When it's time to replace the screws in a carbide insert holder, use the reference number on your holder to find the right size.

Pair carbide inserts with a holder to create end mills that reduce waste and cost in high-volume jobs. When the cutting edges dull, replace the inserts instead of the entire tool. These end mills are also known as indexable shoulder mills. All are noncenter cutting for operations where the sides of the teeth do most of the work, such as shoulder milling, contouring, and finishing. They can’t be used for plunge cuts. They have a square cut style for creating square slots, pockets, flat surfaces, and edges.

When choosing an end mill holder, consider the type of finish you want. The finer the finish, the more inserts you’ll need. More inserts mean tighter spacing, so you can machine at high speeds and remove material quickly while leaving a smooth surface. However, you’ll also need more machine power. Fewer inserts mean a coarser finish—the inserts are spaced apart to help with chip evacuation. A coarse finish is best for roughing applications, light machining, and cutting soft metals such as aluminum.