V-block

A v-block, also known as a vee block, is a measurement block jig built to hold cylindrical parts in place during milling, drilling, cutting, adjusting, or inspecting processes. Made of either cast iron or steel, a v-block is designed with a v-shaped 90-degee groove positioned at a 45-degree rotation at the center of the tool. This v-shaped channel is used to stabilize and center a cylindrical part on which you are working. V-blocks are usually sold in matched pairs and come in a range of sizes.