中文版From tapping - fastener knowledge
Although self-tapping screws have been used for a long time, generally know how to make, but for the provisions of the standard specification and requirements, may not be very clear, in this only by the norms collected, sorted out a reading for everyone, so that How can a layer of self-tapping screws understanding. self-tapping screws in metal or nonmetallic materials pre-drilled holes in the self-tapping with the female thread of a kind of threaded fasteners. with high strength, single, single edge combination of features. Because of its self-forming or tapping out the match thread, so the combinations of high-locking capability, and can be loading and unloading. in Small screws on the size, thread type, head type, tapping drilling performance in engineering applications is almost There is no limit.
1 Development (Evolution): Since the beginning of 1914 the commercialization of self-tapping screws. The first followed the main design ─ ─ system is derived from the wood screw end can be carburized steel cone-A thread forming screws. At that time the main purposes is used in air conditioning systems bonding on the metal of the tube, it is also called metal screws. After 80 years of development, can be divided into four periods ─ thread forming, thread cutting, thread rolling and self-drilling.
Thread forming self-tapping screws (Thread Forming Tapping Screws) ─ system evolved directly from the metal screws, thread forming tapping screws used to be pre-drilled, and then drive the screw into the hole, force out with the female thread and the original position in the female thread of the material will be pushed to the male, between what we called the thread forming tapping screws. is only applicable to thin and has a plastic material, it is also developed; Thread Cutting Tapping Screws (Thread Cutting Tapping Screws) ─ cut the thread of the end of the cutting out of one or more channel mouth, to be able to pre-drilling screw, the use of screws and the toothed part of the tail in a similar way to the tap with the female thread cutting out. It can be used in thick, relatively hard or brittle materials such difficult shape.
Thread cutting screws (Thread Rolling Tapping Screws) ─ triangular teeth tapping screws, also known as Type TT (Type Tai are still patent) is based on the principles shaping the development from the tap, thread cutting screws have specially designed so that the screw thread and the end of the pressure in the intermittent roll into their own with the female thread. At the same time the material around the hole can be more easily fill the self-tapping screw thread and the teeth at the end of the space, because of its friction than Thread forming self-tapping screws for small, so you can use thicker material, the rotary torque required for better control, and the combined strength even higher. thread rolling screws than standard definition of the project from forming or cutting tapping screws in the material, heat treatment, a higher intensity and more clearly defined, making the self-tapping screw thread rolling into a real "structure of" fastener.
Drilling tapping screws (Self Drilling Tapping Screws) ─ also known as Tec, self-tapping screws in the assembly of all the process, the most costly is the pre-drill preparation. Self-tapping screws used, must be drilled. And also need to limit the aperture. without pre-drilling in some areas to save costs. This is the set of drilling, tapping, screw drilling operations in a self-tapping screws. drilling screws on the surface hardness and hardness of heart than the average self- tapping a little higher, because more drilling screws of a drilling operation, while still need to be drilling screws through the pilot, to test the screw can be drilled within the specified time and tapping the threads. The above four major Self-tapping screws to the design and development process, and another two for the special screw thread design, the first one is; the level of dental self-tapping screws (High - Low Tapping Screws) ─ used in plastic or other low-density material. Dual-thread design, high-thread (outer diameter of the larger teeth) even more acute with more level angle of 30 degrees screw thread type. Low thread (outer diameter of smaller teeth) has a thread angle of 60 degrees, only the high high teeth half of threads. a combination of high and low thread design reduces the rotation torque, pullout strength has improved, dramatically reducing the combined risk of rupture of the workpiece with the other dry wall in the construction industry (Drywall) The assembly purposes., with Such self-tapping screw thread design is particularly suitable for plastic, wood panels and parts.
The other is; double thread bugle head self-drilling self-tapping screws (Twin Lead Self Drilling Point Tapping Screws) ─ assembly can be easily screwed into dry wall, the steel teeth on the self-drilling and tapping the hole with the female thread . The speaker of the bear head with a concave surface can not undermine the fashionable spin to the wallpaper or plaster surface. Most of the self-tapping screws belong to commercial uses, such as self-tapping screws in combination screws (SEMS) offer, you can provide services more closely. And with the thickness of the screw thread, such as a special focus on the assembly line designers are after locking.
2 engineering standards: self-tapping screws of 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
3.1 Thread Type: Standard self-tapping screws identification characters, including representatives of thread and the tail shape of symbols. Self tapping screws on behalf of one or two characters to represent the mechanical screw thread or wide thread (SPACED). If the character with the identification "B" on behalf of the wide thread screw. no "B" are representative of the mechanical screw. end of the character used to distinguish between the representative for the self-tapping thread forming screws, cutting, rolling into or from the drill.
Machine screw thread with the Anglo-American unity as a 60 degree angle and coarse thread, fine thread, the same pitch, if lost or after the demolition of the screw if necessary, can be replaced by a standard threaded fasteners.
Wide thread screw with a 60 degree angle but the pitch is wide, and its wide-pitch, therefore, to the thread, so the steeper than the mechanical lead screw thread is great. There is the special thread used in plastics, The thread angle of 48 degrees, commonly known as PT Screws.
Thread forming self-tapping screws A, AB, B, BP, C and other types of thread rolling has been gradually replaced by self-tapping screws into, so they are not recommended for new designs. AB, B, BP differs only in the tail shape, AB has a threaded tail cone, B has a blunt end, BP has a non-threaded end of the cone, pointed tail center and begin to enter the pre-drilling thread forming. Thread cutting tapping screws have BF, BP, D, F, G and T and other forms, BF, BP is wide thread, and the remaining mechanical threads.
Identification of the different characters in its cutting end point. Each has a cutting end can be collected under the waste of shape cutting. If self-tapping screw screwed into the blind hole (not through the hole), then the debris will be left at the bottom of the hole and sealed . However, if the scoring through holes, the waste will be out the other side of the workpiece. Therefore, select the type of self-tapping screws must be considered and this, the waste may cause pollution, falling into the operation of the parts or the electronic substrate can not operation.
All thread rolling machine screws are threaded with coarse threads, like Anglo-American Unity, refer to SAE J81 requirements. Metric thread, please refer to the SAE J1237 and DIN7500 requirements.
Drilling tapping screws have cutting machine screw wide thread BSD and CSD are two types. There are other special thread types, including high and low double-threaded, while drilling a variety of attack is also applicable. Because of the nature of attack and thread the end drill, drill screws does not apply to blind hole operation. In the assembly of self-drilling screws, drilling completely through the workpiece to be carried out only after the cutting or thread forming, so often there will be some debris, and if they use the type of screw thread cutting, but inevitably there are broken crumbs. So on the practical need to consider this issue. there on the BSD and CSD drilling screws, see SAE J78 and DIN7504 (W threads) of the regulations.
Self-tapping screw thread is the most important outer diameter of teeth, and if too large, will lead to assembly of the torque increase, if too small, thread shear strength will decrease, and this feature can be easily determined by a points card or card rules measured out, in addition to this characteristic, self-tapping screw threads without any measurement, the reason is very clear, with the female thread is made of self-drilling tapping screws, you can tie their own, so without any co-ordination of the measurement, although the case, but still pay attention to manufacturing ANAI / ASME B18.6.4 requirements: C.D.F.G and T-: its own thread of a size not less than the minimum effective diameter of 2A, it can not be greater than the maximum tooth diameter. So sometimes customer requirements will be so. When required, due to restrictions on cutting groove, ring can not be successfully tested in the measurement of screw threads to be used on direct regulation. Another two self-tapping screw thread features worth mentioning is:
The self-tapping thread forming screw with threads is due to its extrusion, so the teeth bottom diameter of the screw must be slightly smaller than the pre-drilling in order to have space to accommodate the workpiece material to be squeezed out. And the shear strength will thread larger. the self-tapping screws thread cutting with the thread is cutting because of its shape, so the teeth bottom diameter of the screw must be equal to a little pre-drilling, while the smaller pre-torque, breaking strength and pullout strength is relatively low.
Self-tapping screw thread aperture diameter ratio of iron and testing
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 0.849 0.872 0.075 0.884 0.884
# 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 # 5-40 5-20 0.125 0.107 0.107 0.110 0.852 0.852 0.808 0.880 0.101
# 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 ... ... ... ... ... 0.842 0.177 0.149 ... ... ...
# 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 ... ... ... ... ... ... 0.932 0.905 0.177 0.172
# 12-11 # 12-14 # 12-24 0.216 0.188 0.188 0.868 0.868 0.921 0.199 ... ...
# 14-10 ... ... ... ... ... 0.895 0.242 0.217 ... ... ...
1/4-14 1/4-20 0.217 ... 0.250 ... ... 0.866 0.912 0.876 0.228 0.219
1/4-28 0.250 ... ... ... ... ... ... ... 0.936 ... 0.234
# 16-10 ... ... ... ... ... 0.888 0.268 0.238 ... ... ...
# 18-9 ... ... ... ... ... 0.888 0.294 0.261 ... ... ...
# 20-9 ... ... ... ... ... 0.906 0.320 0.290 ... ... ...
... 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 ... ... ... ... ... 0.924 0.372 0.344 ... ... ...
3/8-12 3/8-16 0.375 ... ... 0.328 ... 0.339 ... 0.875 ... 0.904
A few more teeth per inch, squeezing or cutting required for assembly of the more material. So the general mechanical screw thread to be greater than the width of the torque. But a few more teeth, the greater the shear strength after assembly, anti- Breaking out of thread and screw the better.
3.2 Type:
Fasteners made of one end of the shape of the part of the larger bearing surface formed. ANSI / ASME B18.6.4 provides for self-tapping screws 13 standard head shape. Please refer to the provisions of paragraph 1.2 B18.6.4. On the thread forming and thread in terms of cutting tapping screws, 13 in the 5 - flat countersunk (Flat Countersunk), oblate buried (Oval Countersunk), pan head (Pan), hexagonal, and hexagonal Chinese silk head (Hex and Hex washer Head) the most important, which accounted for five first-type self-tapping screws almost all above 90%, using self-tapping screws should first consider the five head type.
The other five other types of concave bearing surface for the flat (Flat Undercut), flattened entire edge (Flat Trim), oval concave bearing surface (Oval Undercut), oblate entire margin (Oval Trim) and the cylinder head (post hill Fillister ) is a relatively minor head type, and the mushroom head (Truss), round (Round) and 100 degree flat countersunk for the new design did not take, cover the function of the first type can be replaced by other, pan head can be replaced by mushroom and head, 82 degree flat countersunk countersunk flat 100 degrees can be replaced.
Thread rolling head tapping screws with the same type of selection, the main consideration for the use of flat-topped, flat dome, pan head, hex head and hex washer head five.
Drilling screws with flat top, flat dome, pan head, hex washer head, and the most common reason for not using hex head actual cause of the drilling process, the need to exert pressure on the tightening tool to support the drilling tools operation. Therefore, use the cross-topped, flat dome, pan head, or hex washer head.
Although the American National Standards only provides 13 standard head shape, but other commercial uses on the first type are still in use, such as dry wall screw head used by speakers, pizza and other head designed for use by the special head type, manufacturer Keyi Other information manufacturing.
Bearing Surface - Results pieces of support or positioning the part, often working through the bearing surface to the screw. There are two basic types of bearing surface, flat-bearing surface (a vertical rod with the end pieces) and the conical bearing surface (and the end pieces of shank formation point of view) the former in most cases to carry the load acting on the end pieces of the service force, which in addition extend the same level function type bearing surface, but also for positioning. with conical end pieces bearing surface is commonly referred to is countersunk head type. the first type of different applications, depending on the initial function of bearing surface and head torque transmission capabilities.
Flat bearing surface used bolts and bolt type
Flat Head: Round and mushrooms can replace the first new design of low head diameter, head circumference along the external characteristics of the high pick that edge, to play for high torque driving role in strength, with the first hole in the head type have minor differences.
Head: the head is the most common type of the past.
Top stigma: the standard flat round dome than the small diameter of the stigma, but because of the relationship between groove depth and thus relatively high, the smaller the diameter of the role of pressure in the small area can be closely combined in the surface of the flange and the increased . As the concentration of the set to ensure the drilling starts with the mold, they can be successfully used in the drilling hole.
Broadside dome head: for the first cut under the constraints and weakened the wire components for wear and tear, and therefore the most commonly used in electrical and radio cassette recorders, in order more fully in the down-type with its commitment to provide a more attractive face design type.
Large Round: also known as broad-brimmed oval head, is a low type, cleverly designed large diameter head shape. When the role of the combination of additional tolerance permitted, can be used to cover the larger diameter of the metal plate with holes. Also suggested flat instead.
Slotted head type: This is a creative type locking head, once the combination is not easy to lift, but it can start the general standard screwdriver. This simple design is usually the cost of the portfolio can solve problems and increase production volume, for the manufacturing process to create stunning economic interests.
Cheng hexagonal hole head: a wrench head with both high-end hexagon head type size pieces. Hexagonal holes of the mold completely from the anti-cold forming, head to the top there is a significant depression.
Hexagon Washer Head bearing point: If the standard hexagonal hole head bearing type, but in the basement with a washer head face protect the completion of the assembly, so as not to damage the wrench. Sometimes things look far more important role.
Hexagon head: This is a torque acting on the standard hexagon head type, there will be sharp corners trimmed to near tolerance characteristics. Can be recommended for general business use, also apply to a variety of standard models and various thread diameters. because it required a second procedure hexagonal bearing points than you.
Cheng Wotou: deep within the cylinder head bearing hexagonal hole, a common high-strength bearing Wotou Cap Screw. Deeper hole bearing torque acting on the high-end pieces.
Twelve: high cylinder head type twelve external points on the cloth, there lend a washer face under the load node pieces. Since the design of the torque to provide a high degree of convenience, so commonly used in high-intensity end pieces .
Plum head: a hexagon lobular type of medium height and with a washer type head bearing surface. Its design includes vertical side face and washers, torque bearing part surface in the lobes (lobules) transmission torque. This design the highest level of use of the external drive system, so that moment to play to the extreme. high torque transmission did not change the head itself.
Common cone bearing surface of the bolt and bolt type
Flat countersunk - Standard 80 ~ 82 degree angle, close to the surface to be bonded fasteners. Bearing surface area provides a good central.
Oblate hard at all - called "Oval Countersunk", which is similar to a standard flat head countersunk shape, but more widely used. In addition, a round, neat on the surface, the design is also more attractive.
Small flat countersunk - and the standard flat countersunk, oval countersunk, as Tau Kok is 80 ~ 82 degrees, but the first part of commitments to small 1 / 3, for the simple products, or very short length. Put it in detail, it countersunk holes for the standard and is very suitable for close co-pieces.
Countersunk flat (countersunk 100 °) - This special flat countersunk screws requires close coordination is gradually applied to the surface, it is proposed in order to break down on the soft material and less pressure on the larger point of the surface, especially for aluminum , soft plastic.
3.3 drive (Drive System):
Drive system, its function is to drive and the binding and transfer torque to loosen the fastener. In the whole system, torque fasteners is to make the full transfer has become the most important thing useful. Of threaded fasteners for There are two basic drive system, an external drive, an internal drive. external drive system is the driving factor in the whole head, wrench in the outside work. The internal drive system driven element is the head of the fastener Department, wrench in there operation. In general, the internal screw-driven in terms of allowing for higher torque.
The first type of external drive: Hexagon head, hexagon drive system, the first-second edge drive system.
Slotted is the oldest of a groove, drive systems for all this is the most common, cutting channel manufacturing in two ways: one is the complete type of screw head to cut a trench cutting machine repair ditch, and another is forming in the shape forging. forming a groove cut more economical, because it does not require secondary processing, but there are still problems in some areas, such as hex head or a hex washer head with direct molding, the Because depression (Indented) will cut it at the Goushen difficult to measure, more seriously, will reduce the screw with the screwdriver in the joints, direct molding used in the round, the joints the same, but the molding pressure will force the head diameter increases large, especially in the cut at both sides of the ditch, in some use of direct molding head type, head size very difficult to control.
Cut a groove for the type of depression, for all types except flat head and flat dome of the entire margin of the whole circle is outside the standard type, for each head type size requirements of the cutting channel in B18.6.4. Cut gully is especially suitable for hand combinations, but not suitable for semi-automatic or fully automatic assembly. The drive system of the effect depends on the height and flatness of the head, flat head and the Gang as the hills, it is because the larger head high, the deeper the cut groove, while the head The more smooth, drivers would be more close to the outer edge of the head, torque and more effective. If in practice, require a higher torque, shear is a problem. even deeper integration of driver and the driver Slotted between the hard to find a good match. The existing fastener in the drive and the gap between the cause is not vertical. When the drive is not perpendicular to the external force, slotted screwdriver will damage the shear caused by the edge of the head. The smaller or more rounded, more prone to this phenomenon.
Not slotted for quick installation, such as assembly-line, drive screwdriver slide from one end of slot the other side of the center if the driver drives the center of basic and fasteners aligned, the drive screwdriver effective. If there is no alignment, It will certainly lead to damage to the head, the same, drive screw screwdriver may also fall to the surface, directly on the fasteners, causing damage. With the increasing needs of torque, also called loaded to prevent shearing.
Slotted production does not exist, but in most cases, it really needs a second cut groove shape, the effectiveness of the current drive screwdriver and no problems. Slotted best for those who do not require high torque where especially those required in many different environments and adjust the loading and unloading, the best example is the adjustment screw on the carburetor. The same is also commonly used in such a groove perishable, the need to repair and demolition of the fasteners, such as : lawn mower, rotating equipment and so on.
In response to the extensive use of automated assembly and development of some depression, head type, it retains the high-torque, operating easy and fast assembly, while a considerable number of the first type of use is quite common, B18.6.4 recognized three types of them as the standard . are the cross points, respectively, type I cross (Philips), type IA m word (Pozidriv), type II (Frearson). Size requirements Please refer to 18.6.4. Type II was first developed, followed by type I, type IA, compared with the modified type I, type I and type IA which is most common, type II is less and less demand.
Cross recessed areas from cross slot hole, like a crossroads. Cruciform recess, the bottom edge of tilted cross on the middle slot, usually located in the center of the fastener head. It is relatively deep, can help drive screwdriver correction. Sometimes the groove depth has been the neck to reach fasteners, in this case, the ultimate strength fasteners are potentially weakened. It applies only to the torque from low to medium needs, because it's easy to slide out of the inevitable, which is the trough caused by the hypotenuse. Overall, 1.7 pounds per inch - 1 lb torque, will not cause slide, but more than this value the torque acting on the cross slot, it will lead to slide, a vicious cycle. Many Hou, this vicious cycle will make the fasteners completely lost the ability to work trough. This vicious cycle will cause the same loss of driving opener, in many cases will shorten the life of tools to increase the cost. cruciform recess have a good corrective, suitable for automatic assembly lines. productions without any problems, forming a shape in the head, do not do the second time processing. tool widely used. for manual and automatic assembly line of low torque requirements Occasion, for example: ultra-thin steel plate to the thin steel plate, thin steel plate to the cork, soft plastic.
FREARSON RECESS is another cross slot, commonly known as "reed & price" slot. (See 18.6.4 Type II requirements) and its design is very similar to the cross-slot, but the tank is a vertical edge and the bottom is pointed. Because These subtle differences, FREARSON have superior than the cross-slot drive performance, but also have some drawbacks, there will be slide-out phenomenon. This drive system can be used for low to medium torque requirements and drinking places, the more torque large, the greater the extent of damage trough and tools, the current production is no problem.
Because of this drive system applications is not very extensive, the limited supply of the appropriate drive, to be taken into account in the assessment of this. Slot can be used any place where the cross, FREARSON also be able to use some Occasion inappropriate cross slot, you can also use.
M word is a cross-shaped slot groove point, it is to overcome the shortcomings of the two trough developed on. The basic design is similar to the cross slot, but the extra groove, commonly known as "ribs." Suitable for low to and drinking places in the torque required, as opposed to the first two have greatly improved trough, can significantly reduce the probability of slide. m word also requires end-loading slot to prevent the slide, but can withstand higher torque will not hurt the tank and drive screwdriver. Because of its basic design similar to the cross-slot, the center also has a good degree, suitable for automatic assembly lines. m word molding process similar to the cross-slot slot, but also in the head forming a shape need for a second time processing. tools readily available, but to get the best results, use the m word slot of special tools, some people try to drive tools with cross slot, but the effect is not good. As word slot m the superiority of Those who can apply both the Occasion trough, it can be used. also can be used in the larger torque, such as heavy plate and sheet, thread cutting and thread forming machine, plastic material of the fasteners, and automatic low torque requirements on the machine screw.
Hexagon Socket drive system as the point of his name indicates, the head of the fastener has a hexagonal hole, often Socket head cap screws ", a high-strength fasteners. Hex hole for high torque Occasion . of this drive system, the slide is not a problem, but driving between the wrench and fastener combination of features, only used a few times, will be deformation points and wrench. In order to ensure the combination of the size of points and tools are there is a general tolerance, but this can only reduce the actual surface contact, and facility loss. This type of fastener higher prices, if those in need are often demolished Occasion, will greatly increase the cost. the production process does not big problem, as a shape. Before this, the hexagonal hole to go through two processes forming - drilling and punching. applicable tool called the "Allen wrench", are divided into two categories, short arm and long arm. hex wrench a hexagonal steel rod bent into L-shaped, for a fixed size, the proportion of the long arm wrench length is larger than the short arm wrench, its effectiveness is no problem. in the automatic assembly line, will also be driven with a hex screwdriver. hexagonal hole usually Occasion high torque, ideal for usage depends largely on whether the number of repeated use, for the frequent need to remove the fasteners, it is not economic, because the slot and tool deformation, increase the cost. hexagonal hole used for medium-sized equipment and heavy equipment for assembly of high strength fasteners.
Dentate hexagonal hole head (SPLINE RECESS) is essentially circular, in the Socket in the direction parallel with the fastener axis at right angles within the six ribs. Dentate hexagonal hole head of the application and the application of hexagonal hole is the same as the first , is used for high torque applications. It is designed to do is to make the hexagonal hole head and tools to minimize wear and tear. dentate hexagonal hole head of the main drawback is that hole in the head and tool manufacturing. point first because of its design complexity, must begin with when the fastener shape. Because of its many sharp angles, so extremely difficult to control production within the required tolerances. the production of the tools used to make points very short-lived head, it will generally increase the cost of fasteners. for the production of driven tools, there is also the same problem. because the supplier is limited, point-driven tools dentate hex drive tool than any of the foregoing is difficult to buy. dentate hexagonal hole head for high torque
Occasions, but often have supply problems make it difficult - especially when the demand. Elected to use the drive in short supply should be taken into account.
TORX RECESS (Plum Point head): Plum Point is Camcar designed the first patent. It is designed to solve all the above points the first drive system problems. Plum Point is a hexagonal head and blade design, with straight edges and lighter in the hole first. This torque transmission is designed to support, not like most of the surface of the head point-point support. Thus the efficiency can increase torque transmission. straight edge to eliminate reverse the trend and when the end of the sliding load. These Plum Point are the first in practice, has the best combination to pass the driving torque. In fact the first general Plum Point Point head than any other light, which means that the tightening force of the first hole depth will not produce losses. This has a very good design features make it the ideal tool for automatic assembly line. In manufacturing there is no problem. hole in the head is formed in the beginning with the process. As with many header plum point arc, not the right angle, manufacturing tool wear is also not significant. strict tolerances to ensure maximum binding.
Plum Point head a number of other patents can provide users with a variety of commercial sources. Tools available from many sources. Plum Point head of any torque application requirements, regardless of manual or automatic assembly are very applicable. It is designed to Elimination of sliding, so you can transfer more torque, longer life and create the first hole tool life. These advantages can reduce the cost of fasteners. Plum Point head can be used in high torque situations, especially re-use, such as heavy machinery and equipment. Plum Point head can be used for automatic assembly. This is because the deformation of the hole will not be the first rework tools have a long life, worker fatigue caused by operational errors and thus also reduced. in the application and automatically industry, Plum Point head is becoming more popular. Plum Point head for high-speed assembly of almost any occasion.
Hexagon: Hexagon is a common head style drive system and is widely used. It is used in a variety of torque requirements of the automatic assembly. It applies to middle and low torque applications. In high torque situations, with the hexagonal hole head The problem is the same. This will be deformed fastener head and the drive tool wear. because of the pressure caused by cracks in the sleeve for driving hex head often very short life span. This will greatly increase the cost of fasteners.
There are two types of hex head drive system. They make different. Hexagon socket head (INDENT HEX) is the head of an economic model. It starts with forming time together without the need for two processes. The entire margin of hex head (TRIMMED HEX) is a more expensive one. Heading, then the second processing procedures hexagonal surface. This makes the angle more acute, favorable performance and looks good. In addition, two types of head will sometimes slotted hex head, This can also be used when necessary screwdriver driven.
Very popular driving tool. Hex for manual and automatic assembly, the use of low-torque applications. Rated torque to remember. Fastener driving tool when the deformation, the rest of the system should be reexamined. Outside the hexagonal head plate assembly in a variety of firmware is very useful.
Second edge head: second edge drive system is mainly used for high strength-givers wrench system aircraft industry. Second edge design is based on cylindrical with a moderate peak - as name implies - twelve edges. When the time for the aircraft industry will be drilled along the center of the head to head height of 2 / 3 of the weight reduction of high fine. second edge is mainly used for high-strength fasteners. The fasteners used in high torque applications. The head of the driver is sleeve with the same structure. second edge systems are generally better than the hexagonal system, but the drawback is the same. fastener driver with mainly in the edge, not the surface. When repeated use, easy to wear into a round edge Fixed shape leaving turn fasteners. drive sleeve and a disadvantage. because the structure is exposed fasteners torque reaction caused by cracking in the wall socket. This fastener itself is very expensive, the disadvantage also increased its costs. second wing structure manufacturing than many other types of structures is difficult, but it is also beginning with the shaping. generally get driving tool.-second commercial on the edge drive system for high intensity applications. especially for COUNTERBORE occasions, heavy machinery and equipment and aircraft.
Outside the plum head: Plum drive system for all occasions outside the wrench driver. Plum-type-driven design is the hexagonal lobes are parallel to the fastener axis straight edge, highly affordable. Lobulated surface contact when the drive rather than most other drive system for the point of contact. which makes more efficient torque transmission. plum can be used for any external drive system torque requirements, but it is the most suitable and high, medium torque applications. It's fast, easy and drive automatic and combination tools It is very suitable for automatic assembly outside the plum-type head outside the same type as the other driver with a sleeve. because it is effective transmission of torque with the supporting surface, the sleeve is essentially not damaged, thus saving the cost of driving tool, and thus greatly reduce high-speed, a large number of applications of fasteners costs. fastener head will never be reused even if the deformation. This saves the cost of fasteners in the assembly, service and return to work. plum blossom design in head shape easily in tight tolerance, all Manufacturing is also no problem. tools are also available from the high profile of several large suppliers to buy. The first type is to solve the problem, including automatic assembly tools for damage and deformation method fasteners. plum drivers for the manual or automated assembly Most situations requiring high torque. plum head suitable for assembly, automotive, heavy machinery and equipment. plum head is perfect for thread cutting and thread forming tapping screws. when extra torque is necessary occasions. plum first use are many and varied.
3.4 Screw Length: screw in the assembly to ensure full thickness pieces of thread and tie combination, the screw length is important. The average screw length should be equal to the combined length (total thickness of the component) plus the screw end. Screw end for the incomplete thread part of the thread forming screws combined with AB or BP-type cone tail length or tail length auger drilling. These different cone length of tail, or drilling are provisions of the specification, and B18.6.4 has its formula in Appendix .
For example, we want to use 1 / 4 "-20 pan head thread forming tapping screw to assemble a 0.25" thick and a 0.21 "thick plate, the maximum length of the screw end of 0.175", screw length tolerance is +0 -0.03. " the screw length should be 0.25 +0.21 +0.175 +0.03 = 0.665. "Therefore, you should use 3 / 4" length of the screw. At this point, after exposure to the other side with the length of 0.75-0.21-0.25 = 0.290 ", tapping screws generally suitable for 1 / 8 "length increased.
4 materials, heat treatment, final disposal and mechanical performance requirements: self-tapping screws can be carbon steel, stainless steel, copper or aluminum. And steel accounted for from the tapping vast majority, even more than 95% of iron and steel material from outside tapping screws tight book in JIS B1055 2 subsidiary mechanical properties (hardness and torsional strength) of the regulations, the rest no national norms or other recognized specifications, mechanical properties are generally for buyers and manufacturers to agreement. This article discussed The problem, almost concentrated in the carbon steel materials.
4.1 Material: Carbon steel self-tapping screws are made from low carbon steel, when customers request, are also used in the steel maker. But most use the C1018 - C1022 Material (This is because the carbon content to 0.15 % of the heat treatment on the work). materials largely by drawing wire annealing or spheroidization → → fine lines, stretch forming process to meet its conditions. provides material composition is as follows:
English 1 material chemical composition of self-tapping screws
Analysis of two self-tapping screws component specifications limit the percentage of% by weight
Carbon-manganese
# 4 or smaller furnace of 0.13 - 0.25 0.60 - 1.65
Check products 0.11 - 0.27 0.57 - 1.71
# 5 to 1 / 2 inch furnace of 0.15 - 0.25 0.70 - 1.65
Check products 0.13 - 0.27 0.64 - 1.71
1. Metric screws no special requirements and restrictions of their chemical composition.
2. Furnace analysis is used to provide order information. Products, check the screws to consider the heart of the Department of carbide segregation.
4.2 Heat treatment: self-tapping screws required by carburizing the surface is very hard to get for scoring forming or thread cutting. Carburizing and quenching and tempering heat treatment, the specification requirements on the mechanical properties are:
Surface hardness: general self-tapping screws should be carburized surface hardness above 45 HRC in order to iron in the scoring. Drilling screws in the surface hardness and hardness of heart than the average self-tapping screws a little higher (J78 required surface hardness shall be 50 ~ 56HRC), this is because drilling screws drilling of more than a job. In order to achieve the daily test or a quick check of the purposes, the surface hardness can use HR 15N, Knoop's micro hardness test, or micrograms. the choice of these methods
