nonjic

spend the money on good quality, titanium nitride coated drill bits, they fall through most materials.

With a good quality bit and a very poor drill you can do alot more work.

If you have got lots of 20mm + holes to drill a "roto broach" magnetic 'slugger' is the best. these are like a little hollow milling cutter. They leave a little 'plug' of steel that falls through the plate. you can drill a hole in seconds.

Johns Top tip of the day...... if you are drilling a large ish hole with a hand held drill do not 'lock' the power on with the little side toggle, just lightly hold the main switch right at the end. if the drill grabs, which WILL happen sooner or later it stops (well massivly reduces the chances) of it spraining / breaking you wrist.

Blackbeard, If you havent already I would try out a few of the 'home made' hammers before you build one, if youve had a go on a Massey it is a world apart from any DIY hammer (and the new gereration of commercially available hammers) , you might end up very disapointed with what you build -

Bigger (seperate anvil hammers) can be bought very cheaply if you scout round enough - ( though obviously you will cop it on transport & installation costs :)

jmc - Im a newb here but have a bit of experience on making hammer bits, if you really want to increase the life of the dies I would dress some proper rads into the corners of the dovetails (especially the sow block) - you've got some major stress raisers there at the most common failure point.

Youve gone pretty sharp in the corners so you may have to undercut them a bit, but they will stil be a whole lot stronger than they are now.

If you use the edge of a blue flap disc in a 4 1/2" grinder you can get smooooooth rads real quick.