I needed to cut 3.0mm diameter, 0.5mm spaced holes in the underside of the top plate of my INCRA Mast-R-. Raise the Lift-II router so I can attach the iGaging DigiMAG 6" Magnetic Remote Digital Reader. The holes could only be about 6mm deep because I didn't want to drill through the top of the board. Blind holes in aluminum with very small diameter are difficult as it is very easy to strip the threads if too much torque is applied The Irwin Taps did a great job The taps in the set have 3 different tips, one with a long taper, a second with a medium taper Taper and a third with almost no taper. I tapped each one into the holes in turn and ended up with very clean threaded holes almost to the bottom of the hole.