EAA Sport Aviation - November 2010

HANDS ON

HINTS FOR HOMEBUILDERS

Drill Press Dimpler

BY JOE NORRIS

IF YOU’RE BUILDING A sheet metal aircraft, you will undoubtedly run into a situation where a flush head rivet is required. In order to get the rivet head flush with the surrounding metal, you’ll need to either dimple or countersink as appropriate. For thin material (less than 0.04-inch thickness), dimpling is required. If the rivet location is close to the edge of the part, you can use dimple dies in your hand rivet squeezer to accomplish the dimpling. If the location of the flush rivet is farther from the edge of the part, there are a couple of solutions.

If you have only a few holes to dimple, you can use your hand pull rivet gun and dimple dies that use a nail as the mandrel for the gun to pull. But if you have a whole wing or fuselage skin to dimple, this hand method can get old quickly, not to mention use up a bunch of nails. There’s a better way.

Many aviation tool vendors sell a tool that is designed to dimple holes away from the edge of the part. These bench-top dimplers can cost more than $200. Sometimes a number of builders will share one or maybe your chapter tool crib includes one. If you can’t find one and you need to get some dimpling done, you may have the perfect tool in your shop already—a drill press!

You’ll need to make a slight modification to the table of your drill
press to use it for dimpling. Drill a small hole in the table that will
accept the stem of the dimple die. Just put
the appropriate drill bit in the chuck, move
the table up close, and you’re set to drill the
hole. Make sure to pick a spot that will
allow you to get at this hole from the under-
side of the table. This allows for easier
removal of the dimple die when you’re fin-
ished with your dimpling. The hole should
be a snug fit for the dimple die stem, but not
so tight that you have to drive the die into
the hole.