spotting drill

For metalwork, this is countered by drilling a pilot hole with a spotting drill bit.

Center drills are made specifically for drilling lathe centers, but are often incorrectly used as spotting drills.

Spotting drills are available in a relatively small range of sizes, both metric and imperial, as their purpose is to provide a precise spot for guiding a standard twist drill.

However, the true purpose of a center drill bit is the latter task, while the former task is best done with a spotting drill bit (as explained in detail below).

The included angle of the spotting drill bit should be the same as, or greater than, the conventional drill bit so that the drill bit will then start without undue stress on the bit's corners, which would cause premature failure of the bit and a loss of hole quality.

Precision Tool Company, comprised of KEO Cutters, Richards Micro-Tool and Cutting Edge Technologies, produces a variety of specialty precision tools such as combined drills and countersinks, NC spotting drills, key seat cutters, end mills and countersinks.