Got told I was programming my tool offsets all wrong - old timer vs new training

So I had this inspector come through last week on a big job we were doing for a medical parts company. He watched me set up a new endmill and asked why I was touching off with the tool setter at a different Z than the actual part surface. I said that's how I learned at the trade school up in Dayton, you use the table as a reference and then add your offset from there. He said no, that's gonna give you trouble with thermal growth on longer runs. He showed me his way where you touch off at the actual work surface height. I been doing this for 4 years the other way and never had issues. But he's got 25 years experience and does audits for a living. So which way do most of you guys do it? Touch off at table height or at the part surface? Is this just a preference thing or am I actually messing up my tolerances? Got a big run of 316 stainless coming up next month and don't want to scrap parts.

3 comments

3 Comments

barbaradavis2d ago

Table height guy here too. Thermal growth hasn't been an issue yet though, has it?

kim_mason552d ago

Honestly, I used to touch off at the table too but that inspector's thermal growth point made me switch.

laura_wilson2d agoMost Upvoted

That 45 degree thermal growth number the inspector threw out there is real in certain setups, Barb's machine might not see it yet but it catches up. I've seen enough temp swings in aluminum work to know touching off at the table can bite you later on. @barbaradavis you might get away with it now but give it a few hot summers and see if that tolerance holds.