what steel for holders

[.RC.]

I have got myself a 75mm boring head but have no cutters for it and was going to make my own.

What is a good steel for making the holders for carbide inserts. I have easy access to get either 4140 or just plain black as drawn mild steel.

What are the best insert types for boring. negative or positive?????????

I have a few lathe insert tools I can copy the general idea off....

[pete913]

If I were going to make toolholders, I'd use 4140 because it's heat treatable. Its easy to machine too, although in this case, ease of machining is just a secondary issue. You want something that will do the job when you're finished, and I can't see an unhardened toolholder doing that for long. Use positive geometry inserts. Negative geometry inserts are for ridgid setups in powerfull machines, neither one of which is the case in a boring operation in a Bridgeport or similar mill.