Turning with Round Inserts

It does. You just need a pretty solid setup so the tool doesn't skate. It applies a lot of pressure to the workpiece.

I had a few samples I got from Valenite, I think, in micrograin carbide amd with a sharp edge. I could cut mild steel with them on my old SB lathe. But most round inserts aren't so free-cutting.

I ground some half-round HSS bits to cut wire rope grooves in aluminum and stainless pulley sheaves, which I made narrower and larger in diameter than commercial pulleys for fiber rope. They do leave a smooth finish but I had to wiggle them back and forth to reduce the chip width instead of plunging straight in, or they would chatter excessively on my old SB.

-jsw

While my Harrison M300 will take a fair cut and the largest radius bit I have is 8mm radius these days when I make the likes of bending formers for my rotary draw tube bender I use the rotary table on the BP as it is far easier and less prone to issues.

Adding to that, round inserts are usually made either for milling or for rough-turning with rigid machines and a lot of horsepower. But you get a "wiping" effect because of the geometry, and some applications allow them to be used as really aggressive (and very strong) roughers, while producing an adequate finish for many applications at the same time, in a single pass.

Watch for chatter. As Jim mentioned, that's a limiting factor. Chip-breaking is another.

BTW, for single-pass turning with rigid lathes, wiper inserts are the coolest thing going. Or they were, a few years ago, when I last wrote about them. I watched them at work at Sandvik (in NJ), and they were fantastic.