I have need to tap a lot of holes. Most are 1/4x20 or 1/4x28 plus some smaller sizes. I purchased some very good quality spiral point taps to tap under power. I have already tapped about twenty holes with no problem but I am using an 18 volt battery drill to do it. It has a keyless chuck and doesn't hold the tap quite frimly enough. So, I made a tap holder that will fit in the drill without slipping so I can take full advantage of the adjustable slip clutch on the drill. Allen key shown on purpose.
This is a simple project but I was suprised to find that the shanks of the 1/4" taps are not standard. What's up with that? They (the six new ones I bought, two different brands) vary from 0.254 to 0.2555. Huh? So, I had to drill the tap holder with an F drill to accomodate the variations. It works.