Thanks for the jig design. This will be my first metalwork jig.

I like the dolly in the chuck plan. But I might be doing 50 or so at a time and I'm wondering if I can avoid taking the drill bit in and out.

If I bring the 6.9mm drill down onto the 6.5mm hole, that might centre it OK, do you think? I could position the strongback manually or slip a length of tube over the drill bit.