Do you know how to tell a plunge bit from a non-plunge bit?
A non plunge bit has cutters around the periphery, but not the center. It can enter grooves from the side and cut moving sideways.
A plunge bit has cutters that go all the way to the center of the bit face. It can cut moving vertically as well as sideways.
Above see the bar across the center as well as the two edge cutters? Without this bar, when you drive the...