Carbide inserts

Sep 24, 2005 4 Replies

Got some carbide inserts off eBay, nice and cheap, for playing about with. The main reason I got them was to use in a flycutter that I'm making (a T-shaped one like the Japanese guy with the web site made). They're triangular with a hole in the middle. I notice that there's no relief - if they were mounted on a lathe tool, set horizontally, the face/edge towards the workpiece would be vertical rather than sloping away a bit. Are these intended to be used on a lathe, or are they for something else?



Having received them, and looking at the selection of broken lathe tools I inherited from a mate, it ocurred to me that I could braze an insert onto one and make a long-lasting tool. Can these carbide thingies be ground to a suitable shape and still work?



In message , Wally writes

They should be held with negative rake, i.e. tilted forward to provide clearance.

Yes, but you will need a 'green grit' wheel or diamond stone, and 'suitable shape' may not be the same as with high speed steel.

So that the top face is tilting down towards the workpiece? Won't that prevent it from 'digging in', if you see what I mean?

I tried with a carborundum stone for a while last night - didn't make much difference, but the stone was spinning fairly slowly.

Yes

No

It won't - not hard enough. You need a silicon carbide abrasive, not aluminium oxide.

I thought carborundum was silicon carbide...

Regards, Tony

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