Thread processing is an important part of machining, involving dimensional accuracy, surface roughness, and feed paths during machining; for single- and multi-thread threading, their method of branching; Knife, etc.
. If you make a mistake, it will cause disordered teeth, the tooth type will be unqualified, and if there is a problem, there will be waste or affect the service life.
Difficulties encountered in thread processing
In the daily thread processing process, the triangular thread for turning small pitch is generally made of high-speed steel thread turning tool, which is processed at low speed, slow in speed and slow in efficiency. This is too slow for mass-produced parts. Can be calculated according to the formula, hard
The alloy tool is finished with medium and high speed 500r/min and three-knife processing.
(1) When machining thread, use hard alloy turning tool, can not carry out micro feed, surface roughness can not meet the requirements, how to solve?
High-speed steel turning tools are usually used for fine threading, especially for larger lead threads of finishing cars. This is mainly because high-speed steel has fine carbide grains and good sharpness, which can form sharp edges and cut during finishing. Small force, can use reasonable selection of cutting fluid
, low surface roughness. On the contrary, carbide cutters are less likely to form sharp edges when sharpened due to the coarser grain. Generally, in addition to high-speed turning small pitch threads, hard alloys are less used to finish the threads. However, the hardness and wear resistance of cemented carbide are
It is better than high-speed steel, and it can not use cutting fluid. If it can turn the thread with hard alloy, it will obviously bring certain economic benefits.
(2) Why should the hole diameter before turning the internal thread be equal to or smaller than the small diameter of the internal thread?
Because when the internal thread is turned, the diameter of the inner hole will be reduced due to the pressing action when the turning tool is cut (the plastic material is more obvious when turning), so the diameter of the workpiece before turning the internal thread should be slightly larger than the diameter of the internal thread, which cannot be equal to Or less than
The diameter of the internal thread. Otherwise, the machined internal thread diameter will be smaller than the standard size specified in the standard, and the thread surface quality will not meet the requirements. Moreover, since the actual small diameter after the internal thread processing is allowed to be equal to or slightly larger than the basic size of the internal thread diameter,
In order to facilitate calculation in actual production, the aperture size can be determined by the following approximate formula.
Turning the internal thread of plastic material D≈dP
Turning the internal thread of brittle material D≈d-1.05P
Where: d—nominal diameter of the thread (large diameter);
P—pitch.
(3) What is multi-line thread? What are the first problems to be solved and noticed when turning multi-thread threads?
A thread with only one spiral groove on the cylinder is called a single thread. A thread with two or more spiral grooves is called a multi-thread thread. Each revolution of a multi-thread thread, the distance the spiral advances is called the lead, and the lead is equal to the product of the pitch and the number of lines.
The first problem to be solved for turning multi-thread threads is the split method and the correct split. If the branching method is not properly selected, the branching operation is incorrect, and the branching error is sloppy, resulting in different pitches of the multi-thread threads. It will seriously affect
The screwing accuracy of the internal and external threads reduces the service life. Therefore, we must pay attention to the selection of the multi-line threading method, and pay attention to the correct operation of the branching process during the turning process.
When turning multi-thread threads, pay attention to the following three problems:
1 Machine tool hanging wheel and machine adjustment should be based on the lead to determine and adjust the handle position. Never use the pitch to calculate and determine the position of the adjustment handle of the hanging wheel.
2 multi-thread thread lead is generally large, pay special attention to the influence of the lead on the rear corner of the cutting edge of the turning tool. The helix angle should be calculated according to the lead. When sharpening the knife, the back angle of the cutting edge on the side of the knife should be increased by one helix angle, and the other side after the cutting edge.
The angle can be reduced by a helix angle.
3 Threaded fine cars should be finished together after all the spiral grooves are roughed. Otherwise, the consistency of each tooth type cannot be guaranteed.
(4) Why is there a mess when threading?
In general, the thread needs to be machined multiple times to be machined to the required profile and dimensional accuracy. In the first and subsequent passes, the turning tool tip is not in the spiral groove of the previous pass, but is left, right or on the top of the tooth. As a result, the toothed car is broken.
This phenomenon is called a mess.
The reasons for the disorder are:
1The pitch of the turning screw of the lathe is not an integral multiple of the pitch of the workpiece. When turning, the turning is not used for turning, but the turning and closing nut is used for turning. In this case, it is basically impossible to guarantee the spiral groove of the last pass in the previous pass.
Inside, it will inevitably lead to chaos.
2The pitch of the lathe is an integral multiple of the pitch of the workpiece. It can be turned by the lifting and closing nut. If the opening and closing nuts are not closed in the last pass, this will cause the workpiece and the turning tool to be misaligned, resulting in disordered teeth.
3 The gap between the nuts is too large and loose. During the turning process, the opening and closing nuts are automatically lifted up, which will also cause the workpiece and the turning tool to be misaligned, resulting in disordered teeth.
4 The axial clearance of the lead screw is too large, and axial turbulence occurs during turning.
5 During the machining process, the sharpening and changing of the tool did not re-calibrate the turning tool.
6 The workpiece is not clamped, and the workpiece rotates or moves axially in the chuck during machining; the turning tool is not fastened, and the turning tool moves in the axial direction during machining. These will change the original relative position of the turning tool and the workpiece, causing disorder.
(5) What should I do if there is a “knife†phenomenon when the rough trapezoidal thread or worm is used?Due to the large amount of roughing, in order to make the cutting light, the rough turning knife or the worm roughing tool generally grinds the radial rake angle. If the radial rake angle is too large, the clearance of the transverse feed screw nut is too large, and the phenomenon of "scissor" is likely to occur. To avoid roughing
The "knife", you need to pay attention to the following issues:
The radial rake angle of a threaded turning tool should not be too large, generally 3° to 5°.
2 Just feed the screw gap in the horizontal direction, and the hand feed is light and fast.
3 Do not use straight cutting method for turning. Because of the straight cutting method, the three cutting edges are cut at the same time, and the cutting force is very large, which is easy to cause “knivesâ€.
4 In some cases, in order to avoid the "knife", the negative rake angle can be used to turn the turning tool. This changes the direction of the radial force and achieves the purpose of preventing the "knife". This method of loading is guaranteed by appropriately adjusting the height of the knife.
The front face of the die still passes through the center of the workpiece, so it has little effect on the angular error of the tooth.
Keychain Light
Keychain Light,Rechargeable Keychain Light,Small Keychain Light,Button Keychain Light
Cangnan Younglite Electrical Co., Ltd. , https://www.younglitetec.com