Re: end mill life question
Lots of air and no coolant for carbide. Micro-chipping of cutter with the coolant causing thermal shock as stated by Farmers Machine.
As much energy removed by the chips as possible. Blue-black chips are fine, and they always hurt!!
3 flute cutters, I have found work well in slots, because the 'back side' can't react against the front. 3 flute cutters are a bit stiffer, too.
Always climb mill.
Working in slots is always a problem because climb milling is next to impossible when contact is more than 30-40% of the diameter.
Multiple passes in a slot with a smaller cutter might be a solution, but your depth of cut will be reduced and number of passes takes much longer.
Reduced feed as cutter starts into a cut, from an edge, can help.
Doing a lot of work on SS316L (low carbon) my initial cutter life went from 20 minutes, moving towards 4 hours with experience.
I discovered that once a tooth had dulled, making it work harder, to even up the wear on the other teeth, made the cutter come back to life!!
I found as soon as it was starting to turn pear shaped, I upped the feed by 20% until it settled again, then became less aggressive.
I discovered this at the end of a BIG production run while stretching the life of the last few cutters. <<'cutters' link (if you got the link) to advert NOT BY ME. What dumb sh1t is this??.!! What is VigLink?? Grr!!!
This did eventually, after some delay, fix it!! Opt Out of VigLink
Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. Three ways to fix things: The right way, the other way, and maybe your way, which is possibly a faster wrong way.