close to the head, the torque is more effective. In practical application, higher torque, shear is a problem even. With the deep, between the driver and the driver slotted is also very difficult to find a good fit. The gap that currently exists between the driver and the fastener, can cause not vertical. When the drive under external force not vertical, the screwdriver can damage the slotted edge caused by shear Cut. The smaller the head or the more round, the more likely this phenomenon occurs
A slot is not suitable for fast installation, such as assembly line, driving from one end of the slot screwdriver will slide to the other end, if the center line of the center of basic driving screwdriver and fasteners, drive the screwdriver. If there is no effective alignment, it will cause damage to the head, the same, may also fall to the surface of rotary drive screwdriver. The direct effect of causing damage to the fastener, with the need to increase the torque. The requirements to prevent shear loading.
Slotted production does not exist, but in most cases, also really need second slot forming effective driving screwdriver is currently no problem. Most slotted for those who do not require high torque, especially those in need of unloading and adjustment in many different environment, the best adjustment screw example is the carburetor. Similarly this groove is also commonly used in the easy consumption, need repair and remove the fasteners, such as lawn mowers, rotating equipment and so on.
Due to the extensive use of automated assembly developed some depression head, which retains the high torque, easy operation and high speed assembly, at the same time there are many heads used to be quite common, B18.6.4 recognized them as the standard. The three types are the cross points, respectively, I (Philips), cross IA meters the word (Pozidriv), II (Frearson). Please refer to the provisions of 18.6.4. The size of II is the earliest development, followed by type I, type IA for the modified I type, the type I and type IA is the most common type, II is less demand.
Cross recessed from the cross slot point category, like crossroads. The middle cross groove edge inclined to the bottom of the trough, usually located in the head of the fastener center. It is relatively deep, can help the driver driver correction. Sometimes the groove depth has reached the fasteners of the neck, in this case, the ultimate strength of the fasteners are the potential to weaken. It applies only to the torque from low to need, because it cannot avoid slipping out, which is caused by the groove edge. In total, 1.7 pounds per square inch - 1 pounds of torque, torque will not cause slip out, but more than this value in the cross slot, will lead to vicious spiral slide out. Many times, this will make the vicious spiral groove fastener completely lose the ability to work. This will also cause the loss of driving the vicious spiral screwdriver, in many cases will shorten the life of the tool And increase the cost. The cross slot have good correction, suitable for automatic assembly line. There is no problem in the production, the head forming a shape, do not need to do second times. A wide range of applications. Processing tools suitable for manual and automatic assembly line of low torque requirements of the market, for example: thin to thin steel plate steel plate, steel sheet to cork, soft plastic.
FREARSON RECESS is a kind of cross slot, commonly known as "Reed & price" slot. (see 18.6.4 II provisions) the design is very similar to the cross slot, but the edge of the groove is vertical, and the bottom is sharp. Because of these subtle differences, FREARSON drive has better performance than the cross slot. But also has some disadvantages, there will be a slip phenomenon. This system can be used to drive to low torque requirements of the market, the greater torque, trough and tool damage degree, the production of no problem.Because of this drive system application is not very extensive, the corresponding drive supply is limited, in assessing the need to consider this point. Those who cross slot to use the place, FREARSON can also be used in some occasions, not suitable for cross slot, can also be used.
Mi groove is a cross shaped slot hole, which is developed to overcome the two groove defects. The basic design is similar to the cross slot, but with additional grooves, commonly known as "ribs". It is suitable for low to medium torque requirements of the market, compared with the previous two slot is good change greatly, can greatly reduce the probability of sliding out. Rice word slot also requires end-loading to prevent slipping, but can withstand higher torque and will not damage the tank and driving screwdriver. Due to its basic design similar to the cross slot, also has a good center degree, suitable for automatic assembly line. The forming process of the M word the groove is similar to the cross slot, but also in the head forming a forming, need not second times. The processing tools are easy to obtain, but for best results, use special tool slot M word, some people try to drive the tool with a cross slot, but the effect is not good. Because of the M word The superiority of the slot, the two slot that can be applied to occasions, it can be used. But it can also be used for large torque, such as heavy plate and sheet, thread cutting machine and thread forming machine, plastic fastener materials, and automatic machine requires low torque of the screw.
The six angle hole socket drive system as his name indicates, with a hexagonal hole in the head of the fastener, the commonly used Socket head cap screws ", a kind of high strength fasteners. Six point angle suitable for high torque drive system. In this situation, slide out is not a problem, but because of driving combining with the characteristics between the wrench and fasteners, only a few times, and points will be deformed. In order to ensure the wrench with hole and tool dimensions have a general tolerances, but it can only reduce the actual contact surface, and the facilities loss. This type of fasteners, the price is higher, if used in the regular removal those who need the market, will greatly increase the cost of production. There is no big problem for the process, once formed. Before this, the six angle hole after two - Drilling and punching forming process. The applicable tool called" six angle wrench ", divided into two categories, The short and long arms. Six angle wrench is hexagonal steel rods are bent into a L shape, for a fixed size, the proportion of the length of the long arm wrench is bigger than the short arm wrench, no problem. Its effectiveness in automatic assembly line, will be driven by six. Six point angle angle screwdriver is commonly used for high torque occasions. Whether the ideal usage depends largely on the number of repeated use, for fasteners need frequent disassembly, it is not economical, because the trough and tool deformation, increase the cost. Six points for multi angle high strength fasteners and medium-sized equipment and heavy equipment for assembly.
The six corners of the pit (SPLINE RECESS dentate) basically is circular, the socket has six rectangular rib and fastener axis. Application of six head and six toothed angle angle head is the same, is used for high torque applications. Its design is the six angle and head the tool wear is reduced to the minimum. The main disadvantage is in the six corners of the dentate head head and manufacturing tools. The pit because of its complex design, must be formed in the fastener head. Due to its many sharp angle, so the production is extremely difficult to control in the required tolerances. The short life of the tools used in the production of manufacturing head in general, it will increase the cost for the production of fasteners. Driving tool, also have the same problem. Because the supplier is limited, six point angular driving tool toothed than any of the foregoing driving tool to buy. Six head used in high angle serrated twist Moment
Occasions, however, often cause supply problems due to manufacturing difficulties - especially when demand is large. The supply shortage should be taken into consideration when selecting a drive system
TORX RECESS (plum head): plum pit is Camcar company design patent. It is designed to solve the problems existing in the system. All of the above head drive plum head is a six angle blade design, with straight edges and the head is shallow. This design is supported by torque rather than most of the head point support. Improve the efficiency so that the transmission of torque. The straight edge can eliminate the sliding trend under torsion and end load. These are the plum pit in practice has the best combination drive to transfer torque. In fact the plum blossom head general than other head shallow, which means that the tightening force does not produce because of head loss this design has a depth. Their excellent characteristics make it become the ideal tool for automatic assembly line in manufacturing. No problem. Head is formed in the heading process. Due to the plum with head Many arcs, rather than right angles, make tools wear less obvious. Tight tolerances guarantee the maximum combination
The head has a plurality of patent business clubs can provide a variety of products for users. Tools available from many sources. The head of any torque plum application requirements, both are very suitable for manual or automatic assembly design. It can eliminate the sliding, it can transfer more torque, head life and manufacturing tool life long. These advantages can reduce the cost of fasteners. Meihua head can be applied to large torque applications, especially for repeated use, such as heavy machinery and equipment. The head can be used for automatic assembly. This is because the head is not due to deformation and need to return to work, the tool has a long service life, fatigue caused by operation workers the error and thus also reduced. In the application and the auto industry, the head is more and more popular. The head is suitable for almost any occasion of high-speed assembly.Six: six angle angle drive system is a universal type and is widely used. It is used for automatic assembly. The variety of torque requirements for low torque, high torque applications. On occasions, with six head angle problem is the same. So the fastener head will deform and drive tools will wear crack. Due to the pressure of life, for driving six head sleeve is often very short. This will greatly increase the cost of fasteners.
There are six head two types of drive system. Their different manufacturing. Six hexagon socket head (INDENT HEX) is a kind of economic type. It is also forming heading, no two times. The whole process margin of six head (TRIMMED HEX) is a relatively expensive. ", the second processes six angle surface. This will allow more sharp angle, favorable performance and beautiful appearance. In addition, six head two types will sometimes head slot, this can also be used when necessary driving screwdriver.
Driving tool quite popular. The six angle suitable for manual, automatic assembly, low torque applications. Rated torque must remember. When the fastener driving tool and its deformation, the rest of the system should be reexamined. The six hexagon head fasteners in various steel plate assembly is very useful.
Twelve row: Twelve head edge driving system is high strength of the external wrench system is mainly used in aircraft industry. Twelve arris design is cylindrical with appropriate vertex - as the name based on referring to - twelve edges. When used in the aircraft industry, the height of 2/3 along the center of the head to the drill head height to reduce weight. The twelve main edge for high strength fasteners. The fasteners used in high torque applications. This is the head of the driving sleeve using the same structure. Twelve edge system is generally better than six angle system, but the disadvantage is the same. Fastener driving combination is mainly in edges and not on the surface. When used repeatedly, edge easy to wear and rounded the fastener torsion motionless. Another disadvantage driving sleeve. Because the structure of fasteners to withstand the torque reaction in the inner wall of the sleeve and lead to cracking. The fastener itself is very expensive, the Increase the cost of manufacturing. The disadvantages are twelve edge structure than the structure of many other types of difficult, but it is also in the head forming. Can get the driving tool. Twelve edge driving system for high strength commercial applications. Especially for COUNTERBORE applications, heavy machinery and equipment and aircraft.
Mei Flower outside: Plum drive system is suitable for all occasions. Driving wrench plum type driven design is parallel to the six angle leaflike, fastener axis straight edge, moderate height. At the time of driving leaflike surface contact rather than most other drive system for point contact. This makes the driving torque transmission more efficient. Plum outer drive the system can be used for any torque requirements, but it is the most suitable and high torque applications. It is fast, convenient and automatic driving tool and combination makes it very suitable for automatic assembly type outer plum like other outside type sleeve drive. Because it is a supporting surface transfer torque effectively, the sleeve basically will not be damaged. It saves the driving tool cost, thereby greatly reducing the cost of a large number of high-speed, fastener application. The fastener head even after repeated use never deformation. This saves in the assembly The cost of fasteners, service and rework. Meihua head design easily in the strict tolerance in molding process, all manufacturing has no problem. Tools are also available from several large well-known suppliers. This type of automatic assembly is to solve the problems including tool damage and fastener deformation method. Suitable for manual drive plum or automatic assembly requirements of high torque applications. Most of the plum blossom heads for assembly, automotive, heavy machinery and equipment. Very suitable for wobbler thread cutting and thread forming screws. When excess torque is needed. Wobbler use is varied.
3.4: to ensure the length of the screw thread and the screw completely combined with the thickness of the length of the screw in the assembly process, selection is very important. The average length of the screw should be equal to the combined length (total thickness component) plus screws. At the end of the tail end is completely non screw thread part and screw type screw into AB or BP type cone tail length or drill screw drill tail length. These different cone drill tail or tail length of each standard stipulated in Appendix B18.6.4, and its calculation formula.
For example, we will use the 1/4 "-20 pan head tapping screw thread forming to assemble a 0.25" thick and 0.21 "thick plate, screw at the end of the maximum length is 0.175, the length of the screw tolerance is +0 -0.03. Then the screw length should be 0.25+0.21+0.175+0.03 = 0.665. So we should use 3/4 screw length. This combination the length of exposure to the other end of the 0.75-0.21-0.25 = 0.290, the self tapping screws generally suitable for increase in the length of the 1/8.
4 materials, heat treatment, mechanical properties and processing requirements of the final: screw can be made of carbon steel, stainless steel, copper or aluminum manufacturing. Carbon steel tapping screws accounted for the vast majority, even more than 95%, iron and steel materials outside the material of the self tapping screws tight in JIS B1055 2 in the affiliated book of mechanical properties (hardness and torsional strength) regulations no, the rest of the national standard or other recognized standard for mechanical properties in general by the purchaser and manufacturer agreement. So the problem discussed in this paper, almost concentrated in carbon steel.4.1 material: carbon steel tapping screws made of low carbon steel, when requested by the customer, are made of carbon steel in use. But most of the use of C1018 - C1022 material (this is because the carbon content in more than 0.15% plays a role in heat treatment). Raw materials, mostly by wire or spheroidal annealing to fine line extension process to comply with its provisions. The molding conditions of material composition are as follows:
English 1 self tapping screw material chemical composition
Specification for self tapping screws, 2 component limit,% by weight%
Carbon manganese
# 4 or less in furnace 0.13 - 0.25 - 1.65 of 0.60
Products are examined 0.11 - 0.27, 0.57 - 1.71
# 5 to 1/2 inches furnace 0.15 - 0.25 - 1.65 of 0.70
Products are examined 0.13 - 0.27, 0.64 - 1.71
1. metric screws have no special requirements and limit their chemical composition
2. furnace analysis provides only order information. Products are examined for consideration of carbide segregation in the core of the screw
4.2 heat treatment: tapping screws need to be treated by carburizing heat treatment to obtain very hard surface for threading, forming or cutting. After carburizing and quenching and tempering, the mechanical properties required by the specification are:
Surface hardness: general self tapping screws should be 45 HRC above the surface after carburizing hardness, so as to be able to score. The surface hardness and iron core hardness drilling screws to a little higher than the general self tapping screws (J78 required surface hardness must be 50~56HRC), this is because the drilling screws more than a drilling operation. In order to achieve the purpose of inspection or testing the daily fast, surface hardness can be used HR 15N, Knoop's micro hardness examination. Or micrograms of these methods depends on the choice of products can be tested area size. The product surface treatment should be slightly, and then test the hardness value. If the hardness value is lower than the specified method, can refer to the following description location: 0.002 inches Knoop or 300g 500g load of micrograms's micro hardness tester reads the hardness value of the surface of the product, if the carburizing depth is 0.004 inches and below, you can use the 100g load on the surface 0.001 inch position test. When the detection of surface hardness and carburizing depth, to ensure that the embedded material can be properly supported, reading from from the center to the center line within the range of more than a longitudinal measurement. The samples should be properly embedded in the supporting material. The outer diameter of testing under microscope. The amount of the sample truncation surface, at least the original sample diameter of more than 95%.
Carburizing depth: the depth of carburizing carburizing is quite important, too shallow, not the correct screw assembly, carburizing too deep, torque and extension of the center will be affected. The general self tapping screw depth of carburizing tests shall be at the midpoint of the screw section (at least the original sample diameter above 95%) point on the Asan measuring 2702, ISO ST 3.9 screws can be less than the provisions in the valley to the center of the tooth measurement.
Hardness of the core after tempering: the hardness of the core should be measured at the midpoint of the radius of the tooth to the radius at the bottom of the complete tooth (parallel) near the end of the screw section
In view of metallographic microstructure, surface and center shall have no banded ferrite. The ferrite appeared said incomplete heat treatment (heating temperature; or the quenching speed is too slow to ferrite first on the grain boundary). For strength requirements may reduce its characteristics.
Requirements for hardness of metric triangular self - tapping screws after heat treatment: mm
Request item size SAE J1237 DIN 7500
Surface hardness, all sizes 45 HRC Min., 450 HV Min (1)
Heart hardness, all sizes 28 ~ 38 HRC, 240 ~ 370 HV (2)
Carburizing depth M2 ~ M2.5 0.05 ~ 0.18, 0.04 ~ 0.12
M3 ~ M3.5 0.05 ~ 0.18
M4 ~ M5 0.10 ~ 0.23 0.10 ~ 0.25
M6 ~ M8 0.13 ~ 0.28 0.15 ~ 0.28
M10 0.15 ~ 0.32
M12 ---
Requirements for hardness of metric wide tooth self tapping screws after heat treatment: mm
Request item size ISO 2702, DIN 7504, DIN 267/12, JIS B1055
Surface hardness, all sizes 450 Min (1), 560 Min (1), 450 Min (1), 450 Min (1)
Heart hardness, all sizes ranged from 270 to 390 (3), 270 to 425 (2), 270 to 390 (1), 270 to 390
Carburizing depth ST2.2 ~ 2.6 0.04 ~0.10 --- 0.04 ~0.10 0.04 ~0.10
ST2.9 ~ 3.5, 0.05 ~ 0.18, 0.05 ~ 0.18, 0.05 ~ 0.18, 0.05 ~ 0.18
ST3.9 ~ 5.5, 0.10 ~ 0.23, 0.10 ~ 0.23, 0.10 ~ 0.23, 0.10 ~ 0.23
ST6.3 ~ 8, 0.15 ~ 0.28, 0.15 ~ 0.28, 0.15 ~ 0.28, 0.15 ~ 0.28
(1) use HV 0.3 load test. (2) use HV 0.5 load test. (3) ST3.9 (including) use HV 5 load test below,
Use HV 10 load test for ST4.2 (above)
Hardness requirements for British self tapping screws after heat treatment
Request item size SAE, J78, SAE, J81, SAE, J933
Surface hardness all sizes 50 ~ 56 HRC 45 HRC Min. 45 HRC Min.
Heart hardness, all sizes 32 ~ 40 HRC, 28 ~ 38 HRC, 28 ~ 38 HRC (2)
The carburizing depth (1) # 4 to 60.002 - 0.007 #"
8 to 120.004 - 0.009 # #"
1/4 or above 0.005 - 0.011"
(1) the test position of full carburizing depth shall be on the thread of the screw and between the Asan and the bottom of the tooth. When using the 500g load, it will be small and hard
When the read test value is converted to HRC value, the maximum carburizing depth shall not exceed 42 HRC.
(2) hardness shall not exceed the maximum value, and preferably not greater than Rockwell C36, to ensure that the assembly and use without damage
4.3 surface treatment: most of the surface is covered with self tapping screws using galvanized or zinc phosphate coating. Cadmium plating because of its high cost and toxicity so rarely, if the appearance is very important, you can choose nickel or chromium. Surface treatment will have two problems: one is that surface treatment will not only increase the size (e.g. cavity narrowing) and surface treatment of torque, tightness, intensity, so the scoring test shall be in accordance with the zinc, cadmium plating or phosphate treatment do different requirements. In the test for attack drill aperture, the screw must be used with a surface treatment of screw. The small size, high hardness, the self tapping screws often due to hydrogen embrittlement failure. Led to the use of self tapping screws to iron scored, had to carburizing. In carburizing process will produce high hardness and high carbon content, when this situation Hydrogen embrittlement is produced by electroplating or pickling treatment. The method recommended in the specification is to eliminate hydrogen embrittlement:
A) bake after 1 hours of plating or pickling
B) temperatures ranged from 375 to 425 oF (190 ~ 220 oC)
C) time is at least 4 hoursHydrogen embrittlement test: hydrogen embrittlement test is to test whether the residual hydrogen and self tapping screws will make screw screw in brittle tissues (usually brittle not suddenly occurred, and shall be given a certain stress will appear) plating or clad screws should be installed as shown in Table 3 the provisions of the test plate and steel flat washers, bearing surface using standard outstanding head screws under the head of flat washers, countersunk screw type (Oval) using a combination of the chamfered steel sheet. The maximum interval invalid tooth length installed in the head bearing surface of flat washers or spacer thickness can meet the screws. For half tooth long screw shank can be used longer cold steel spacers or flat WASER support, in order to ensure full tooth part can be combined and maintained in the test thickness. The screw should be locked to a maximum breaking torque 80%, breaking torque Is to lock the 5 screws to break determined by the average value, continue to maintain a lock for 24 hours, then loosen the screw rotation after locking screw torque to the original, there should be no obvious failure.
Note: the torque values specified in the thread of the tapping teeth are specified in SAE, J81 and J1237
5 the function of self tapping screws: the functionality of self tapping screws includes extensibility (Ductility), scoring test (Drive, Tese), scoring torque (Drive, Torque) and Speed (Drive), etc. as described below:
Ductility (Ductility): screw carburizing treatment, quenching, tempering, in order to avoid due to improper heat treatment leads to excellent and fragility caused by broken, usually required to test its ductility (toughness). Test method for screw placement of a tested sample and showed a hardening seat angle in, or other appropriate equipment, according to the ASME B18.6.4 cavity test seat than the nominal diameter of large screw shall be 0.020 - 0.040 inches (0.5 - 1.0mm). With axial pressure on the top of the screw head, pressure should be continued until the head bearing surface and the screw axis of an angle. The permanent bending test can be used Lang tou repeated blows until permanent bending. If the head part of the rejected
The ductility test angle specified by each specification
F.I.P.
1000 SAE
J78 SAE
J81 ASME
B18.6.4 SAE
J1237 JIS
B1055
10O, 5O, 7O, 10O, 10O, 10O ~ 15O
(Drive Tese): scoring test scored test for the main characteristics of the self tapping screws, self tapping screws cannot be combined when scored in iron will lose its main function. So the rules are required to do the test scored.B18.6.4 sets the tail type AB, B, BP, C, D, F, G and T (BF, BT, BG) must be assembled on the test. In the test, the screw must be screwed into a prescribed thickness and hardness, diamond plate pre drilled in precession when thread without deformation can be visually, in the test without torque limit. As for the screw teeth of the triangle (see SAEJ78. J1237, FIP 1000, DIN 7500) in the assembly and testing, not only requires the precession when no thread deformation can be visually, but also provides the torque assembly test limit.
Specification for self - tapping screws for inch size and bore size
Self tapping (wide tooth) mechanical teeth
Type, A, Type, B specifications, Type, D, F, G, T, Type, TT
(triangular tooth)
Specification plate thickness, aperture size, plate thickness, aperture, plate thickness, aperture, plate thickness, aperture
#2-32 0.048 0.076 #2-32 0.048 0.076 #2-56 0.078 0.073 0.125 0.075
#3-28 0.048 0.081 #3-28 0.048 0.081 #3-48 0.094 0.081 0.125 0.087
#4-24 0.048 0.086 #4-24 0.048 0.086 #4-40 0.109 0.096 0.125 0.098
#5-20 0.048 0.107 #5-20 0.048 0.107 #5-40 0.109 0.101 0.125 0.110
#6-18 0.075 0.116 #6-20 0.075 0.116 #6-32 0.140 0.120 0.125 0.120
#7-16 0.075 0.129 #7-19 0.075 0.129 … … … … …
#8-15 0.075 0.136 #8-18 0.075 0.136 #8-32 0.140 0.147 0.188 0.147
#9-14 0.075 0.149 … … … … … … …
#10-12 0.125 0.159 #10-16 0.125 0.159 #10-24 0.188 0.173 0.188 0.166
… … … … … … #10-32 0.188 0.177 0.188 0.172
#12-11 0.125 0.188 #12-14 0.125 0.188 #12-24 0.188 0.199 … …
#14-10 0.125 0.217 … … … … … … …
… … … 1/4-14 0.1875 0.217 1/4-20 0.250 0.228 0.250 0.219
… … … … … … 1/4-28 0.250 0.234 … …
#16-10 0.1875 0.238 … … … … … … …
#18-9 0.1875 0.261 … … … … … … …
#20-9 0.1875 0.290 … … … … … … …
… … 5/16-12 0.1875 0.272 5/16-18 0.313 0.290 0.312 0.277
… … … … … … 5/16-24 0.313 0.295 … …
… … 3/8-12 0.188 0.328 3/8-16 … … 0.375 0.339
1. requirements of iron plate are made of low carbon steel below 0.23%, thickness tolerance + 0.002; bore tolerance + 0.001; hardness 70 ~85 HRB.; dimensions refer to ANSI B18.6.4; FIP 1000; SAE J81; J933.
The plate size used by 2.TYPE C is the same as TYPE A
Metric specification for self tapping screws test for iron plate thickness and bore size
Self tapping (wide tooth) mechanical tooth (triangular tooth)
DIN, 267/12, JIS, B1055 specifications, DIN7500, SAE, J1237
Specification plate, thickness, aperture, plate thickness, aperture, plate thickness, aperture, plate thickness, aperture
ST2.2 1.3-1.2 1.96-1.91 1.30-1.17 1.955-1.905 M2 2.0 1.8 3.0 1.77
ST2.6 -- 2.235-2.185 M2.5 2.5 2.3 2.25
ST2.9 1.3-1.2 2.47-2.42 2.465-2.415 M3 3.0 2.75 2.70
ST3.3 -- 2.730-2.680 M3.5 3.5 3.2 3.15
ST3.5 2.1-1.9 2.98-2.93 2.06-1.85 2.970-2.920 M4 4.0 3.6 5.0 3.60
ST3.9 3.29-3.24 3.290-3.240 M5 5.0 4.6 4.55
ST4.2 3.49-3.44 3.480-3.430 M6 6.0 5.5 6.0 5.40
ST4.8 3.2-3.1 4.08-4.03 3.23-3.10 4.065-4.015 M8 8.0 7.4 8.0 7.30
ST5.5 4.79-4.74 4.785-4.735 M10 10.0 9.3 10.0 9.20
ST6.3 5.1-4.7 5.53-5.48 5.05-4.67 5.525-5.475 M12 -- -- 12.0 11.00
ST 8.0 6.94-6.89 6.935-6.885
JIS B1055 has a low carbon content of 0.23% steel and a hardness of 70 ~ 85 HRB (125 ~ 165 HB)
The iron plate of SAE J1237 is made of low carbon steel with a hardness of 75 ~ 90 HRB with an aperture tolerance of + 0.025mm.
The hardness of DIN 267/12 iron plate is 72 ~ 87 HRB. The thickness and bore tolerance of iron plate of DIN 7500 are not specified
Requirements for maximum rotational torque test of various specifications
Dimensions DIN, 7500, SAE, J1237, FIP 1000, dimensions SAE, J81, FIP 1000
N.m N.m lb-in lb-in lb-in
Phos. Zinc Phos. Zinc Phos. Zinc Phos. Zinc
M2×0.4 0.3 0.4 0.6 4 5 # 2-56 4.5 6 4.5 6
M2.5×0.45 0.6 0.8 1.0 7 9 # 3-48 7.5 9.5 7.5 9.5
M3×0.5 1.0 1.3 1.7 11 15 # 4-40 9 13 9 13
M3.5×0.6 1.6 1.9 2.4 17 21 # 5-40 12 16 12 16
M4×0.7 2.4 2.6 3.4 22 30 # 6-32 14 20 14 20
M5×0.8 4.7 4.8 6.0 42 53 # 8-32 25 32 25 32
M6×1.0 8.0 7.5 9.2 66 81 #10-24 35 52 35 52
M8×1.25 20 16 20 142 177 #10-32 -- -- 35 52
M10×1.5 39 28 35 248 310 1/4-20 90 120 90 120
M12×1.75 -- 46 55 -- -- 5/16-18 180 240 180 240
3/8-16 240 300 240 300
Standard Specification for torque strength of metric self tapping screw mechanical teeth
Size DIN 7500 SAE J1237 FIP 1000
TY., F, T, triangular teeth
N.m Min N.m Min lb-in Min lb-in Min
M2×0.4 0.5 0.7 4 6
M2.5×0.45 1.0 1.2 10 11
M3×0.5 1.5 2.2 18 19
M3.5×0.6 2.3 3.5 27 31
M4×0.7 3.4 5.2 41 46
M5×0.8 7.1 10.5 83 93
M6×1.0 12 17.7 142 157
M8×1.25 29 43.0 354 380
M10×1.5 59 87.0 -- 770
M12×1.75 -- 152.0 -- --
Requirements for torque strength of metric self tapping screws (wide teeth)
Size ISO 2702, JIS, B1055, DIN 7504, DIN, 267/12
Min. Nm Min. Nm
ST 2.2 0.45 -- 0.45
ST 2.6 0.90 --
ST 2.9 1.50 1.50
ST 3.3 2.00 --
ST 3.5 2.70 2.80
ST 3.9 3.40 3.40
ST 4.2 4.40 4.50
ST 4.8 6.30 6.50
ST 5.5 10.00 10
ST 6.3 13.60 14
ST 8.0 30.50 -- 31
4.3 SAE J81 :
六角及六角华司头 (有足够长度) 螺丝需作垂直抗拉强度测试. 另外尚需加测旋紧负荷, 保证扭矩. 测旋紧负荷时螺丝应组装在一与组装测试相同之钢板上用力旋紧至规定之扭矩值. 扭矩值应略为超过扭矩测试扭矩规定之下限. 在承受此种扭矩下, 螺丝不应破断.
所有螺纹成型螺丝应做延展性测试, 将螺丝头弯曲与轴呈7度角. 同时电镀螺丝应作氢脆化测试, 将螺丝依规定之扭矩旋入预置孔旋紧并保持24小时而螺丝不断头者合格 (此值约等于扭矩测试规定下限之75%).
最后一个定义是j81承认
4.4 SAE J78 :
4.5 FIP 1000 :
5 screw selection and application:The screw force can be assembled called screwing torque (Drive Torque) - forming and tapping or mating threads, if sustained in force conditions, will screw seal tightly, and continue to be more than - called the ultimate torque (Utimate Torque) - screw will have broken off. Rip (thread slipping) or self with workpiece prolapse.
In the use of all screws before, the most important question is: "what is the correct tightening torque? How much torque so that the screw can be tightened without causing screws or combining the workpiece damage?". It is obvious that the inevitable tightening torque between screwing torque and ultimate torque between them. And there is no reason to recommend two point. There are several factors influencing rotation torque and ultimate torque, the more important factor is the screw type, size, composition and hardness of the workpiece, workpiece thickness and pre drilling preparation methods, the most controversial is pre drilled with screw size, interestingly, other factors will influence the size of pre drilled. Therefore pre drilling is the design factors of the final decision, but also the most important. If the pre drilled hole too, can be easily screwed into the screw, but will destroy the integrity of the lead screw in combination Not to limit torque is generated from the pre drilling. If the hole is too small, then screwing torque will increase even broken danger. Even if the screw has been closed and tightened, but in the screwing torque and ultimate torque is too small difference may lead to combination of failure.
The torque caused by various factors affecting the pre drilling shall be determined in accordance with the torque and the limit torque"
5.1 screw type:
In general, we can easily make use of environmental factors to decide whether to use thread forming, thread cutting, thread rolling or tapping screws:
- screws must be combined with an external load, or not?
- what are the binding materials? Steel, cast iron, aluminum, plastic, wood or other?
- what is the thickness of the binding piece?
- screws used for through holes or blind holes?
For example, is it important to clean the hole through perforation?- can it be acceptable for tapping, chipping or drilling?
- the processing system for the preparation hole, drilled, cut, struck or forged?
- assembly of screws, manual assembly, semi-automatic or fully automatic assembly?
- do you need disassembly after the combination?
- is the environment corrosive?
- what is the cost of the screw? What is the cost of the assembly?
The same size called self tapping screw thread and thread the wide Machinery Department of teeth with different diameters. In general, prepare pore size is not the same, usually, we only need two groups of different sizes of prepared hole, a group is suitable for mechanical screw thread forming and thread cutting tapping screws, another group of wide screw thread forming and thread cutting tapping screws. Thread rolling and thread forming screws for hole can also be used for thread cutting screws, this is because in all conditions are the same, the cutting torque is less than required for forming the required torque.
5.2 screw size:
In combination with structure, good design is usually recommended if the combination of bolt and nut in combination work force is too large or the use of stress load is too large to cause of failure, should make the bolt breaking and the thread should not tear. The same idea as suitable to assemble. Special tapping screws are used in a the stress load situations. If the combination failure should be broken and non screw thread broken or pulled out.
The resistance of screw thread damage and pulled the function by the strength of the material and the thread shear stress area, in other words, the screw thread size, overlapping depth control and matched thread length, thread length is equal to the combined thickness of the workpiece. The thread depth determined by preliminary aperture overlap, another determinant of screw size is decided the torque and tensile strength.
In any combination of thickness, the size of the screw will increase the tensile stress and shear thread load area ratio of the stress load area increases, often leads to tear or pull. Such as reducing the thread screw size ratio decreased, but will increase the torque caused by screwing screws broken, so how to balance the tensile strength to resist tear or pull on the workpiece thread to determine the size and thickness of the screw used.
In a steel unified thread fastener, we usually find the thread length is approximately equal to twice the fastener with the diameter of D, used to prevent the thread rip, the screw thread cutting, also seems reasonable. Because the full path and the minimum diameter of pre drilled nut, screw size is equal to or less than the thickness of the material can be prevented thread the rip. Practically, the tapping of the screw thread cutting resistance force is small, can be used in 1.5 or more times the diameter of thick materials. And thread rolling screws because of resistance, it is recommended to use 1.1 times the diameter of the material thickness. The thread forming screws, because of its wide use thread and high torque. It is very difficult to decide to use the size of screw thread to prevent rip or pull out. Fortunately, most thread forming screw are rarely used in high load situations, therefore, in preventing thread or tear It is a reasonable choice to pull out material with 1.3 times diameter
Let us take a case to make a summary: if we use the thickness of the material is 0.125, so we first consider the #6 thread rolling screws (1.1x.125=.137), #5 (1x.125=.125), thread cutting screws #8 thread forming screw thread. The tear or pull concerns for the occasion, #6 thread rolling screws the use of material thickness not less than 0.125 "(.138/1.1), #6 thread cutting screws 0.138" (.138/1), #6 thread forming screw 0.106 "(.138/1.3).
The above recommendations are based on the iron plate, while the use of other materials should be adjusted relative to the effect of shear on the material. Above all, the proposed method assumes that the pre drilled hole is of the standard size5.3 material hardness and thickness:
Obviously, the greater the hardness of the material or the greater the thickness, the greater the torque required. Therefore, the pre drilling needs to be increased, but the adjustment of the pre drilling size limit can only be adjusted to a fairly narrow range
The appropriate aperture is usually about screw threads to keep drilling screw tapping point overlap, but not to large aperture thread height above 75%. In the small screws, there are some possible adjustment. Such as the #8 width of thread height of only 0.022. "Such as aperture that provide only half height screw thread thread cutting screws into the components of the composite high", and only 0.011 thread forming and thread rolling screws because of the extrusion thread of laminated high a little more. To the height of 75% aperture thread thread thread cutting screws into the components of the composite high ", and only 0.005 thread forming and thread rolling tapping screws should not be too many. It said the adjustment range of diameter of only 0.010.
For stiffer or thicker materials, larger screws should be selected and lowered by torque, rather than by increasing the aperture to allow smaller screws to be assembled
[statement] the publication of this article by the Chinese screw business college does not mean that it agrees with the statement or description, but only to provide more information
All the publications are in charge. Reprinted please indicate the author's name and source.
Performance Specification for F.I.P 1000 (Fastener, Inspection, Products) self tapping screws
Liu source: Joe Greenslade 2005-09-06 browsing frequency: 7713 times
F.I.P 1000 (Fastener, Inspection, Products)
Performance Specification for self tapping screws (Tapping, Screw, Performance, Specifications)
1 ductility test
1.1 scope of application: all kinds of self tapping screws
1.2 test purposes: check the product in assembly, rotation or tightening, or in the process of impact stress, the risk of head brittle fracture
1.3 test device: A. ductility test base. B. small hammer.
1.4 recommend minimum test volume: 8 batches per batch, no more than 250M PCS. per batch
1.5 test program: A. screw placement test hole seat within the appropriate.B. to hammer head to hit test of bearing surface and the seat surface with measuring seat. C. check.
1.6 bad: if the head is completely separated from the screw handle, the test is bad
1.7, product adverse factors: A. heart hardness is too high. B. carburized layer is too deep. C. punching too deep
D. the inside diameter of the head is too small
2 torsion strength test
2.1 scope of application: all kinds of self tapping screws
2.2 Test Objective: to check the product because of insufficient torque in the assembly rotates or screwing off.
2.3 test device: A. screw clamp. B. clamp holder,.C. screw, fixed seat.D., torque wrench within 2% accuracy
2.4 recommend minimum test volume: 4 batches per batch, no more than 250M PCS. per batch
2.5 test program: A. screw placement test fixture and fixture placement fixture support seat, screws should be at least two teeth in the fixture, two teeth in the fixture. B. will support the determination of the fixed seat is fixed on the seat. C. torsion wrench until the screw off. D. record damage value.
2.6: screw wring value below a predetermined value.
2.7, product adverse factors: A. heart hardness is too low. B. surface hardness is too low. C. effective carburizing layer is less than.D., the minimum path (tooth bottom diameter) is too small
3 scoring test
3.1 scope of application: all types of self tapping screws except Type 25
3.2 Test Objective: to check whether the product is due to the assembly due to the combination of thread collapse failure.
3.3 test device: A. test steel plate. B. torsion tool (use electric tools, but not more than 500rpm)
3.4 recommend minimum test volume: 4 batches per batch, no more than 250M PCS. per batch
3.5 test program: A. screws into the test plate until the first complete thread through the plate, Plain screw can be a little oil.B. check thread is collapsing.
Note: this test can be carried out with the screw torque test and the hydrogen embrittlement test
3.6: screw thread broken.
3.7 adverse factors: A. effective. B. carburizing hardness of carburized layer is too low. The C. test.D. test plate is too hard so small.
4 torque test
4.1 scope of application: thread rolling (triangular tooth), self tapping screw
4.2 test purposes: check that the product is difficult to assemble due to excessive twisting torque during assembly
4.3 test device: A. test steel plate. B. torque wrench with a precision of 2%
4.4 recommend minimum test volume: 4 batches per batch, no more than 250M PCS. per batch
4.5 test procedures: A. screw the torque wrench into the test steel plate until the first complete thread through the steel plate, Plain screw can be a little oil,.B. record the maximum torque value
Note: this test can be carried out with the screw in test and the hydrogen embrittlement test
4.6 bad: screw into the maximum torque is greater than the specified value
4.7 adverse factors: A. thread rolling is not properly shaped. The hardness is too low. C. B. carburizing carburizing depth. D. test.E. test plate is too hard so small. F. products need to oil or wax.
5 hydrogen embrittlement test
5.1 scope of application: all galvanized self tapping screws
5.2 Test Objective: early detection to prevent plating hydrogen embrittlement in self tapping screws for locking 24 hours after the collapse.
5.3 test device: A. test steel plate. B. precision torque wrench in 2%.C. plane China
5.4 recommend minimum test volume: 8 batches per batch, no more than 250M PCS. per batch
5.5 test program: A. with the average torsion strength as a benchmark, will be multiplied by 80% for locking torque of.B. flat WASER will set into the screw screw is screwed into the test plate, to tighten locking torque, and placed 24 hours.C. to loosen the screw after screwing the locking torque.5.6 bad: from the beginning of the test to the end of the test, there must be no screw broken ends
5.7 adverse factors: A. plating after drying. B. screw tight locking torque Zhisuo too high. C. is not set into the washer clamping torque caused by too high. D. hole too deep.
6 attack speed test
6.1 scope of application: only for self drilling screws
6.2 test purpose: to find out that the drilling speed is too slow or the drilling problem is caused by production problems
6.3 test device: A. attack speed test machine. B. test steel plate, thickness 0.060 - 0.064, hardness HRB 60 - 85.
6.4 recommend minimum test volume:
A. 5000 under 6
B. 5001-15000, 12
C. 15001-50000, 18
D. 50001-250000, 25
Note: no more than 250000 pieces per batch
E. if the above sampling test has one exceeding the minimum speed requirement, double tests shall be carried out according to the following sampling plan
The number of samples is slow, the attack speed is 1, and the slow attack speed is 2
1210
2410
3621
5031
Note 1: "slow speed" refers to the samples exceeding the maximum of drilling time but not more than two times.
2: "slow speed" refers to the samples exceeding the maximum of drilling time of two times.
6.5 test procedure: A. put the test piece on the test machine and.B. adjust the test machine so that the test machine can stop and record the penetration time when the steel plate is penetrated and more than one complete tooth. C. records the test time
6.6, bad: in accordance with the above sampling table test, the test time exceeds the specified value
6.7, product adverse factors: A. samples, drill tail burr, e. test, steel plate is too thick
B. carburizing hardness is too low, F. axial load is too tight
C. carburizing depth is not enough, G. attack speed is too slow
D. test steel plate is too hard and h. surface is too thick
7 self tapping screw test steel plate selection table
7.1 Type A
Dimensional ductility test
Minimum angle minimum torque strength
Lb-in. test steel plate (HRB 70-85)
The thickness of 0.002 aperture 0.001
2-32 10 4 0.048 0.076
3-28 10 9 0.048 0.081
4-24 10 12 0.048 0.086
5-20 10 18 0.048 0.1065
6-18 10 24 0.075 0.116
7-16 10 30 0.075 0.1285
8-15 10 39 0.075 0.136
9-14 10 43 0.075 0.149
10-12 10 48 0.125 0.159
12-11 10 83 0.125 0.1875
14-10 10 125 0.125 0.2165
16-10 10 152 0.1875 0.238
18-9 10 196 0.1875 0.261
20-9 10 250 0.1875 0.290
24-9 10 492 0.1875 0.3438
最低样本数 8 4
7.2 Type AB, B, BT
尺寸 延展性测试
最小角度 最低扭矩强度
lb-in. 测试钢板( HRB 70 - 85)
英制 公制 厚度 0.002 孔径 0.001
2-32 M2.2x0.79 10 4 0.048 0.076
3-28 10 9 0.048 0.081
4-24 M2.9x1.06 10 13 0.048 0.086
5-20 10 18 0.048 0.1065
6-20 M3.5x1.27 10 24 0.075 0.116
7-19 10 30 0.075 0.1285
8-18 M4.2x1.41 10 39 0.075 0.136
10-16 M4.8x1.59 10 56 0.125 0.159
12-14 M5.5x1.81 10 88 0.125 0.1875
1/4-14 M6.3x1.81 10 142 0.1875 0.2165
5/16-12 M8x2.12 10 290 0.1875 0.272
3/8-12 M9.5x2.12 10 590 0.1875 0.3281
Minimum sample size 84
7.3 Type F, T (23) Inch
Dimensional ductility test
Minimum angle minimum torque strength
Lb-in. test steel plate (HRB 70-85)
The thickness of 0.002 aperture 0.001
2-56 10 5 0.078 0.073
3-48 10 9 0.094 0.081
4-40 10 13 0.109 0.096
5-40 10 18 0.109 0.101
6-32 10 23 0.140 0.120
8-32 10 42 0.140 0.147
10-24 10 56 0.1875 0.173
10-32 10 74 0.1875 0.177
12-24 10 93 0.1875 0.199
1/4-20 10 140 0.250 0.228
1/4-28 10 179 0.250 0.234
5/16-18 10 306 0.3125 0.290
5/16-24 10 370 0.3125 0.295
7.4 F type, T (23) metric
Dimensional ductility test
Minimum angle minimum torque strength
Pounds. Test steel plate (HRB 70-85)
The thickness of 0.002 aperture 0.001
M2x0.4 10 4 0.078 0.067
M2.5x0.45 10 10 0.094 0.083
M3x0.5 10 18 0.109 0.102
M3.5x0.6 10 27 0.140 0.122
M4x0.7 10 41 0.140 0.138
M5x0.8 10 83 0.1875 0.177
M6x1.0 10 142 0.250 0.213
M8x1.25 10 354 0.312 0.291
Minimum sample size 84
7.5 thread hobbing (triangular teeth) English system
Dimensional ductility test
Minimum angle minimum torque strength
Lb-in. test steel plate (HRB 70-85) screw torque
The thickness of 0.002 aperture 0.001 phosphate and oil
Cadmium plating
Lb-in. galvanized
lb-in.
2-56 10 6 0.125 0.075 4.5 6
3-48 10 10 0.125 0.087 7.5 9.5
4-40 10 14 0.125 0.098 9 13
5-40 10 22 0.125 0.110 12 16
6-32 10 24 0.125 0.120 14 20
8-32 10 48 0.1875 0.147 25 32
10-24 10 65 0.1875 0.166 35 52
10-32 10 74 0.1875 0.172 35 52
1/4-20 10 156 0.250 0.219 90 120
5/16-18 10 330 0.312 0.277 180 240
3/8-16 10 600 0.375 0.339 240 300
Minimum sample size 8444
7.6 thread rolling (triangular tooth) metric
Dimensional ductility test
Minimum angle minimum torque strength
Lb-in. test steel plate (HRB 70-85) screw torque
The thickness of 0.002 aperture 0.001 phosphate and oil
Cadmium plating
Lb-in. galvanized
lb-in.
M2x0.4 10 6 0.125 0.070 4 5
M2.5x0.45 10 11 0.125 0.088 7 9
M3x0.5 10 19 0.125 0.106 11 15
M3.5x0.6 10 31 0.125 0.124 17 21
M4x0.7 10 46 0.207 0.142 22 30
M5x0.8 10 93 0.207 0.179 42 53
M6x1.0 10 157 0.250 0.2125 66 81
M8x1.25 10 380 0.315 0.2875 142 177
M10x1.5 10 770 0.394 0.362 248 310
最低样本数 8 4 4 4
7.7 self drilling screw
Dimensional ductility test
Minimum angle minimum torque
Strength lb-in. hydrogen embrittlement test steel plate (RB60-85)
0.002 "attack speed test plate
(RB60-85)
Gongsu 0.002 "
RPM axial load
Surface treatment note 1 tapping
time
Max, Sec
Imperial metric Style 2 style 3 A B C
4-24 M2.9x1.06 5 14 0.079 --- 0.062 2500 25 30 45 2.0
6-20 M3.5x1.27 5 24 0.090 0.110 0.062 2500 30 35 45 2.5
8-18 M4.2x1.41 5 42 0.098 0.142 0.062 2500 30 35 45 3.0
10-16 M4.8x1.59 5 61 0.110 0.173 0.062 2500 35 40 50 3.5
12-14 M5.5x1.81 5 92 0.142 0.209 0.062 1800 45 50 60 4.0
1/4-14 M6.3x2.12 5 150 0.173 0.209 0.062 1800 45 50 60 5.0
Note 1: surface treatment classification:
A: surface treatment thickness not exceeding 0.0003 (including): B: surface treatment thickness is more than 0.0003. C: chrome plated sample
2: sample nominal size #4 - #10, the use of 2500 rpm., #12 and 1/4, the proposed use of 1800 rpm., you can use 2500 rpm, but must be careful to avoid the high surface temperature generated by the impact of the test results
