Threading:
mould
The method of directly processing threads with dies.
rotate
The invention relates to a processing method for obtaining the plastic deformation of a threaded workpiece by forming a rolling die. Wire rolling is generally carried out on a wire rolling machine. The thread rolling machine is carried out on an automatic lathe with an automatic thread rolling head, which is suitable for mass production of external threads of standard fasteners and other threaded connectors. Generally, the outer diameter of the rolled thread is not more than 25mm, the length is not more than 100mm, the thread accuracy can reach Grade 2 (GB 197-63), and the diameter of the blank used is roughly equal to the middle diameter of the processed thread. Generally, the internal thread cannot be processed by rolling, but for soft workpieces (the maximum diameter can reach about 30 mm), the internal thread can be cold extruded by slotless extrusion tap, and the working principle is similar to tapping. The torque required for cold extrusion of internal thread is about 1 times that required for tapping, and the machining accuracy and surface quality are slightly higher than tapping.
The advantages of wire rolling are: the surface roughness is less than that of turning, milling and grinding; Due to cold working hardening, the strength and hardness of the rolled thread surface can be improved; High material utilization rate; The productivity is twice as high as that of cutting, and it is easy to realize automation; The rolling die has long service life. However, rolling thread requires that the hardness of workpiece material should not exceed HRC40；; It requires high dimensional accuracy of the blank; The precision and hardness of the rolling die are also high, and it is difficult to manufacture the die; Not suitable for asymmetrical thread of hobbing.
According to the different rolling dies, rolling threads can be divided into thread rolling and thread rolling.
Two thread-shaped wire rolling plates are arranged oppositely, and the staggered spacing is 1/2. The static plate is fixed, and the moving plate does reciprocating linear motion parallel to the static plate. When a workpiece is fed between two plates, the moving plate moves forward to rub and press the workpiece, so that its surface is plastically deformed into a thread.
There are three kinds of thread rolling: radial thread rolling, tangential thread rolling and head thread rolling.
Radial thread rolling: two (or three) thread rolling wheels are installed on parallel shafts, and the workpiece is placed on the bracket between the two wheels, and the two wheels rotate in the same direction and at the same speed, and one of them also makes radial feed movement. The workpiece is driven by the threaded roller to rotate, and the surface is radially extruded to form threads. For some lead screws with low precision requirements, a similar method can also be used for roll forming.
Tangential wire rolling: also known as planetary wire rolling, the wire rolling tool consists of 1 rotating center wire rolling wheel and 3 fixed arc wire plates. During wire rolling, the workpiece can be continuously fed, so the productivity is higher than that of wire rolling and radial wire rolling.
Thread rolling: it is carried out on an automatic lathe and is generally used to process short threads on workpieces. There are 3 ~ 4 wire rollers evenly distributed around the workpiece in the rolling head. During wire rolling, the workpiece rotates, and the rolling head feeds axially to roll the workpiece into threads.
Thread cutting:
Refers to the method of machining threads on workpieces with forming tools or grinding tools.
Thread milling: milling with disc milling cutter or comb milling cutter on thread milling machine. Disc milling cutter is mainly used for milling trapezoidal external thread on screw, worm and other workpieces. Comb milling cutter is used for milling internal and external common threads and tapered threads. Because it is milled by a multi-edge milling cutter, the length of its working part is longer than the length of the thread to be machined, so the workpiece can be machined only by rotating 1.25 ~ 1.5 revolutions, and the productivity is very high. The pitch accuracy of thread milling can generally reach 8 ~ 9 grades, and the surface roughness is R5 ~ 0.63 microns. This method is suitable for mass production of threaded workpieces with average precision or rough machining before grinding.
Today, with the development of science and technology, machining center has become an irreplaceable tool for all production enterprises, so more and more thread machining is completed by milling, which has high milling efficiency, simplified steps and high precision, thus bringing greater benefits to enterprises. In order to meet this demand, many companies came into being. Provide professional solutions for some threads with special needs.
Thread grinding: it is mainly used to process the precision thread of hardened workpiece on the thread grinding machine. According to the different cross-sectional shapes of grinding wheels, grinding can be divided into single-line grinding wheels and multi-line grinding wheels. Single-wire grinding wheel can achieve pitch accuracy of 5 ~ 6 and surface roughness of r 1.25 ~ 0.08 micron, which is convenient for grinding wheel dressing. This method is suitable for grinding precision screws, thread gauges, worms, small batches of threaded workpieces and shovel grinding precision hobs. Multi-line grinding wheel grinding is divided into longitudinal grinding method and cut-in grinding method. In the longitudinal grinding method, the width of the grinding wheel is smaller than the length of the ground thread, and the thread can be ground to the final size by moving the grinding wheel longitudinally for one or several strokes. The width of grinding wheel in plunge grinding method is greater than the length of grinding thread. When the grinding wheel cuts into the surface of the workpiece radially, the workpiece can be ground in about 65438 0.25 revolutions, with high productivity, but slightly lower accuracy, and the grinding wheel dressing is more complicated. The cut-in grinding method is suitable for large-scale shovel grinding of taps and grinding of some fastening threads.
Thread grinding: Nut-type or screw-type thread grinding tools made of soft materials such as cast iron are used to grind forward and backward the parts with pitch errors of the processed thread to improve the pitch accuracy. Hardened internal threads are usually ground to eliminate deformation and improve accuracy.
Tapping: Tapping is to screw a tap into a pre-drilled bottom hole on a workpiece with a certain torque to process internal threads. Turning thread is to cut the external thread on the rod (or tube) workpiece with a mold. The machining accuracy of tapping or tapping depends on the accuracy of tap or die. Although there are many ways to process internal and external threads, small-diameter internal threads can only be processed with taps. Tapping and tapping can be done by hand, or by lathe, drilling machine, tapping machine and tapping machine.
Thread turning:
Matters needing attention in thread turning: Considering the enlargement of thread profile, the major diameter (nominal diameter D) of external thread should be turned to be 0.2~0.4mm (about 0. 13P) smaller than the basic size, and the width of tooth tip after thread turning should be 0. 125 P(P is the pitch). When boring the bottom hole of internal thread, ensure that the diameter of the bottom hole is-p. In thread cutting, we should pay attention to setting enough acceleration feed section δ 1 and deceleration retract section δ2 at both ends to eliminate thread sections with non-standard pitch due to speed change at both ends. Similarly, in the process of thread cutting, the feed speed adjustment function and feed pause function are invalid; If the feed pause key is pressed at this time, the cutter will stop moving after machining the thread segment. The feed amount of thread machining can refer to the thread bottom diameter, that is, the final feed position of the thread cutter. The minor diameter of the thread is: major diameter-1.2 times the pitch; The feed speed of thread machining should be continuously reduced, and the specific feed speed should be selected according to the tool and workpiece material, but the last feed speed should not be less than 0.1mm. After thread machining is completed, we can judge the thread quality by observing the thread tooth shape and take timely measures. However, it should be noted that for external thread, when the thread crest is not sharp, increasing the cutting amount of the tool will increase the major diameter of the thread, which depends on the plasticity of the material. When the thread crest has been sharpened, increasing the cutting amount of the tool will reduce the main diameter proportionally. According to this feature, we should treat the cutting amount of thread correctly to prevent scrapping. For general standard thread, use thread ring gauge or plug gauge to measure. When measuring external thread, if the thread "over-end" ring gauge (general gauge) is just screwed in, but the "over-end" ring gauge (stop gauge) is not screwed in, it means that the processed thread meets the requirements, otherwise it is unqualified. When measuring the internal thread, use the thread plug gauge and measure it in the same way. In addition to thread ring gauge or plug gauge measurement, you can also use thread micrometer and other measuring tools to measure thread pitch diameter.
Thread bottom hole D drill =D-P, D thread diameter P pitch
Determine the purpose: when tapping the thread, it will not bite between the top and bottom of the thread due to extrusion (this phenomenon will also occur when tapping the thread with a tap) to ensure the effective working height.
Bottom hole depth h drilling =h effective+0.7d.
H effective depth of effective thread; Large diameter d thread
Judgment purpose: The main reason is that when tapping a thread with a tap without a hole, the cutting part of the tap has a cone angle, and the end can not cut out a complete tooth profile, so the drilling depth is greater than the effective depth of the thread.
M8 has coarse teeth and fine teeth.
1. For coarse tooth M8, the pitch P= 1.25, and the notation of coarse teeth: M8 (the pitch is omitted);
2. Fine tooth M8, pitch P= 1, fine tooth notation: M8x 1.
Thread seal:
It is impossible for any plane to be completely in close contact, so a leak-proof seal is needed. The traditional method is to use rubber, asbestos, metal and other gaskets, but it will leak quickly due to aging or corrosion. Using anaerobic adhesive instead of solid gasket can achieve close contact after curing, making the seal more durable. Maitrey super lubricant is a special inert material, which is widely used for sealing threaded pipe joints and plugs, sealing the mating surfaces of flanges, sealing the mating surfaces of mechanical boxes and so on. Good anti-leakage effect.
Super lubricants are mainly used to reduce metal-to-metal contact. As a thread sealant, the product forms a contact surface between the external thread and the internal thread to protect the joint from friction and wear, and can withstand the pressure of 1407 kg/cm2, even if the thread surface is worn, corroded or wrongly processed. This product is also an excellent gearbox additive, which can form a film on internal parts. So as to reduce friction, gear noise and leakage. It also significantly reduces the bending moment stress and meets the requirements of dynamic decompression. It can be used on the gasket surface or as a filler to prevent fluid from leaking through the seal. It can be used at the temperature of 3 16℃. This product can be used in stainless steel, aluminum, iron, barium, glass fiber and plastic buildings, and is not affected by acid, alkali or common solvents.
Instructions for use of thread seal: Apply Maitrey Blu‐Goo super seal lubricant to internal thread and external thread, and evenly apply it with a brush or other application tools.
Thread measurement:
1. For general standard threads, use thread ring gauge or plug gauge to measure.
2. Thread micrometer is used to measure thread pitch diameter. The method of measuring the pitch diameter of thread with a needle is called the three-needle method.
3. Tooth thickness vernier caliper is used to measure the pitch diameter tooth thickness of trapezoidal thread and worm.
4. Special measuring tools and instruments for measuring other parameters.