Matching an insert to a toolholder.

I took this picture today at work. Both of these inserts are negative rake and fit in the same holder pocket.
The one on the left has basically a positive edge grind, it is sharp and is excellent for non ferrous materials such as aluminum, brass and plastics .

The one on the right is for steel, stainless steel and other tough materials, it is negative rake and has a generous radius on the cutting edge, I am not talking nose radius but the actual intersection of the side and the top of the insert. Many will tell you that knife sharp tooling is the cats pajamas for lathe work surface finishes but this is not often true with carbide tooling.
If your machine will push such tools they will produce excellent finishes.
 
Thanks P. Waller,

I have used tools similar to the sharp one on the left and they work very well on my little hercus (equivalent to 9" southbend) giving me a very good finish even on hot rolled steel - I call it black bar = 1018 mild steel with foundry scale on it.

I use tools similar to the one on the right to break through the crust on cast iron, I dont think the little lathe is suited to this type of tool but it gets the crust off without knackering a sharp tool and then I can tidy the finish.

Bill
 
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