Expand hole in steel?

[knuckle-dragger]

I have a grating which is held down by two padlocks which go through a hole in the part that is cemented-in and the other side through the grating itself. Unfortunately the holes are about 3/8 inch diameter (poor design by the contractor) so this makes it hard to get the shackle properly lined up and the padlock closed. I want to expand the hole to around 3/4 inch. Oh, BTW the steel (mild) is about 3/8 inch thick.

What tool can I use? I don't have the luxury of removing it all to a machine shop and using a boring machine or an arbor press and a punch. I have to do it in place using hand tools but from prior experience I know that if I try to feed the 3/4 inch bit through the 3/8 inch hole it'll immediately seize and likely break the bit. A step drill will be far too small--only good for sheet metal really. Do they make some sort of tapered drill bit like the old-fashioned type for wood screws? Where would I look and what would I search for?

[Steve Barker]

Cutting torch. AKA blue tipped chisel. AKA acetylene sixteenths

[Gordon Shumway]

Do the job in small increments. Start with a 7/16, then a 1/2" etc.

[Steve B]

It's called a reamer. Google "reamer".

Steve

[Tony Hwang]

Hi, Reamer?

[notbob]

Rat-tailed file. Been kickin' ass and takin' names since the 16th century. You'd be amazed what the right file is capable of, specially on soft steel.

nb

[Evan]

Use a padlock with a smaller diameter shackle with a longer length...

Rather than expanding the holes make the thing you are threading through them smaller and longer and therefore easier to line up...

~~ Evan

[elliot]

The material to be removed is steel, not concrete?

[jw]

Yep, both of these will work. Buy lots of dremel bits. But for the cost of those bits, you might be able to rent a cutting torch for an hour and do the job in minutes rather than spend many hours.

[Jon Danniken]

The only problem you will have with a step drill is that the hole won't be

3/4" all the way through; it'll be 3/4" halfway, then the next step (likely 7/8") the other half. You'd be surprised at the ability of a step drill; I recently enlarged several dozen holes in 3/16" plate to a diameter of 7/8" with the $20 step drill set from HF.

You will, of course, want to use cutting fluid when you perform the operation.

Jon

[George]

I will give you a 1 on a 1-10 scale for the troll..

[Nate Nagel]

Or just borrow a big hand drill with a 1/2" chuck and a 3/4 drill bit (I say borrow as these are Not Cheap) and drill it out. Make sure the drill has a handle for your other hand, and have a friend handy to drizzle cooling oil on the bit as you go. Use a slow speed to keep from burning up your friend's $20 drill bit.

good luck

nate

[dpb]

...

Does this seriously need to be held in place w/ padlocks????

Why not just a toggle or something to fit the holes or just tap and a stud?

But if it's just mild steel, there should be no problem in using a regular twist drill in a couple or three steps at most. Surely 3/4" would be overkill for alignment if a 3/8" currently will work at all, anyway.

--

[Joe]

All of the suggestions so far are way off base. The tool you need is called a tapered reamer. Anyone who has worked construction, steel structures, railroad bridges, whatever, knows that this how you deal with misaligned holes. There is a hand operated version of this tool in the Grizzly catalog on page 349, item H5890, $4.98. The sizes maxes out at 5/8", but this should work for you. You're welcome.

Joe

[Steve B]

All of the suggestions so far are way off base. The tool you need is called a tapered reamer. Anyone who has worked construction, steel structures, railroad bridges, whatever, knows that this how you deal with misaligned holes. There is a hand operated version of this tool in the Grizzly catalog on page 349, item H5890, $4.98. The sizes maxes out at 5/8", but this should work for you. You're welcome.

Joe

Excuse me ................ If you look back, I was one of the first three responders, and suggested a google search for "reamer" which leads to a wiki explanation, then multiple pictures of multiple types of reamers. Any steel person learns the first day what a reamer is. Some of these responses have been hilarious, I agree with you on that.

Steve, former steel erection contractor.

[CraigT]

I'm not so sure that the drill bit will grab going from 3/8" to 3/4", that's

3/16" on a side and might not grab. However, let's say you're right. Do you have a bench grinder and do you feel comfortable grinding the cutting edge of a drill? The way to eliminate the grabbing of the drill would be to grind very small flats across the face of the cutting edge so that the leading edge of the drill cutting edge is almost vertical (negative rake). By doing so will mean that it will require more pressure to push the drill through and the chips will likely be little crumbly blue ones, but this will work.

[Steve B]

"CraigT" wrote

My experience with hogging out holes is that I have to go in increasing sized holes, particularly with larger diameters. Anything that is more than about 25% bigger than the previous hole doesn't work very well. The exception is when working on a drill press, and sometimes, the bit just does work, but lots of times, it grabs and doesn't work. I have a Skil that will put a hurtin on your shoulder whenever it binds.

I'd use a reamer, and be done with it in less than a minute.

Steve

[knuckle-dragger]

No can do. The hole in the part that is cemented in is about 1/2 inch from the wall, thus the shackle has to swing to the down position in this distance. Hard to explain but I've tried what you're suggesting.

Further I'm limited by the availability of rust-proof padlocks. I already have two padlocks that fill the bill by means other than coating it. Coatings would make the size of the hole even larger.

Already I'm at what I consider to be the bottom limit thickness-wise for reasonable burglar proofing.

[knuckle-dragger]

I already have the necessary drill and the bits. It's breaking the $35 bit that concerns me. (And doing it again with a new bit and expecting a different result.)

[knuckle-dragger]

Do you see a man under every bed, too?