I've raved about the Tapmatic before, because it lets me use a drill/tap combo in my drill press to make one step 1/4"-20 threaded holes in aluminum. But I have often had problems with the 1/2"-13 tap in acetal (and of course aluminum as well). The tap just unscrews from the collet. What I did not see in the instructions, or did not remember, was that there is a backjaw as well. The square end of the tap is locked by the backjaw with a set screw. Amazing what a difference it makes.
I just finished making about 20 parts for ScopeRoller. These are square 3" by 1/8" wall aluminum sleeves that need a total of eight 1/4"-20 threaded holes at .5 and 1.5" from one end centered in each face of the tube. It was amazingly fast.
1. Mark the position of the 0.5" from end hole on the first workpiece with a caliper.
2. Put the end of the tube against the end of the drill press vise.
3. Start drill press.
4. Feed down while spraying some lubricant on the drill/tap combo.
5. Release handle after I hear the chamfer being cut.
6. Rotate tube 90 degrees, and repeat 2-5.
7. Repeat 2-5 for each piece.
Repeat 1-7 for the 1.5" from end hole.
I feel like Eli Whitney, or Samuel Colt (but I can spell and even my handwriting is better), or Henry Ford.
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