How to cut a rectangular hole, smaller than 1", in sheet aluminum?

[johnyradio]

Hello

We are a non-profit electronics mentoring project for at-risk youths.

We need an inexpensive, portable, quick method to cut, drill, or punch a clean rectangular hole in 0.012” (30 gage) aluminum sheet.

we are going into production, so we need something quick and consistent.

We do everything by hand, and each builder is an independent craftsperson, so each builder needs their own personal toolset. So it can't be too expensive.

We can only use hand-tools (electric or manual), or inexpensive benchtop or table tools (about $50 max, but $25 seems more reasonable to cut a hole in aluminum!). The method should lend itself to other size/shape holes. Modifying or repurposing off-the-shelf tools is fine, tho.

Here's the piece. It's something like a gas pipe or chimney pipe cap from a plumbing supply company.


The rectangle hole needed is approx 1/3" x 2/3", and it must fit the following part (JUST the trapezoidal section with little holes in it, not the entire part):



I've found a few methods, need feedback/suggestions:

• Buncha holes: The old "drill a bunch of holes in a row" method. Not accurate, not clean, not professional-looking. We could clean it up with a file, but too time-consuming, and still not very accurate.
• Nibbler: Drill holes in the corners, then use a nibbler. Seems only slightly better than the above method. Concerned about curls/distortions and burrs in the metal. However, if someone knows a tool and technique that will give us consistent results, please share! Do nibblers give clean, straight tiny cuts, without curling or messy edges? One guy says "Nibblers are punches- they punch a series of overlapping round holes. They leave behind a pile of razor sharp miniature half moons that stick to shoe soles, flesh, socks, wood, pretty much everything. They do not cut straight lines very well. Freehand, you usually a get a slightly serrated looking edge. Used up against a clamped down fence, they are a bit better, but still not shear quality." If that's true, forget nibblers.
  Precision Hand Shear Sheet Metal Snips Nibbler Cutter Cutting Tool Cut Modify | eBay
• Metal snips or metal shears, ditto above.
• Metal file: I don't mind a quick file to smooth sharp edges, but to cut the whole hole with a file is too time-consuming and labor-intensive, and not accurate.
• Arbor punch press. This seems promising. My idea is to get a standard 1/3" square punch, and then punch two holes side-by-side, to get my desired 1/3" x 2/3" rectangle-- but that could produce a crooked rectangle if the squares are not lined up. Does thin aluminum really need a 1/2 ton or more of pressure?
  1 2 Ton Arbor Press | eBay
• Hammer: I understand the punch and die used on the punching machines can be used by hand, with a hammer, without the machine. Anyone have experience with that?
• Hand-punching tool. I'm very interested in this method, as it seems simple, quick, and consistent. But have not yet found a hand-punch with square punches. Anyone? Do these things hold any size punch, from any manufacturer, like a drill can hold any size bit? Trick-tools tells me "all square sizes will be $173 each."
  Grizzly.com
  http://www.trick-tools.com/XX_Hand_P...9#.UqtktPRDuSo
• 2 Inch hand hydraulic metal hole punch press?
  2 Inch Hand Hydraulic Metal Hole Punch Press - Buy Hydraulic Metal Hole Punch,Hand Hydraulic Press,Hydraulic Punch Driver Product on Alibaba.com
• Dremel or similar tool?
• Square punches for wood. Wood these work on 30 gage aluminum? The retailer says "These Punches are hardened to RC48 which should be harder than your aluminum so yes it should work. The question will be the durability and how long it will stand up and it will probably need more frequent sharpening than using this on wood as it was intended."
  Square Hole Punches - Lee Valley Tools
• Screw-down: Not invented? I've heard of a punch that you just tighten until it punches thru, but have not found any. i imagine drilling a small round hole in my aluminum sheet, then fitting two small separate hardwares on either side of the sheet, screwed to each other through the small round hole. They are some kind of punch and die. Then, tighten them down, and out pops the square hole in my sheet. Does this exist? If not, let's invent it!
  Q Max Square Sheet Metal Punch 19mm | eBay
• Straight-line punch? Something like a chisel. With a hammer, cut each side of the square hole. Seems promising, yet risk of inaccuracy.
• Big round punches + corner punch: Round punches a very inexpensive, so punch 3 large 1/3" holes next to each other, overlapping. The corners would be round, so maybe a corner punch could help
  http://www.micromark.com/SearchResul...e=corner+punch
• Fret saw. Also seems promising, tho not quite as quick as a punch. Can be extremely accurate, but only as accurate as the user. They are cutting copper in the vid, would it work with aluminum? Would love a throatless, or electric, or deep-throated version of this, for installing parts not near the edge. Anyone?
  Knew Concepts 3" Fret Saw Frame - Fine Metalsmithing Saws Designed for Artisans - The Red Saw - Santa Cruz, CA
  Art Jewelry - Basic Metal Piercing Techniques - YouTube
• Something else?

Many thanks!

John Weiss, Director
Bayview BOOM Mentoring Project
bayviewboom.org
415-68-WHEEL

We teach teens in the hood how to build boomboxes. This is a violence-reduction program, and much more. Check out this fun 2-minute video of some of our participants: