Masking Threaded Holes

Question:

I recently read your column (January 2002) where you asked for other ideas on masking threaded holes. We have used two methods to solve powder buildup on the lead thread of a tapped hole. In many areas, we drill the hole, powder coat the part, and then use a Flex-Arm tapping table to tap the hole after paint. The extra wash operation after tapping is cheaper than the masking and unmasking time. The other method is using screws over and over to mask the thread. This definitely keeps the powder out of the lead thread. D. Z.

Answer:

These are great solutions. I sometimes forget that powder coatings are durable enough to withstand post-machining operations, such as drilling, tapping, etc. Many people have done this with great success. Using screws to fill the holes for masking purposes has also been greatly accepted as a good and cheap way to mask a hole. However, the larger the hole and screw, the more difficult it is to break the bond cleanly between the screw and the hole when removing the masking screw. Smaller holes do not present this problem. Thanks for the tip and keep those card and letters (email) coming!