For a perfectly round hole with clean edges, what’s the best method? A metal cutting hole saw? Or some kind of punch and die arrangement?
Would this punch and die set work well for that?
http://www.harborfreight.com/9-piece-punch-and-die-set-95547.html
What about this bi-metal hole saw?
A hole saw with a good drill press.
A punch & die will require a hydraulic press.
The nice thing about the hole saw is that the outermost point on the saw will always create a perfect circle, as long as the metal is securely fixtured, flat and on a drill press. Doing it by hand will never come out as good.
Metal hole saws will leave a ragged edge that will need to be smoothed, George.
The punch set you posted, I think is a variation of this;
automationdirect.com/images/products/medium/m_1097010.jpg
A knockout punch like this will give crisp clean holes but needs a pilot hole. Any hole punch will still need to be smoothed, but much less. The tool you buy will depend on how big a hole you need.
You also might consider a step drill, like this;
i21.geccdn.net/site/images/n-picgroup/IDA_35-517.jpg
Can de-burr each hole with the next size on the step. It cuts a little chamfer on the hole. You can switch sides and use it to chamfer the backside as well. If you can get the hole size you need with it, this is a pretty fast, quality solution.
They have a version of that setup you posted in your first link too. I don’t really understand how it works. But I don’t understand how the punch and die set works either. Do you really press a metal punch down on some holes drilled in a plastic base? Or am I missing something? I like the uni-bit idea. That way no matter how the initial hole is constructed, I could clean it up to be perfectly round with the uni-bit.
A knock out punch set.
But these aren’t cheap.
Center punch where you want the hole. Then with a compass, scribe the desired hole diameter.
Then with a hole saw slightly smaller than the desired hole, as hole saws aren’t all that accurate, create the hole. Then with a die grinder with a small sanding drum, enlarge the hole to the scribe line
Tester.
What about dropping by a HVAC shop with the piece in question (if possible) and ask them about knocking this out for you? Seeing as how they work with sheet metal every day odds are it’s no big deal for them and they may charge you little or nothing to do it; depending.
A couple of years ago I needed a sheet metal box made and since I don’t have, or need, a press brake and tools of that nature I swung by a HVAC shop and asked them to do it. Five minutes later I had my perfect box and they refused to even accept any money for doing it.
It was just a “Nah, keep us in mind for HVAC work”.
it the metal is thin, hole punches work fine. I used to use them to punch holes in an Al chassis for vacuum tubes.
“I used to use them to punch holes in an Al chassis for vacuum tubes.”
Ah, yes, BillRussell. I remember Greenlee punches from my youth. That is, the hand-cranked kind. In fact, I borrowed one about a year ago to make holes for a bunch of SO-239 connectors.
GSJ – They are available, but rather pricey, on eBay, both the hand-cranked kind and hydraulic. Hand-cranked were good for about 18-ga steel.
I think OK4550 has good advice.
Ah, the Greenlee chassis punches. I used to use them a half a century ago when I built vacuum tube amplifiers from scratch. They made perfect holes.
Guess I’m showing my age!
There is a Unibit that drills 1"
http://www.irwin.com/tools/drill-bits/high-speed-steel-fractional-hole-enlarging
Well just my two cents worth. That harbor freight deal would only be good for thin shim stock, if it were a quality tool which I’m not sure it is. The hole saw will drill a hole but it will not be particularly smooth. (Again I would question the quality from HB. I bought door latch set from Menards to install a dead lock at the cabin, and the bit was so bad it wouldn’t even cut through one skin of the steel door. Luckily I had another hole saw along.)
I’m not familiar with the unit Tester showed but that’s kinda expensive depending on how many you are doing. A hydraulic punch press with the correct dies will provide the cleanest and fastest if you want to use the donut hole. Again depending on the quantity, visiting a machine shop or HVAC shop, depending on the guage, might be your best bet.
These http://www.zoro.com/greenlee-hole-punch-set-10-piece-10-12-ga-steel-7235bb/i/G1705137/?gclid=CKSq1JKQmsoCFQuLaQodsg0G2w&gclsrc=aw.ds are similar to what others have posted. They are good in tight places where the workpiece is still part of the car, and a little hard to mount in a drill press. See if you can rent or borrow a set. I borrowed one from an A/C shop to run freon hoses thru a firewall for an under dash unit about 40 years ago.
that should be “vacuum tube sockets”, sorry.
Thanks to all for the great ideas. I gave it a test today using a hole saw (for metal) . The hole came out perfectly round, but had a bunch of burrs. When I tried to remove those edge burrs with a dremmel tool, I ended up w/ clean edges but the hole out of round. Also the hole was a bit off center from where I wanted it, the hole saw’s pilot bit drifted a bit from the starting hole punched. That’s not a big worry, I can do a work-a-round for that.
For the application it is critical the hole be perfectly round, the diameter or exact position of the hole is not as critical. Unless I come up with some kind of rotating fixture to use in conjunction w/the dremmel, I don’t think I can get the required degree of roundness with that method. I’ll think I’ll buy a uni-bit and try that for the next test.
Yes, I realize the simpler method is to take it to somebody who has the exact tool that does this. Why don’t I? Remember that tv advertisement years ago where the mother is doing a show and tell, explaining to the daughter how to keep the household in order, and the daughter screams “Mother! I’d rather do it myself!!” … lol …
If you need perfectly round holes in sheet metal? Look on craigslist.
I got a set of Greenlee punch set for fifty bucks.
Then on Craigslist, I got a a JET floor drill press for a $100.00
All we had to do is lift it over the fence from the neighbor and carry it into the shop.
Tester
I agree, the Greenlee punch set is best for this.
@Tester … @“MG McAnick” posted a photo of a Greenlee punch set, presumably similar to what you mention above. Just curious, how does that tool work? Do you drill a pilot hole first, then the two halves screw together, one on each side, threading through the pilot hole, and by turning with a ratchet while holding the whole thing so it won’t turn somehow, the pressure bears down and sort of squeezes the sheet metal until the hole pops out?
Think of it as of it as a sheet metal shear. Only for round holes.
You drill a hole to fit the forcing screw.
Then you couple the cutter and receiver.
Then as you turn the bolt, the cutter cuts the metal and the receiver accepts the slug.
Tester
Thanks for the clear explanation, that makes sense.
WOW @Tester, That was a good buy. Someone has a Greenlee set with a TINY hydraulic ram for $600 on my local list today. I’ve never seen one like that. Nice tool, but I think I’ll pass.
