[GeeTwo]

Originally Posted by AdamHeard

This actually a pretty neat idea.

Thanks; Gixxy and I invented this process for the front panel of an 8-bit adder for his junior research project, and the team and I have continued developing ever since.

Originally Posted by GeeTwo

This stuff. ..making a passable oval slot with only a drill press and hand file.

To elaborate, for an offseason drive chassis, we needed some 1/4" slots which allowed at least 1" of travel (to tension a chain run). We did this at 1.2" of travel (this technique requires a multiple of 0.4"). The attached image shows the four stages:

1. First, do the 1/16" pilot holes every other hole for the travel length
2. Then, remove the template and drill 1/4" holes for every other hole, including each end hole
3. Follow up with 1/4" holes for the remaining holes (it is critical that the piece be lined up to the bit for this step, or the bit will fall out of the tiny hole into one of the large ones, or off to one side)
4. Finally, use a flat file to knock off the scalloped edges. If you are not careful, you will wind up with a nearly rectangular hole rather than a nice slot with semicircular caps. It will still work, but won't look as nice.