Drilling and Tapping

Description
Tapping is the process of creating threads on the inner surface of a drilled hole. A variety of taps are available in the shop to match almost any screw type available, including metric and standard measurements. Information required to select the drill bit includes thread count, diameter, thread pitch, and coarse/fine threads.

Using Oil
Oil is a necessity while drilling and tapping. It prevents overheating, helps clean out the chips created by the bits, assists the cutting action, and prevents the bits from squealing.

Center Drills
Creating a drilled and tapped hole first requires using a center drill. This gives the larger bits a center to align to, since most drill bits aren't perfectly centered when mounted in a drill chuck. This ensures the larger bits will drill in exactly the right place and won't walk across the part.

Pecking
While either drilling or tapping, pecking helps ensure the bits won't overheat or break. Pecking is the process of drilling into the part a way, then backing out to remove the chips and allow the part to cool. Common practice is to rotate the handle being used about a full turn, then back a half turn. Every time the bit/tap is pulled out, as many chips as possible should be removed and oil should be added to the surface and the bit/tap.

Alternative Tapping Methods
There are alternative ways to tapping other than by hand. It's possible to tap with the aid of the mill, lathe, and CNC. All the steps before tapping the hole are repeated before these procedures: