What type of carbide inserts or is HSS better for threading and turning barrel contours on stainless barrels.

The best for turning barrels and threading are carbide inserts. You have to take it easy with the carbide tips because they can chip easy but they last so much longer than high speed. They work well with all types of steels and cut smooth. Stainless barrels turn very nicely. Hope this helps.

McD---

Carbide insert tooling is the least trouble and the best consistent finish but you must have a solid machine to use them well.

Positive rake tools take less horsepower to run and will give a smoother finish at normal shop speeds and feeds than negative rake tools.

I'd probably go with HSS for threading, as it is more flexible than inserts. For instance you can flip an HSS tool upside down, run the lathe in reverse, and thread from the relief cut in the workpiece out. No more worring about running into a shoulder... Also, I like my lathe turning slow rpms when threading, and in general, carbide is a lot happier when the surface speeds are higher. This might be the difference between threading at 65 rpm versus 400 rpm...

For general turning, facing, and simple contouring, I'd recommend an 80 degree diamond insert negative rake tool holder, and then use what is called a negative-positive insert. By using a negative holder, you get twice the number of cutting edges as you would if you were using positive rake holders. But, there is a positive rake built into the insert so you get lower cutting forces.

Realize that there is a whole science for insert selection as well. Different materials work better with different substrates, and different coatings, and different geometrys. By going to a diamond with a smaller included angle, you get a more flexible tool. As in it is both not as rigid, but can also be used for more complex contouring.

You can use carbide tooling on some small lathes. My South Bend is certainly no monster, and the use of carbide has not been an issue. For roughing, I keep the rpms up and the feed rates and depths of cuts moderate. I also had to mill an eighth of an inch off of the top of a 3/4" shank tool in order to use it in my tool holder, but that way I could use the common sized inserts rather than the more expensive smaller ones.

Check with your local tool supplier on which manufacturer is having some sort of introductory special. Tooling manufacturers make their money on selling inserts, not on the holders, so they're always trying to get new customers hooked on new products. A holder and inserts may go for as low as $100 on special. 10 inserts may literally last for years when used for gunsmithing.

Scott (Not really a gunsmith, but back in the day I spent 12 years doing CNC operation and programming)

[ 06-16-2003, 12:22: Message edited by: Scott Thornley ]

Positive rake tools take less horsepower to run and will give a smoother finish at normal shop speeds and feeds than negative rake tools.

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I think it is a good thing in breasts also. Positive rake is much more enjoyable than the negative ones.