To hold the centerline on the workpiece will help the device shown in the figure.
Recommend to read
THE CONDUCTOR-TELESCOPE
Of tubes of different diameter, tightly placed one on another, you can build a jig for drilling end holes in cylindrical rods of various cross sections. For the outer bushings are better...
CUT TRIPLEX
I am sure that many Amateur automakers in the manufacture of machines are faced with the problem of glazing of the body. Most of them come of the situation, "tied" to the size and shape...