Drilling Steel Bumper?
 

I have an aftermarket bumper that is rated for a 7/8" clevis D-rings. I ordered 7/8" D-rings, but it turns out the hole for the shackle mount is about .02" too small. I am thinking of buying a 7/8" or even a 1" bit to try to ream it out. Anyone see any problems with drilling the 1" hole? Should I stick to the 7/8" hole? Will I be able to do this with a standard 1/2" chuck hand drill? This is a pretty thick piece of steel I will be drilling. I don't have much metal working experience, so any advice would be greatly appreciated. Thanks!

Also, do I need to use oil while drilling? It seems I remember from 17 years ago in high school shop class using oil when drilling and cutting thick pieces of steel.

Two things come to mind from someone who has been a machinist for 30 years. The first problem may be finding a 7/8ths bit that will fit your 1/2 inch chuck without having a shop turn the shank for you. The second problem could be a safety issue, if your drill motor is really stout and that bit grabs, you could get the twist of a lifetime on your wrists and arms. There is no physical reason that the hole can't be drilled out larger but be aware of these two things. If you take a stone and rub it on the face of the drill's cutting edge to take some of the sharpness off it you stand less of a chance of getting the hook. Hope you have success in your project.

That is a wee bit scary to me as my profession requires me to work with my hands all day. A wrist sprain could be very devastating! Hmmm, I wonder if I take it to a body shop if they could do it for me?

Yes, I have found a bit with the proper cut down. Just worried about the grabbing thing...

Have you considered a dremel tool? You may just need to hone down the paint or powder coat that is inside the hole. Or maybe go to a 3/4" D ring. :dontknow2:

When I got my rear Mopar Bumper the holes were too small. Used the Dremel with grinding stone attachment and fixed it in 5-minutes.

X3 on the safety thing. You could actually even break wrists or fingers.

If you are .02 off then this is what I'd guess at.

1. the edges of the holes have a lip that needs to be cleaned off. A tapered reamer or pocket knife can do this.

2. The paint on the inside, as another has suggested.

3. The easiest and fastes solution. Take some sandcloth or crocus cloths and sand down the bolts that feed through that puppy. It should take you far less than 15 minutes and you'll wonder why you ever asked the question in the first place. ;)

Drill slow, if it grabs it won't be such a twist. Just gonna take a while longer to drill out.

That's funny, with a 7/8's bit you have to drill slow, and the torque on a 1/2" drill can slap your hand between the drill and the bumper and you'll be praying for help with a very LOUD voice.

Be safe, not sorry.