Punching Holes in Sheetmetal

Well, there's the Whitney punch, but the only one I've ever used had about a 2" deep throat, and only round dies.

Have you looked at metal that's already perforated?

Good Luck! Rich

The only simple low-tech method that's worked for me is to clamp the sheetmetal between two heavy steel bars with the cut line at the top edge of the two aligned bars, and shear the metal with a chisel.

It works pretty well with a bench vise with hardened jaws, not so well with mild steel because the chisel gouges them. If the rear bar doesn't have a sharp edge the metal will be smeared back over it, so you might want to rough the holes out undersized and nibble or file them to the lines.

I cut the slots and louvers in this catalytic converter heat shield this way:

removed the folding bar from my home-made bending brake and adjusted the clamp plate even with the edge of the lower frame. that brake the frame and clamp are replaceable angle iron that bolts to the machined ends, so it can tolerate abuse like this that would permanently damage a commercial unit.

Here's a manual punch for sheet metal up to 24" wide:

punch and die geometry is simple enough that you could make them, if you are good at hardening and tempering tool steel.

jsw

How available are fly presses in the US, I think maybe you call them screw presses. In the UK they are quite common and can be bought fairly cheaply and the tooling is easy to make. I love having one for all sort of press operations. Unlike a hydraulic press you get some feedback which is useful for some operations.

This is the common type of small press here:

The ram can be drilled to hold a punch. Dies are more difficult. The Roper Whitney press holds the die between two pairs of opposed setscrews, which requires careful, fussy alignment and isn't really secure enough to allow nibbling.

jsw

I was thinking of this sort of press

, quite common in the UK and the ram is accurately located unlike a typical arbor press and especially the cheap Chinese ones. The ram typically takes a 1" diameter arbor on the tool although other fitting are around. I had to bore the ram on my Sweeney and Blocksidge fly press to 1" as it used a different fitting. I think mine weighs about 250kg and is rated about 6 tonnes although they come in a wide range of sizes.

We used to have those here, but the people who operated them all got brain damage from repeated concussions. d8-)

I did work at a place with one and it was a on the low side so the workshop foreman joked semi seriously that a crash helmet was essential safety kit. I'm 5' 7" and my press is set at a comfortable height and the balls are above my head so short of walking into the handle and bar it's not a problem for my. I just set the ram stop when it's not in use so the bar and handle are positioned to the side and out of the way when not in use.

BTW I recently got a bargain on eBay in the way of 2 sets of round punches for a press, 68 punches and dies 2mm to 35mm and another set of

34 punches and dies doing 3/32" to 2" but not in any standard increment. I was lucky and spotted them and the guy had a buy it now so I thought about it for a bit and snapped them up. The price was very good and they were located near a route I use regularly so I picked them up. Some have seen some use and other appear unused. Just need to make a bolster for the dies and an punch holder for some of the smaller ones. I've seen sets like it before and they seem to get snapped up and split then reappear individually.

You can buy punches from Roper Whitney in lots of shapes but they will be $40-100+ per set of punch and die so it will get expensive fast, and then you need a press with enough force and enough throat for the size of your sheet. You could use Greenlee style punches, where you drill a pilot hole and use a bolt to pull the punch into the die, but they make the Roper Whitney stuff look cheap :-). If your sheet metal is thin enough, can you use a RotoZip type tool? Won't get square corners without filing or a nibbler, but it should cut fast and you can set up a guide template to get accurate and repeatable cutouts.

----- Regards, Carl Ijames

Your best bet is to make your own punches out of some hardenable tool steel and punch single sided against a sacrificial wood backer.

It probably would just shear the top of my skull off.

'Sounds like a good one, David.

If it were me, id have a quiet word with my laser profiler. He does lots of work for me and he might just think it fun to write the DFX file for lots of different shapes and laser them out when the machine is not making money. You will need to find a laser profier near you and go and have a word. Let us know how you get on. Its amazing what our better halves think up for something better to do!! Ted Dorset UK.

In terms of getting shaped holes, why not oxyacetylene? The spark-making is fun, and the edges get a nice rounding. Some metal coloration should be expected (can be integrated into the design, or painted over).

If you sort out the punching, an interesting effect good for preserving dark skies would be to position the punched out pieces aligned with the holes inset maybe 1/4" via tacked wire standoffs or other means. The cutouts would show up better without glaring in your eyes. One could apply contrasting finishes (or none) to the cutouts before tacking them in place. Fiddly, but I bet it'd look nice. Leave the bottom of the sconce open and paint the inside white.

Pete Keillor

I was wondering about suggesting that, I've not had any done recently but have had many jobs done by Freshlook Engineering in Frome and just email them a DXF file drawn with QCad and wait for the bits to be cut. I'm local so just pop in and collect the parts.

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And whether this is reasonable is a function of whether you have a lot of similar holes to make, or just one.

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Or -- you can pick up flywheel presses in ratings from 1 ton up. Be really careful -- those things don't know the difference between whether a hand is in the way or not. Just punches on through and resets in a very short time.

The tonnage required is a function of the thickness and the length of the cut (circumference if round, perimeter if not) -- as well as the material to be punched, of course. You can find the formulas in _Machinery's Handbook_ -- and other places if you don't have that.

Good Luck, DoN.

:

And also if you can convince her to exercise her creative ability by designing and milling out the punches herself.

jsw

Steve B wrote in rec.crafts.metalworking on Fri, 6 May 2011 20:49:54 -0700:

I think you would be better off with a plasma cutter and a few templates. Punch an dies will cost a lot, and the press to use them isn't cheap either.

May I show your post to my wife? I'm trying to get a new plasma cutter....... Thanks, tho. I'll bring that up the next time she tells me she wants all these complicated expensive sconce lights. I saw some great ones at Temecula Creek Golf Course and Hotel. They were massive, and looked like

22ga. metal that had been cut with a #5 cutting tip. Very rough. The OA torch is an alternative, and I've been looking for a small one. Still, the plasma would be nice.

Steve

Steve B wrote in rec.crafts.metalworking on Sat, 7 May 2011 22:05:41 -0700:

Sure. And once you get one, you won't know how you lived without it. I recommend Hypertherm. Made in USA.

A plasma cutter will leave very clean edges if you can move fast enough. I've made several templates for various shapes to make the sides for several johnston solids and platonic solids.