Vintage Windmill and Wind Generator Forum

I've tried everything I could think of; from the inside, the outside, etc, etc... I ALWAYS have the bit grab and then my Milwaukee drill tries to break at least my wrist! Tower legs that use corner holes have caused me some pretty sore limbs and I've made some really ugly holes!

I've used a round file on the outside, filling perpendicular/across the outside corner.

There's probably a special punch for this. I just use a file and clean up as required.

May not be the right way but my plasma cutter makes it easy. Paul's way the better of the two.

Try starting with a small bit and increase the bit size very gradually. Might need to drill up to a half dozen sizes in increments.

OR take your angle grinder and cut 2 grooves on the outside angle, then using your grinder, angle it and clean out between your cuts.

I made this V block when I was still working in machine shop.
It can be bolted down on a drill press or a mill table.
Like Windy said, start small and work your way up to your
desired size. I also try to clamp the angle across the V block.

Kenneth

I have had good luck also using many bits sizes and bringing the hole up to the proper size slowly. Have drilled a small hole and used a die grinder also to grind it up to the proper size hole.

I use this jig on the tower angle iron legs and it works good. Use two clamps to hold in place.

Or just take a cutting disc in your grinder and do this. Depends on what you want the finished result to be. If it's going to be covered, do this. It might not be good if there is no bracket covering it, but it is quick to do.

I have used step bits with moderate success

Use a some worn grinding wheel but not cutting wheel. It gives the look of a round drilled hole without the broken bits and the off center results. I have a special grinder for this just as Peter as a special grinder that cuts gear teeth...

Ron Stauffer
Montrose CO