Cuting tool geometry

[Bernard Laycock 1Participant @bernardlaycock1]

I spent some time today grinding the necessary rake and clearance angles on a new HSS toolbit and it occured to me that I have some carbide inserts that are all exactly the same in their geometry. The only angles that I can see are the front and side clearances but no top or side rake. Have the manufacturers of these inserts decided that the rakes are not necessary? My inserts are bought from one of the model engeneer suppliers and I wonder if more sophisticated insert profiles are available to the professional users. Or are the rake angles redundant?

bernard

[Bernard Laycock 1Participant @bernardlaycock1]

[KWILParticipant @kwil]

Which carbide inserts are you referring to?

[David LittlewoodParticipant @davidlittlewood51847]

The rakes on inserts is – if they have any – built into the edge. If you examine it closely you should be able to see it; many of the better ones have fairly complex chip-breaker shapes, but still with a positive rake. If they don't have any built-in rake, then you have got tips intended for work on cast iron, these are typically made with a flat top.

David

[mgjParticipant @mgj]

Not so sure – a lot of time time the rake can be built into the tool holder itself. No the rake angles are not redundant

I use negative rake tips a lot, and they are not designed for use in cast iron, though they are good in that, and excellent in copper and bronze/brass. Even better is the way they send the chips away from you!

Actually one can get tips with all sorts of rakes on them, though its true that the tips most suitable for the smaller lathe are positive rake. (though I have some excellent small Stellram non ISO boring bars in negative rake) However the CCMT tips are expensive because you only get 2 edges, (plus 2) for your money, whereas the negative rake W series give you 6.

For the amateur is it well worth using negative rake tips for parting off.

[Bernard Laycock 1Participant @bernardlaycock1]

The inserts I use are those marketted by Greenwood tools and in an effort to understand the geometry, I have asked them to provide this information (perhaps in the form of a drawing).

Bernard

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