I experimented with all the method suggested, cordless power drill, the pneumatic wrench, even auto tapping machine. But like Gerald, my favorite goes to hand tap using spiral point bits... After a few slanted tap holes & a broken bit, like cycling, everything just went on without a glitch. The monotonous back & for turning action with timely squeeze of WD40 is calming to the mental health. Also its easy on me ears & no need to dough flying chips. :D

Tap all the holes on the main beam takes less then an hour,,, not too slow in my opinion. Just grap a stool & its really comfortable.;)

Ken, Sorry you didnt enjoy the Pnuematic Wrench. Almost everyone I have shown enjoys tapping that way. I will agree that it gets kinda loud but I just throw on my Ipod and some ear muffs.

Russel,
don't get me wrong, your wrench method is fast. It will be my 1st choice if mass production is involve. Just that I do work late into the night, so hand tap helps to keep complain down :D

PS,
I have a boom box in the shop, I don't like to expose to the danger of loose ear phone wire entangle with anything while working, it can be dangerous at times. Moreover, I feel secure when I can hear whatever that is happening around me... Just some of my hard habits...

Okay Ken, I think we have another misunderstanding; My favourite is NOT handtapping. (I go cordless drill just because they are normally lying around)

Ooops, another blunder, sorry Gerald.

Depending on the thread pitch I do this operation before tapping.

Is it an idea to pass the tapping head through a block of wood to help keep it vertical?

That can work.

I have seen that done before. Here are some cool ideas.

http://www.rockler.com/blog/index.cf...E0FA7D26277FE0

if you have a standard tap start with that and finish with a bottoming tap. to keep it straight by hand is just practice. it isn't to hard if you take it slow.