Slow Progress on the Telescope Mount

The squares that will hold the needle bearings need 6-32 holes both for set screws to hold the bearings in place and for screws to hold the square in the ends of the two housings.  

A single screw to do both would be attractive but I could not find one exactly the right length without using ugly washers on the outside of the housings.  Even then, trying to turn in the screws to do two different tasks while maintaining alignment seemed troublesome.

So, I used my .1065 carbide drill bit to start.  I used the adjustable slide stop that I made a week or two ago to hold each square in the same relative location to avoid having to keep swapping edge finder with drill bit.

You may wonder if each of these squares was so similar in dimensions that I could get consistent results.  In truth, no, but this is why when you are holding a threaded part inside another assembly, you make the hole in the larger assembly a bit larger than a through hole.  If the tapped hole is a few hundredths off, there is enough wiggle room for everything to fit well enough.

Four holes per side, four squares.  A short gCode program to drop the drill bit to the top of the workpiece, then .4" down at 1 ipm and then out again.  Turn the workpiece 90 degrees and hit Run again.

Next step: use a reamer. If this term is unfamiliar, a reamer is a very precisely sized, very exactly concentric cutter that is encouraged when tapping carbide.  Same program but after setting z to 0 for the reamer's length.

Next step: I thought that I had bought a 6-32 carbide tap. No.  If made in USA they are $100 and up.  I did eventually find a German made one on eBay for about $25.  It will be here in a day or two to tsp those 16 holes.