BASIC THREADING CYCLE - G92

BASIC THREADING CYCLE - G92

Computerized control systems can perform many internal calculations and store their results in control memory for further use. This feature is especially useful for thread cutting, since multiple repetitions of block-by-block tool motions can be avoided and the program shortened quite significantly.

For better comparison and to illustrate a simple threading cycle, the same threading example that illustrated previous G32 command will be used again (12 TPI on a 3.000 inch external diameter), providing identical results. This cycle is usually called the G92 threading cycle on Fanuc or similar controls, also known as box threading cycle.

A word about another G92 command. Some programmers may be used to registering a current tool position with G92 command for milling applications. On CNC lathes, a command for the same purpose is G50, not G92. G92 used for threading has nothing to do with now virtually obsolete position register setting command. This applies for older control systems only - modern controls use advanced geometry offsets. Format for the G92 threading cycle is:

G92 X ? Z ? F ?

where

Schematic illustration of G92 straight thread cutting cycle is shown in Figure 38-11.

Figure 38-11: G92 - Simple thread cutting cycle, also called 'box threading cycle'

The program will do exactly the same job as with G32, except it will have a noticeably different structure.