A chamfer is a beveled edge that joins two surfaces. The tool used to measure a chamfer would be a caliper.

of Chamfer

A chamfer 'breaks' a sharp edge.

eg. after drilling a hole, it is normal practice, especially after drilling in metal to chamfer the edge.

eg. chamfers can be made to the edges of prepared wood to prevent the edge breaking away, or causing splinters.

Generally the most common form of chamfer is one of 45º

how do you use a chamfering cutter

If you are asking "What is a chamfer washer?" ?? These are used for bolting together sections of RSJ which have a tapered profile on the inner faces. consequently the bolts pull up "square".