TIL most endmills have a shelf life printed on the box

I was organizing our tool cabinet last Tuesday and noticed these little date codes on some new 3/8" carbide endmills we got from the supplier. Turns out the coating breaks down after about 18 months even if you never use them. I checked the batch we had sitting in a drawer from 2021 and three of them chipped out within 5 minutes of cutting 6061 aluminum. Now I keep a marker to write the received date on each box before it gets put away. Has anyone else had coating failures on old stock?

3 comments

3 Comments

black.mark2mo agoMost Upvoted

Buddy of mine had a whole box of 1/4" coated roughers that looked fine but turned to garbage after sitting in his garage for two years. He said they cut like they were dull before they even touched metal.

patricia6342mo ago

Hang on, coated roughers shouldn't just go bad from sitting in a garage unless moisture got to them. If they were stored in a sealed box with any kind of humidity, the coating can trap moisture and cause micro-corrosion that ruins the edge. He probably had a batch that wasn't dry when packaged, not a problem with the tools themselves going bad over time.

dakota_murphy901mo ago

That really sucks about your buddy's roughers man. "Cut like they were dull before they even touched metal" is such a perfect way to describe it too, I've seen that exact thing happen with some old drills I inherited. Its frustrating when you think you've got a good set of tools stored away and then they just let you down when you actually need them. Makes you wonder if manufacturers are cutting corners on the coating process or something, cause you shouldn't have to baby tools in a sealed box.