What the tool bit does is actual material removal, and it will be held in the tool holder then attached to the tool post.
1.The most common type of metal lathe tool bits that you can see in the home and hobbyist shop is the high-speed steel cutting tool. It’s easy to work with and a good fit for benchtop machines. They are going to be smaller and have lower horsepower, you need to grind the high-speed steel into the shape required for the type of cutting operation to be performed. High-speed steel is also good for interrupted cuts, it’s a little more flexible than other types of tool bits, if you are turning down a hex bar or dealing with key slots, it’s an ideal choice.
2.The second type of tool bit is carbide insert tooling, which you can see in lots of professional shops and big machines, it’s good for production because the insert can be rotated, it’s difficult to use at home because it has minimum speeds and feeds to get good results, your machine has to have high horsepower and high rigidity for production. Compared to high-speed steel, the carbide inserts are more expensive.
3.The third option is called brazed carbide, it’s literally a random chunk of carbide that’s been braised onto a shank, it’s useful if you need to cut something very tough, carbide is extremely tough but it’s also brittle, so it’s not as good for interrupted cuts. The high-tech profiles cut into the tops of them are chip breakers.
4.The last type of metal lathe tools are the cut-off blades or parting blades, it’s a carbide insert type which has a little replaceable part. High-speed steel cutoff blade also suitable for home machines with less horsepower and less rigidity.
You can change the angle of the tool post with a wrench, this allows you to get the angle of the tool bit relative to the material, to get the right clearance angles for your cutting.