Compound (flank) infeed does not present programming problems when using the advanced G76 threading cycle. If a CNC system has G76 cycle available, it can be used for about 95% of all work. What about the remaining 5%? What if G76 cycle cannot be used and a program needs fully controlled compound infeed? How to control other infeed methods available for G76, without having the G76 cycle available or finding it impractical to use?

Unfortunately, there is only one way - take a pocket calculator and calculate each and every tool position and tool motion individually. Is it a lot of work? Yes. Is it worth doing? Absolutely. It has to be a really good job from the start, because even a slight modification at the machine could be very difficult. Atop class programming job is always worth the extra time and effort when quality and precision of the final part depend on it. Quality is not instant - programmers (and machine operators) have to invest some extra work and time into it.

General principles of compound threading as applied to a block-by-block programming are simple, but the programming work may be tedious and editing on the machine may be impractical. Each threading pass has to be calculated in a different Z-axis start position. This is called the shifted position that must be calculated exactly, otherwise the program will fail. It also had better be right the first time, otherwise any changes could be long and...