The Stovebolt Site Forums The Shop Area Paint and Body Shop drilling spring steel

I need to enlarge the front bumper bracket holes on my '36 gmc. None of the drill bits that I have will touch it. I went to the tool shed here in town and asked for a bit that would work, bought it and guess what? wouldn't touch it. I have tried heating the area around the hole and that didn't help.
So what's the trick, my grinding burr's don't seem to work either.
Anybody got any idea's?

You've found that the bumper bracket are spring steel that's pretty much harder than woodpecker lips. You'd have to heat the area around the holes red hot to take the hardness out of them, but doing that would compromise their strength. An abrasive burr (not carbide or high speed steel) would probably work, but it would still be slow going. Or a plasma cutter, but that might affect the strength as well.

The last time I had to do this was around 40 years ago and I used a high quality drill press on the slowest speed possible (around 100~150 rpm) with a masonry drill bit. The more speed you use, the less likely your chance of success will be. The larger the size of the hole, the less likely your chance of success will be. If you're using a handheld drill it will never work for you. If you're using a cheapo Chinese Harbor Fright drill press all you'll do is shake it apart and you might break the bit. Probably a cutting torch would be better. Good luck.

if you are near grass valley, ca go here and ask them. bet they do it for cash while you wait. Palmer Enterprises Truck Repair

Why do you need to enlarge the holes?

Is Palmer enterprises on E. Bennet? I need to enlarge one hole as it is not centered when attaching the bracket to the frame. It's off by about 1/8". I thought about the victor wrench but that just looks like a backyard redneck did it I'll get some deburring tools and whittle away at it.

That's weird. It was incorrectly made at the factory?

If it is only off by 1/8", can you tweak the bracket to make it line up? I'll bet it is bent slightly and given the right approach you could bend it to fit.

Can you enlarge the hole in the frame to make it work? The frame is easier to drill or grind or file.

That!

Or maybe you need one of these.

Use a die grinder and a cone shaped stone, or a diamond dust burr. Ditto on elongating the frame hole- - - - -it's not as hard as the spring steel bumper bracket. Take your time and be patient- - - - -at die grinder spindle speeds, trying to force too fast a cut will make the bit chatter.
Jerry

Nothing I can do with the hole in the frame, it's a 2'' x 3'' mounting pad with a threaded hole in the center. So my only option is to enlarge the hole in the bracket.
The bracket is one piece and attaches to the ends of the bumper and then to the frame rails. I take a picture later today.

Well dumb me figured it out. I installed the bumper and the spring bracket about a year ago. I making a bracket for the front license plate, so I pulled the one bracket bolt off and then I couldn't get the bolt back in, So I'm scratching my head and thinking I didn't have this problem before and I remembered that I mounted the bracket to the frame first and then attached the bumper to the bracket. So I took the bumper off ( only 4 bolts, 2 at each end ) and what do you know, the holes lined up. (slap forehead). So no holes had to be drilled or wallowed out.
It's the crappy to get old and feeble.

I'm glad to know that GM didn't make a mistake on the bumper.

I've got an old service manual from the 1930s stashed away somewhere that shows a bumper bending jig in use for installing a spring steel bumper on a vehicle. The bumper is almost straight when it's unloaded, and it takes a jackscrew device about 3 feet wider than the car to bend the bumper to the right arc to bolt it to the frame brackets!
Jerry