I saw what 6 months with a dull endmill does to part quality and it's bad

4 comments

4 Comments

Respectfully, I think you might be overstating this a bit. Six months is a long time for a dull endmill, sure, but it depends a lot on what you're cutting and what the tolerances are. I've seen shops run dull tools way longer than that and the parts still pass inspection if the material is soft and the part isn't critical. Not saying it's good practice, just saying it's not always a disaster. If you're seeing bad quality, check your feeds and speeds first before blaming the tool life entirely. A dull endmill can still make decent parts if you slow down and compensate. Maybe I've just been lucky, but I've pulled worse off the machine and had it be fine after a deburr pass.

eva_thompson1mo ago

Remembered a time I ran a job on this old Bridgeport and the endmill was so dull it just burnished the surface but the part still passed.

olivia3981mo ago

I've been running a job on 304 stainless for the last four months with the same endmill and it still holds +/-.002 on a critical bore. If you're swapping tools every six months on aluminum or brass you're probably leaving money on the table. I'll grant you that feeds and speeds matter more than tool age most days, but a truly dull tool leaves a work hardened surface that screws up your next pass. I've seen guys replace tools that still had another 50 parts in them because they saw a tiny burr on the first part. That's just wasting carbide.

craig.mila1mo ago

I read an article a while back that said a lot of shops leave money on the table by swapping tools too early, exactly like @olivia398 is saying. That bit about work hardening from a dull tool is something I've seen happen firsthand on a friend's lathe. A tiny burr might not mean the tool is shot, but it can mess up your next pass if you don't catch it. I guess the trick is knowing when a burr is just from speed or from a truly worn edge.