Can carbide end mills become more brittle during OD grinding if no coolant is used?
We are having to modify a 1/8" 4-flute, carbide end mill to cut a hidden relief in a 17-4 cylindrical part. The shop supervisor mentioned that he has seen heat buildup during a regrind operation cause embrittlement in the cutter. If this is the case how does this cause embrittlement and how do I anneal carbide after the grind. I am doing this on a manual surface grinder with a powered spindex & diamond wheel, and no coolant is possible on the machine.
@W_ScottStark
I’m not sure what the answer to your question and is.
We always used coolant when grinding down the shank of in Mills for relief. It helped keep them cool. I did it on an old Cincinnati tool grinder with spray mist. This also help capture the Dust!
I am old school and have always been told that if carbide gets too hot it will create micro-cracks (fractures) causing it to break down (dull) faster. I was also told that carbide doesn’t follow the grain structure of the wheel as softer metals do. the material crumbles as the wheel strikes the surface. I hope this makes sense and if it isn’t true any longer please let me know.
UPDATE: So, we were using a relieved, four flute 1/8" end mill with full length engagement on the face of the part. I suspect that the four flute had some chatter and was why it broke prematurely. I have attached a pic of the six flute end mill that we went to and have now machined 70 parts with it. Because we have ran so many parts with the six I am starting to believe that it was not heat induced afterall. Your thoughts?
There are so many possibilities for failure. Glad you have a working sultion.
It still doesn’t hurt to try the spary coolant. You can even try a hand squeeze descending jug. Part of the spray mist also keeps the carbide desk down that stuff is really bad juju on the body!
If you use that tool or the job is repeat work I recommend you ask your tool supplier to make you some.
Thanks Rump’! I did use a cold air gun on the remaining grinds but it did blow the carbide around a bit. We produce medical instruments so contact materials must meet FDA requirements. Have you tried using Isopropyl Alcohol to help cool things down? I know methanol is also a probability.
