1. Add initialization instructions such as G90G54G96S 1500M03 at the beginning of the program.

2. Add G76 instruction at the position where thread needs to be processed, and set corresponding parameters, such as the starting point and ending point of thread, pitch, cutting depth and cutting speed.

3. At the end of the program, add M05M30 and other stop instructions to process internal threads with a diameter of 20mm and a pitch of1.5mm. Use the following G76 instruction, G76x20z-50p100q150r0.1f0.2, and X20 indicates the thread shaft and lathe center. P 100 represents the starting point of the thread, Q 150 represents the end point of the thread, R0. 1 represents the fillet radius of the tool, and F0.2 represents the cutting feed speed.