rectangulars hole in panel

I need to make a total of 44 rectangular holes in some reasonably thin aluminum. 22 of them have to be .56" x .52"; 22 have to be .81" x .52"

I had assumed I would be able to go down to harbor freight and buy a rectangular chassis punch; no, the cheap generic punches are all round, and the only rectangular punches I've seen are special-order for hundreds of dollars.

So... any good ideas (or sources of cheap rectangular punches!), or should I plan on a day or so with my nibbler and a corner punch?

Reply to
Joe Pfeiffer
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Since your holes don't look like a standard size, and are too small for a typical pull stud punch set, you're in custom punch territory anyway.

Depending on the tolerances needed you might consider plasma cutting with a template or CNC. CNC milling or routing would be another option.

A .5" square punch in a press might work ok if you can make several punches to get the full shape.

Reply to
Pete C.

You don't say how far from the edge or what size panel and if the aluminum is flat, but it wouldn't take too long to cut them out with a jeweler's saw with a swiveling blade holder if access allowed.

Reply to
Mouse

How thick is the aluminum? And how far are the holes from the edge? Can the aluminum be put an a mill or drill press? Can the panels be stacked so you can do 22 at a time? From your thoughts about a punch from Harbor Freight, I suspect the panels can not be put on a mill or stacked.

=20 Dan

Reply to
dcaster

I have a collection of old carpenter's chisels for this purpose. Grind a decent cutting edge to them and grind back 2 of them width-wise for dimensions of each rectancle. Then "chisel" through after marking , with a backing of roof lead sheet over steel plate.

Reply to
N_Cook

Aluminum, Thin. Hmm. Wood chisel, hardwood or aluminum backer, BFH (big ? hammer). Mark the lines, line up the chisel, hit with whacker beater, repeat.

Wes

Reply to
Wes

Actually following up to several different responses at once:

It's 22 of the smaller rectangles in one panel, 22 of the larger ones in a second panel. Some will be too far away for a jeweler's saw. I don't have good access to a plasma cutter (else the plasma cutter would almost certainly be the right answer) or mill.

The wood chisel idea is certainly worth a try.

Reply to
Joe Pfeiffer

You could punch a half inch round hole and then shear the edges square into the corners with the chisel on top and a steel bar clamped under the cut line as the lower shear blade. Tilt the chisel sideways so it shears the metal like tin snips

That's how I cut the slits for the louvers here

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I had just made this bending brake from scrap:
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with a better clamping cam:
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I clamped the sheet in the brake with the folding leaf removed and sheared along the edge of the lower frame. It's mild steel channel and was scarred a little but that doesn't affect bending. I aligned the hold-down bar with the edge of the frame and used it to line up the cut. Perhaps you could grind the edge of an old lawnmower blade square for the lower blade.

jsw

Reply to
Jim Wilkins

If the chisel approach doesn't work out, consider using a scroll saw. Typically they have a 16" - 22" throat and use 5" blades, with or without pins. I've used the same blades (without pins,

30 to 40 tpi, 0.014 thick, 0.30 wide, 5" long) on both a little Hitachi scroll saw and an 'Aven PS-21 Delux' jeweler's saw.
Reply to
James Waldby

Not seeing the original post and not finding it on Google Groups so don't know what the question was, but that said, if there is a need to make rectangular holes in thin aluminum of the kind typically used for instrument panels or the like, one possibility is a nibbler--you can get a hand nibbler for 7 bucks from Harbor Fright, or if you're got 18 CFM at 90 PSI an air nibbler for 30. Takes a little practice to get a clean hole but the cheap handheld nibblers work surprisingly well.

Reply to
J. Clarke

If the panels are only about .030 thick, a box knife might work well.

Dan

Reply to
dcaster

Two solutions that haven't been mentioned: punch a round hole, then use a coarse file to open it up (this can be rather fast in thin aluminum). A bit of chalk on the file might be helpful.

Also, electrical discharge machining can sink a graphite electrode of any shape (square or rectangular is easy) into metal. In mass production, that might be good (or you can make square dies this way, then punch it mechanically).

Reply to
whit3rd

The only rectangular ones which used to be available were the ones for the socket for the Potter & Brumfield 4PDT plug-in relays.

Or -- if you have a die filer, drill out near the border of the holes. then smooth to scribed lines on the die filer.

Good Luck, DoN.

Reply to
DoN. Nichols

I need to check to see if I can nibble as small as needed here -- the smaller holes I need is roughly half an inch on a side...

Reply to
Joe Pfeiffer

I skipped that because one mistake can ruin the panel.

I added some afterthought holes to the 3/16" thick control panel of a welded robot chassis by hand, since it was too big and obstructed by then for a machine tool. After four holes my hands were tired and less accurate; I wouldn't want to do 44.

If you take this route clamp the panel between boards to keep it steady and quieter. I use a coarse half round rasp to square up the hole if I can't saw it, then a "hand" file with a safe edge to cut to the scribed outline.

If you have trouble controlling the rasp, the thin edges are easy to grind 'safe'.

jsw

Reply to
Jim Wilkins

The nibblers I've see are about 1/8"-3/16" square so they should work fine.

Reply to
Pete C.

Nibbler.

Reply to
Michael A. Terrell

For the Adel Nibbler, to start it in the smallest hole, drill a hole which matches the diagonal of the square shank (punch), partially unscrew the stop screw at the other end, swing the lever arm out to allow withdrawing the punch, thread the small end of the punch through the hole and re-assemble the Nibbler to punch your way out to the outlines.

If you are even more space constrained -- drill a hole to clear the across-the-flats dimension of the punch, and file corners to allow it to be started.

If you want to cut slightly thicker aluminum than it is set up for, you can file a flat on the proper side of the stop screw -- at the expense of sore hand muscles sooner in the project. :-) (You didn't mention what *you* considered "reasonably thin" to be -- and opinions differ. :-)

If you are using an air-powered round Nibbler beware that the punchings are nasty crescents with sharp points on each end of the crescent.

And set up guides to follow so you don't wander outside the intended hole -- far to easy to do with the air nibblers.

Enjoy, DoN.

Reply to
DoN. Nichols

I've worn out quite a few bits and two Adel handles over the last 40 years. I currently have a cheapo hand nibbler I bought when no one had a new Adel in stock The design is different and has more leverage which is good for my Carpal Tunnel. I recently bought an air nibbler, but haven't tried it yet.

Reply to
Michael A. Terrell

Drill round, nibble and file to mark. HF DOES carry a pneumatic file, cheap at the half-off price. Where they nail you is with the file sets. It does work, I've used it on several projects where the amount of filing would be tedious. I have a square Greenlee punch, runs 1/2" square, though, and worth a lot more than the $5 I paid from the odd- tool closeout bin. Have never seen another except on paper and special order at that.

Could also use a micro-die grinder with an appropriate burr to square the hole a lot faster. Would leave less to file to square the corners out. I've used a carbide burr on steel panels for expanding a knockout for an off-center conduit, worked well, watch out for hot flying chips. Another old dodge is to drill the corners with a really small drill, then chew to that point with whatever and quit.

Stan

Reply to
stans4

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