Tool length offsets seem fine but I still get Z drift between tools

[TovalRandonneur]

I’m a bit nervous posting this because I feel like I’m missing something basic, but I’m getting Z drift between tools on a simple multi tool job. Each tool looks fine when I set it, but after a tool change the Z ends up slightly off and it shows up as a step or a depth mismatch. It’s not huge, but it’s enough that parts don’t look consistent and it makes me second guess every tool change.

A specific example was this week on a small part where tool one cut the pocket depth great, then tool two came in and it was just a little different like it gained or lost a few thou. It was satisfying that the program ran clean, but the Z inconsistency is killing my confidence. Where would you start troubleshooting, tool setter repeatability, toolholder seating and chips on the taper, thermal growth, or something in the controller offset handling that a beginner might overlook?

 

[BlackWorkshop]

If you can, run a quick sanity test. Measure tool 1, then measure tool 1 again without cutting anything. Same for tool 2. If it doesn’t repeat, it’s probably tool setter or tool clamp consistency, not the program.

 

[Alan]

I’d start with the boring mechanical stuff first. Clean taper and holder, check for a single chip on the spindle face, and make sure every tool is seated the same way every time. Then verify you’re calling the correct length offset per tool at every tool change and not accidentally reusing an H value.