Entry of a threading tool into material can be programmed in more than one way. One of the most important selections is a method that controls threading tool approach towards the thread, also known as threading infeed. This is a method detailing threading tool motions, using one of two basic methods of infeed, as illustrated in Figure 38-14.

Figure 38-14: Radial and compound infeed for thread cutting

The simplest infeed method in thread programming is called the radial infeed method, also known as the plunge, straight, or perpendicular method. More common method is called an angular method, better known as a compound infeed or a flank infeed.

A need to control infeed direction in threading is to offer the best cutting conditions for cutting tool edge. Except for threads with very fine leads and some soft materials, the majority of threading cuts will benefit from a compound infeed (at an angle). Some threaded shapes are excluded for the reason of their geometry - for example, a square thread will always need a radial infeed (straight plunge infeed). The angle of infeed is programmed as the included tool tip angle in both types of G76 cycle.

Each infeed method has its variations, using the following features for one purpose - the best chipload control:

• Constant cutting amount

• Constant cutting depth

• One edge cutting

• Both edges cutting

There is a lesser known setting P in the one-block G76 cycle that selects...