Simon, It might be worth a try to see if a small drill would survive. At least with 3D printing you don't have a cost like a new photo tool for an adjustment. I think if I had to drill the holes without a pilot, I would start them off with a slot drill in the milling machine and get as deep as I could with that then change to a twist drill. At least that should give a reasonably long straight start to the hole which should keep a drill on the straight and narrow. Jim.