This is the dimpling tool I made for tight locations, such as the tips of the rudder top and bottom ribs. As you can see, it's made from a "C" clamp. I have drilled and countersunk a dimple die into the left-hand end, and replaced the "foot" with a 3/16" hole to hold a dimple die.
This view shows the dimple die in the end of the jackshaft a bit more clearly.
And this view was meant to show the die machined into the clamp body, but unfortunately it's pretty blurry.8BIM
Here's the 3/16" hole I drilled in the end of the jackscrew, to hold the dimple die. To find the center of the shaft, I placed it in the chuck of a drill, spun it, and marked the center with a Sharpie pen. Then I center punched it and drilled it by hand. However, I found a much better method when I made my countersinking tool (described below).To get the jackshaft into my drill chuck I had to remove the "T" bar. I did that by cutting off one of the flared ends. When I was finished machining the shaft, I put the "T" bar back in and re-flared the cut-off end by squashing it in my vice.
This photo is meant to show the drilled and tapped hole I made for my countersinking tool. I apologize for the blurriness.To make the dimple countersink in the clamp body, I needed a way to extend my countersink bit so I could get a straight shot through the jackshaft hole. I drilled and tapped a hole in the end of an exacto-knife handle.
While making this part, I discovered a neat trick that ensures you get a hole well-centered in the shaft. First I placed the shaft in my drill press. Then I spun it a low RPM (around 500, I think), and found the center with my auto-center punch. Basically, I found the spot where the punch didn't wobble. I made a centerpunch mark while the shaft was still turning in the press. Next I drilled the hole, starting with a small bit and working out in stages, while the shaft was still turning in the drill press. So, in effect, I was using my drill press as a vertical lathe. This worked very well, and the resulting tool (next photo) spun very true.8BIM
The resulting countersinking tool.