Presuming that you want to cross-drill for a pin …

Best bet is to find, or make, the matching female taper and use that as a jig.

Failing that … set it up very carefully in the Mill, and use a Slot-Drill to spot a nice flat face before you try drilling.

MichaelG.

Edited By Michael Gilligan on 21/07/2012 08:52:15

Wolfie

I wasn't trying to be clever, I just was unsure what direction you wanted to drill the hole.

A hole normal to the taper is easier than one at right angles to the axis as the drill has less tendency to run off, its more or less like cross drilling a parallel shaft. One way might be to put the taper in a vee block mounted at an angle (say clamped in the machine vise). You could use the steel rule trick to find the centreline. Start off with a spotting drill and you might not even need to centrepunch.

Ian

If it's important that the hole is on the centre-line, then what I suggested earlier is worth doing.

… spot the location with a slot-drill or a 3-flute cutter, before you commit to drilling.

This gives you one last chance to get the centering right, and it presents a flat surface to the drill.

… it only takes a little longer.

MichaelG.