Expand hole in steel?

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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.)
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Well, yes AND no. When drilling into fresh metal, there is even a sequence, sometimes requiring a smaller pilot hole to even get a big drill to start cutting. Then, as with cast iron, if this is cast iron, the rough surface of the metal can cause chattering and jumping. Drilling a hole in this stuff is going to be "fun". I have enlarged many holes, and sometimes it goes like a breeze, and sometimes, it's a dog fight. You won't know until it's over. Saying it's going to be easy is optimistic. I hope it does go like a breeze for the OP. Sounds like a restricted space, and those high torque drills and big bits can put a hurtin on you. I had a Skil that wasn't very big, but got my shoulder GOOD a couple of times. Years later I had surgery twice on that shoulder.
Steve
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High five dude.
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re: "Sounds like a restricted space, and those high torque drills and big bits can put a hurtin on you."
Why do we always hang on for dear life when a drill tries to take us for a ride? ;-)
I was enlarging a bolt hole in one of the brackets for my garage door tracks a couple of weeks ago. I busted one of the flat-head track bolts and the only spares I had were a larger diameter.
Anyway, it was in one of the upper brackets and instead of grabbing a step ladder so I could hold the drill at chest level (heck, it's only *one* hole) I just reached my arm up, fully extended, and started drilling.
I'm sure you can guess how it felt when the bit grabbed, I instinctively held on tight and the drill tried to pull my fullly extended arm even higher, in that familiar twisting motion.
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snipped-for-privacy@nowhere.gov wrote:

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
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On 7/22/2011 10:57 PM, snipped-for-privacy@nowhere.gov wrote:

I will give you a 1 on a 1-10 scale for the troll..
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Do you see a man under every bed, too?
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On 7/22/2011 9:57 PM, snipped-for-privacy@nowhere.gov wrote:

...
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.
--
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Yes, this is probably the most economical and practical way to go.
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On Jul 22, 9:57pm, snipped-for-privacy@nowhere.gov wrote:

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
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wrote:

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.
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This seems to be a tool for reaming out WOOD. It's on a page with spade bits and similar wood-only tools. Another problem is that it has to do the job in no more than 1/2 inch. Length looks a lot longer than that.
However, you have given me the name "tapered reamer" which sounds great until one looks at the prices. Just as with the gradual increment approach using drill bits the same technique is needed for tapered reamers but the cost...wow. By the time I reach the last stage (be it 5/8 or 3/4) we're talking $60+ for each increment and that's from MCS Industrial Supply. Although they do have a tapered brace reamer which might do the whole job and it's only $85 however then I need a tapered brace...
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wrote:

I have seen tapered reamers at pawn shops that were damaged for $2. From what it sounds like, you may have to shorten one if you bought one with too much penetration before engaging. Cut off the broken section. I have also seen them at yard sales for 25 cents. I have about a dozen, and don't have ten bucks in the lot. Don't use them very often, but when I do, they are a real work saver.
Steve Steve
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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.
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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
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snipped-for-privacy@nowhere.gov wrote:

If no one's suggested it yet, I'd vote for a 3/8" rotary file in your electric drill. Even better a carbide rotary file if you can afford it. Might take a few minutes, but you can easily "tune up" the holes tojust the shape needed.
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
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