1. Find the pitch to be machined in the table on the nameplate of the feed box, pull the handles of the feed box according to the position indicated in the table, and finally put the changeover handle in the "lead screw" position;
2. Before turning the external thread, the external diameter should be slightly smaller than the nominal diameter; The angle of the thread turning tool should be consistent with the tooth profile;
3. Find out whether it is metric thread or English thread, otherwise it will be confused and the threads behind the car will be inconsistent.
There are three methods for turning threads, namely, direct cutting, left-right cutting and oblique cutting.
(1) Straight-forward method: feed with the middle slide plate, and cut with two blades and the tip at the same time. This method has the advantages of simple operation, clear tooth profile and small tooth profile error, but the turning tool has large force, poor heat dissipation, difficult chip removal and easy wear of the tip. Suitable for machining threads with pitch less than 2mm and finishing high-precision threads.
(2) Left-right cutting method: The feature of left-right cutting method is that only one blade of turning tool participates in cutting, and at the same time, the small tool rest moves to the left and right for a short distance. After repeated cutting several times, when turning to the last 1 ~ 2 knife, the straight-forward method is still used to ensure the correct tooth profile and clear root. This method is suitable for machining large pitch threads.
(3) Oblique cutting method: Turn the small tool holder by an angle to make the turning tool feed in the direction parallel to the right side of the turned thread, so that the two cutting edges of the turning tool basically have only one cutting. This method has the advantages of small cutting force, good heat dissipation and chip removal conditions, large cutting consumption and high productivity. However, it is not easy to dig out the clear tooth profile, and the tooth profile error is large. Generally suitable for rough turning with larger pitch thread.