this post was submitted on 25 Feb 2026
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Carbide is acceptable and will get the job done, but youre going to burn up a lot of inserts getting it dialed in.
Ceramic, on the other hand, is purpose designed for cutting hardened materials.
I was tearing my hair out trying to turn a hardened 4140 piece in my lathe even running carbide. Then I picked up some ceramic inserts and it was like night and day. Immediate and dramatic improvement in surface finish and tool life.
We have a face mill that takes the same style carbide (although smaller size) that my lathe tool does and I'm very interested to see how that runs with ceramic.
Tungsten and boron carbide should be much harder than any ceramic, though I have had similar experiences with carbide drill bits. I wonder what exactly "carbide" actually means sometimes.
Most carbide I've run into is usually around 65HRC. The ceramic is have in my lathe right now is 95HRC. Its a significant difference. Its brittle, so it doesn't like interrupted cuts, but it loves heat and speed that would cook carbide in seconds.
65 seems really low to me for something called carbide, but I'll need to do some research into this!