Starting Holes On Domes and The Ends of Rods

[Baddog]

Great idea for a handy drill jig!

Even if the bolt is proud of the surface, and the end flat, I don't think the cone will provide good centering because of the helical nature of the thread forming the locating surface. I would expect it to be off center by something less than a thread height. Maybe close enough, but less accurate than use on a dome or flat ended rod. But a similar purpose built tool could be made to encompass the threads for location (if enough thread).

I've used a similar approach to drill out bolts broken flush (or below) just by making what amounts to a limited use drill bushing with scraps of steel. The problem is holding location while starting the drill, so it's of limited use depending on context. Most often I've used a round bur on a die grinder to provide a pip for starting. And more often still, for larger automotive/tractor size bolts I mostly deal with, welding a nub buildup for grabbing with vise grips. Heat shock helps in many cases too.

In any case, I often find myself needing to remove/relocate brackets riveted to frames in my desert trucks. And pre-drilling the head for knocking off with air chisel is always a mixed bag for success, particularly when some areas don't have good open visibility and access. You can bet I'll be making one of those in steel for future use! I sure could have used this when I was cleaning up the frame for my current build a few months ago. Thank you!