I have used a piece of 2 by 4 to guide both the drill and the tap.
Wood like aluminum is easy on the drill and tap. I might be tempted to
keep an aluminum block for the day when I need to tap another hole, but
wood blocks get recycled in the wood stove.

Dan

Ecnerwal wrote:


Don't know about that, sounds complicated. Might or might not work (only
1/2" for it to work on). Standard method in the labs I've worked in has
been to have a handy block (several inches thick) with various holes
drilled through (on a drill press) which could then be clamped to the
workpiece and used to guide the tap "pretty precisely". Generally
aluminum, so it will bugger itself up rather than the tools it's
guiding, and was cheap/easy to make another one of if needed. Guide the
drill, too, if needed (in a smaller hole, or use bushings). If you have
money to splash about or a deep tool crib, a mag-mount drill might
provide a handy tapping jig which you can take to the machine and drill
the hole with, too.

If you _really_ need "perfect" alignment, threads are probably not the
solution, so I expect that if threads will do, the tap-guiding-block
will get them started "perfectly" enough.

--
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