Friday, December 4, 2015
Wrong Size Drill
I have been working on a new model of ScopeRoller; actualy two different new models. I was struggling to tap 1/2:-13 threads in an aluminum block, and I figured out why. This size tap uses a 27/64" drill bit (.422") When I first started tapping this size, not having a .422" drill bit, I used a .408" bit. That works fine when tapping acetal; but not for aluminum. As a temporary measure, I used a drill bit that would give me a loose fit. What a difference! I am replacing the tap and buying a .422" bit. The tap is still fine, but sharp taps are a joy to use.