Multi-thread Turning

A thread with only one helical groove on the cylinder is called a single thread. A thread with two or more helical grooves is called a multi-thread thread. For each rotation of a multi-thread thread, the distance that the helix advances is called the lead, and the lead is equal to the product of the pitch and the number of threads.

The first problem to be solved in turning multi-thread threads is the method of splitting and the correct splitting. If the line splitting method is not selected properly, the line splitting operation will be incorrect, and the line splitting error will appear carelessly, resulting in different pitches of the multi-thread threads. It will seriously affect the screwing accuracy of the internal and external threads and reduce the service life. Therefore, attention must be paid to the selection of the splitting method of multi-thread threads, and attention must be paid to the correct operation of the splitting process during the turning process.

When turning multi-thread threads, pay attention to the following three issues:

1. The machine tool hanging wheel and machine tool adjustment should be determined and adjusted according to the lead. Never use the pitch to calculate and determine the position of the adjustment handle of the hanging wheel.

2. The lead of the multi-thread thread is generally relatively large, and special attention should be paid to the influence of the lead on the rear angle of the two cutting edges of the turning tool. The helix angle should be calculated according to the lead. When sharpening the tool, the clearance angle of the cutting edge on one side of the tool should be increased by one helix angle, and the clearance angle of the cutting edge on the other side can be reduced by one helix angle.

3. Thread fine turning should be finished together after rough turning of all spiral grooves. Otherwise, the consistency of each tooth shape cannot be guaranteed.