Best Set-up for Drilling Holes Through Frame?

**JBWood05TJ** · 07-21-2007, 03:58 PM

Thoughts? Clearly a 1/2" drive with cobalt bit isn't it. I just found that out while drilling holes to install my new bumper. Whatta PITA.

Suggestions, please - I want to be ready next time!

**Jerry Bransford** · 07-21-2007, 04:07 PM

Drill a small pilot hole, then maybe one more until you get up to the 1/2" size.

valeech · 07-21-2007, 04:08 PM

What size are you trying to drill? Did you step up from smaller to larger sizes?

I have drilled the frame with Cobalt bits and didn't have any issues.

**JBWood05TJ** · 07-21-2007, 04:13 PM

He He - Nope! I went straight to the 7/16" bit!

Thought about starting with a smaller bit for a pilot, but for some reason had the idea that when I went to the large bit, it would bind up and jack me up.

Thanks for the advice - I'll use a pilot hole next time!

**jprcrpr** · 07-21-2007, 04:14 PM

Go wtth Jerrys suggestion. It will save you drill bits and alot of hassle.

hatch524 · 07-21-2007, 05:02 PM

a small amount of cutting oil helps keep your bits sharp. I like the oil in an aerosol can.

**JBWood05TJ** · 07-21-2007, 05:04 PM

Thanks, y'all. Appreciate the help.

zband · 07-21-2007, 05:05 PM

when your underneath make sure you wear glasses / goggles. steel shards hurt the eyes. Be prepared to fight the drill - when it gets through, the bit will bite into the metal and twist.

dirtbagofva · 07-21-2007, 05:15 PM

step bit also work well for drilling lager holes http://allprotools.com/store/page144.html

another option is a hole saw bit but, they only get down to 5/8 (though much cheaper than a regular bit)

Sweeney · 07-21-2007, 05:19 PM

Use a cutting fluid and low RPM . Cobalt has good high heat strength but you can still toast it... overheat the bit and it will loose its tempering. It's like cutting butter with, well, butter.

mbyron · 07-21-2007, 06:52 PM

Air powered drill....hands down the easiest Ive ever drilled a frame rail with...Lowes for like 45 bucks!!! And it comes in handy around the house (especially when building huge decks!!!)

CNY · 07-21-2007, 08:26 PM

Quote:

Originally Posted by dirtbagofva

step bit also work well for drilling lager holes .....

x2!

The 3 bit set at Harbor Frieght is amazingly good quality. And not just "good for the price", they are actually quite good compared to expensive bits.

jzmtl · 07-21-2007, 10:32 PM

Quote:

Originally Posted by mbyron

Air powered drill....hands down the easiest Ive ever drilled a frame rail with...Lowes for like 45 bucks!!! And it comes in handy around the house (especially when building huge decks!!!)

I don't think you can get a low enough RPM with air drill. When I was drilling my 1/4" rocker guard I was going between 60~180 RPM, the bit cuts off beautiful long spiral strand this way, not a single metal shaving.

I also have a cup with ice water in it to cool the bit periodically, and used gear oil as cutting oil. Ten holes later the bit was as sharp as new. And let you drill cool down often, they heat up fast when you drill that slow.

Also to minimize metal shaving clean up, wrap a big strong magnet in food wrap and place next to the drilling site.

**JBWood05TJ** · 07-21-2007, 10:48 PM

Thanks, everyone. I did mess up the first bit I got- $15 in the trash can. Live and learn. Well, now I know how to handle it better when I do rockers in a few weeks.

rmb2485 · 07-21-2007, 11:49 PM

Definitely start with a smaller hole but go up in sizes about 1/4" at a time, as the larger bit will bind if its too close to the existing hole size. If I were drilling a 7/16" hole, I would probably start with a very small bit then go for 1/4" and then 7/16". Invest in a center punch too; fighting with the bit walking when staring a hole is a sure was to get frustrated and do something like burn up a $15, 7/16" cobalt drill bit.

Having a nice drill helps a lot too. For thick steel like your frame, you're looking for something corded with low rpm's and a high amp draw. I have a 1/2" Milwaukee thats 8 amps and I think 800rpm.

As for lube, WD40 is really easy to use and it works fine for thinner stuff, but with something thick like a frame rail I would just use motor oil. Keep the bit lubricated with it and if you start to see smoke, give it a rest for a few seconds and lube up again.