Tip: Step drill in tight spots

Will share another tip.

When needing to install snap bushings between ribs aft of wing spar we need to get a step drill in there to drill the hole to the correct diameter. A step drill works well for these larger holes but spacing of ribs is about 4.5 inches and a drill or commercial angel drll attachment takes up too much space when coupled with a step drill.

The angle drill kits we typically purchase with our rv tool kits usually drill up to 1/4 inch and chuck is too small to mount the step drill.

Solution

Take a 5/8 diameter or larger brass (or steel) rod about 1-3/8 inch long. Drill a 1/4 inch hole in one end and 3/8 (or shank dimension of step drill) in the other end. Drill and tap set screws that will be used to secure drills in the newly drilled holes of the bushing.

To use the tool install a 1/4 short bit in the angle dril and slide over your new bushing onto the drill bit. Secure the set screw (if the hole in the bushing is long enough the set screw will bit on the shank of the drill). Now place the step drill in the other end and secure it by tightening the set screw. The assembly will fit nicely between the ribs and you are off and drilling.

Attach your angle drill to to you air or electric drill and you can start drilling holes for bushings and grommets at will.

Let me know if this is not clear and I can include a photo.

Another option is to get the Harbor Freight step drill set -

http://www.harborfreight.com/3-piece-titanium-nitride-coated-high-speed-steel-step-drills-91616.html

- and grind away the corners of of the hex shank so it will fit in a small size HF angle grinder -



The pic shows a smaller true Unibit, but the HF set comes with larger steps and a 1/4 inch shank - the true Unibits have a 3/8 shank for the larger sizes.

I just tackled the same job, ended up buying a pencil grinder. It worked pretty good, very easy to use and well worth it.

I chucked up a step drill in the lathe, turned down part to the hilt, then cut it off. It fits in the Avery angle drill chuck. The red part marks where to stop. Not a big deal, but it took me a long time to think of it. I use it a lot!