There are three common shapes of triangular internal thread workpieces on pipe thread lathes: through holes, non-through holes and stepped holes. Among them, through hole internal threads are easy to process. When machining internal threads, due to the difference in the cutting method and the shape of the workpiece. The thread turning tool of the pipe thread lathe selected by NN is also different. The most commonly used internal thread turning tool in the factory.
1. Selection and clamping of internal thread turning tools
(1) Selection of internal thread turning tool The internal thread turning tool is selected according to its turning method and workpiece material and shape. Its size is limited by the diameter of the thread hole. Generally, the radial length of the tool head of the internal thread turning tool should be 3-5mm smaller than the diameter of the hole. Otherwise, the tooth crest will be damaged when the tool is retracted, and it cannot even be turned. Under the premise of chip removal, the diameter of the shank should be larger.
(2) The sharpening method of turning tool and clamping internal thread turning tool is basically the same as that of external thread turning tool, but when sharpening the sharp corner of the tool, special attention should be paid to its bisector must be perpendicular to the tool shank, otherwise the inside of the car must be vertical. When threading, there will be the phenomenon that the tool shank hits the inner hole of the workpiece, and the width of the tool tip should meet the requirements, generally o lp. When installing the tool, it is necessary to align the tool tip strictly according to the template, otherwise there will be a reverse tooth phenomenon after turning the pipe thread lathe. After the turning tool is installed, the saddle should be shaken in the inner hole to the end point to check whether there will be a collision.
2. Determination of the diameter of the inner thread of the triangle
When turning internal threads on a pipe thread lathe, drilling or reaming is first required. The size of the hole diameter can generally be calculated by the following formula:
When turning internal threads of plastic metals
When turning internal threads of brittle metals
In the formula, the nominal diameter of the thread (mm):
Thread pitch (mm).
3. Car through hole internal thread training
1) Before turning the internal thread, first turn the inner hole, plane and chamfer of the workpiece.
2) Drive an empty knife to practice feeding and retracting. The feeding and retracting directions of the internal thread are opposite to those of the external thread. When practicing, you need to make the marks for retracting and entering the knife on the scale circle of the middle skateboard.
3) The feed cutting method of the pipe thread lathe is the same as that of the external thread. When the pitch is less than 15 or the straight-forward method is used for cast iron threads, the left-right cutting method is used when the pitch is greater than 2mm. In order to improve the deformation of the shank under the cutting force, most of its cutting allowance should be cut off in the direction of the tailstock first, then the other side is turned, and finally the major diameter of the thread is cleaned. When the thread is inside the car, visual inspection is difficult. Generally, the left and right cutting method is performed according to the observation of chip removal, and the surface roughness of the thread is judged.
4. Pipe thread lathe with internal thread without through hole or stepped hole
1) When turning the undercut groove, its diameter should be larger than the major diameter of the thread, the width of the groove should be 2 to 3 pitches, and it should be cut flat with the step surface.
2) Optional turning tool.
3) According to the thread length plus 1/2 of the groove width, make a mark on the tool shank, which is used for retracting the tool and opening and closing the nut.
4) During turning, the retraction of the middle slide handle and the opening and closing of the nut (or reversing) should be fast, accurate and coordinated to ensure that the tool tip is retracted into the groove.
5) Selection of cutting amount and cutting fluid The selection of cutting amount and cutting fluid is the same as when turning triangular external thread.