KP-3 and TT-4 best practices

[cncsnw]

The KP3 should have a lighter spring force than the TT4, so it should always trip itself on the TT4 without moving the TT4.

Theoretically, yes, there will be a consistent error in the measured KP3 probe height offset, relative to the measured offset of any other tool, because any other tool has to move farther Z-, by the pretravel of the TT4, before it is detected. That would make the control think that the probe is longer than it is; or that all the other tools are shorter than they are.

You can test this by measuring the probe, and measuring some tools, then using the probe to set Z0 on a gage block. Then call up some measured tools along with their offsets (e.g. "G43 H1", "G43 H2", etc.) and jog them down to the gage block. See how much farther down you have to jog them -- if at all -- to just touch the surface of the gage block. If you find the error is enough to matter, then write down that amount, and subtract it from the probe's height offset every time you measure the probe.

If you have a bed-type machine, you should not need to measure the probe's offset very often: only when you change the stylus, or change your mind about what surface you are going to set the TT4 on while you measure tools.