Help with drill-Mill conversion

[irving2008]

Cheers, so I probably need a lock nut as well then? The original one just squeezed the inner race on to the step on the shaft.

The other problem is how to drill the hole in to the end of the quill for the chuck lock bolt. I foolishly thought it would fit in the lathe but that also has an M2 taper, Duh

Is it safe/accurate to hold a drill bit (facing up) in a vise and lower the quill down over it?

Safe - maybe if you can hold it tightly - drills have been used as lathes by holding the tooling in a vice and the workpiece in the chuck (I've done it).

Accuracy, its hard to see how you'd get the drill absolutely in-line with the quill. Here's an idea tho.
Acquire a block of MS say 50mm cubed. Drill an M4 tapping hole through the center of one face and tap M4. Put the cube in the vice with the M4 hole horizontal and accessible through the side of the vice jaws then drill down through the centre of the face with the drill you want to use to drill the quill. Remove the drill and without moving the vice put the drill shaft in the hole and lock in with a M4 bolt.

Remove the chuck and lower the quill onto the drill... careful with speeds and use coolant if poss.

You might need to grind a flat on the drill shaft to locate with the locking bolt.

The accuracy depends on how square the chuck was to the quill initially...

So, JohnS, Robin, BillTodd, etc (as real engineers) where's the flaw in my suggestion?