How do you know when the carbide insert is dull?

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Hartwell85

Hartwell85

Member
Joined
May 14, 2021
Messages
98
Location
Findlay, OH
I would like to know how other members determine when their carbide cutter is dull and time for rotation. Sometimes I think my cutter is dull but I am hesitant to rotate it to a new area because time in use has been very short. I heard that hours of use is one method but that can vary depending on the type and amount of materials being turned.
 
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Just a feel thing for me, after rotating all the way around, they are easily sharpened.
 
My experience sounds similar to Ken's. If I get some chatter during turning, I rotate the tool to a fresh edge. If the chatter is gone, it was likely the tool. If the chatter is still there, or if the tool seems to be cutting rough, I check the height of the tool rest, just to be sure I am cutting on center.

I save my used round cutters, and when I have 5 or 6 I break out the diamond grit sharpening cards, and sharpen the carbide cutters with Krud-Kutter as the sharpening fluid. I start with the fine grit, then finish with extra fine. It seems to restore the cutting edge pretty well.
 
A point to consider. Rotating to the next cutting edge is NOT an irreversible process. It takes about 2 minutes, going slow. So, if you get the urge... rotate that cutter! If it seems to make no difference, rotate it back. (Oh, boy: another two minutes expended.) You will get to know when it is time! It is important to mark the cutter in some way, so you know what you have used and what is still 'factory' sharp.

From my own experience, for pen turning: those carbide cutting surfaces really last a long, long time! For larger turnings, they will dull out a bit sooner, but still last a long time. It is all fun!šŸ˜Š
 
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