What category of broaches is used to remove material from internal surfaces?

The correct choice is the internal broach, as this type of broach is specifically designed for creating or enlarging holes and shapes on the internal surfaces of a workpiece. Internal broaches excel in cutting materials from within cylindrical or irregular shapes, making them ideal for applications like honing or finishing internal diameters, keyways, or other profiles.

These tools typically feature a series of progressively larger cutting teeth; as the broach is pulled through or pushed into the workpiece, material is removed, allowing for precise shaping and sizing of the internal feature. The unique design of internal broaches allows them to effectively engage with the material, ensuring that the cutting action occurs within the confines of the hole or cavity, which is essential for achieving the desired final dimensions and surface finish.

In contrast, external broaches are designed for operations on the external surfaces of parts, which does not apply to this question. Flat broaches are a type of external broach that specifically shapes flat surfaces, while coated broaches refer to the application of coatings on the tool's cutting surfaces to enhance durability and reduce friction, which is not related to the category of broaches used for internal material removal.