Are lathe tool carbide inserts supposed to be sharp?

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awake

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Grinding steel on diamond disks can ruin the disks. Yes, diamonds are the hardest thing but when grinding steel the carbon in the hot diamonds can migrate to the steel and cause many problems which why you should only grind carbide on diamond wheels.
A very important word of warning. There is a caveat - as I understand it, at least one company sells a diamond grinding setup that 1) runs slowly enough not to build up a lot of heat, and 2) is water-cooled - and as a result they advertise it for use with steel or carbide.

*note that I'm going on the basis of fuzzy memory, so I may not have the details just right ...
 

timo_gross

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there is a CBN--Cubic Boric Nitride which is used as an abrasive second inhardness to diamond. But I haven't found any tool bits made of it yet.
CBN wheels can usually be bought from the same companies that also make diamond grinding wheels or other grinding wheels. :cool:
Not as difficult to find as they are difficult to pay for.... haha.
If you want to grind HSS CBN is the way to go.
 

SteveM

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Stefan Gotteswinter is a fine engineer who generally uses carbide for his lathe tooling and has produced some interesting videos on the subject. In one (link below) he regrinds carbide inserts, producing a sharp edge and demonstrating that the results in cutting steel, brass and aluminium are outstanding. In another he brazes used carbide endmills onto cold rolled steel for use on his small lathe.

Here's the one about the inserts: Regrinding Carbide Inserts
 

Nerd1000

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Sorry - - - need to look a little further.
Greenleaf Crop is one name that I remember for such tooling.
Used on hardened materials and really tough as used (IIRC for the second).
Didn't use them often but when you drop an insert made of CBN into the lathe and you're turning 4140 - - - - wow - - - feels like race car time!!!!!
(That was the demo in my training.)
You can pick up Chinese CBN tipped inserts on eBay. One insert will cost you the price of an entire box of carbide tips, but on the other hand it's possible to turn heat treated HSS with them.
 

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