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Author Topic: Home Brewing with Sheet Metal  (Read 8889 times)
ND9B
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« on: December 28, 2011, 03:02:24 PM »

I would like to make my own custom chassis and enclosures up to around 18" on a side. What tools do I need to do a good job? (I take it that I'll need a brake and shear.) I see Eastwood has an inexpensive 18" brake. It looks like the sheet metal is held down by a "bar" with C-clamps during the bending process. This does not look like it would allow bends on adjacent edges. Can this be remedied by a short "bar" that fits between the bends on opposite edges?

Now, what about cutting the sheetmetal? I have a saber saw that can cut sheetmetal, but it would make for a ragged, wavy, ugly edge! What do I need to make a nice, straight, clean edge?

ND9B
« Last Edit: December 28, 2011, 05:48:46 PM by ND9B » Logged
AA4PB
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« Reply #1 on: December 28, 2011, 03:59:21 PM »

What you need is a straight shear to make the long cuts and a notch shear to take out the corners for bending. Then you need a pan and box brake to make the bends. A pan and box brake has removable clamps so that you can have openings to clear the sides as you fold the metal upward.

The bottom line is that you need a lot higher quality (read expensive) equipment than one of those inexpensive brakes if you want to do a professional job. You'd have to make a lot of boxes/chassis/enclosures to make the equipment to do it youself pay as compared to purchasing ready made stuff from a supplier.
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ND9B
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« Reply #2 on: December 28, 2011, 05:57:47 PM »


The bottom line is that you need a lot higher quality (read expensive) equipment than one of those inexpensive brakes if you want to do a professional job. You'd have to make a lot of boxes/chassis/enclosures to make the equipment to do it youself pay as compared to purchasing ready made stuff from a supplier.


Who's a supplier of boxes/chassis/enclosures? I used to buy that kind of stuff at hamfests, but can't find them anymore.

ND9B
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AC5UP
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« Reply #3 on: December 28, 2011, 06:14:28 PM »

http://hammondmfg.com/
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KA4POL
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« Reply #4 on: December 28, 2011, 10:52:37 PM »

I can understand easily that in view of high prices for enclosures you are tempted to go DIY. My way is to go to a nearby machine shop. They got professional equipment which I could never put to cost effective use. Forget wasting your money on unprofessional tooling. Of course ready made enclosures are also a good but sometimes costly way for your homebrew equipment.
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G3RZP
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« Reply #5 on: December 29, 2011, 05:08:25 AM »

A bending brake with slots in the bars allows you to make a limited number of 4 sided boxes. If there is room for a 1/2 inch bar, you can even do an inside flange. I have a cheap ($50) Japanese one that does up to about 19 inch wide material that you can do inside flanges with. It's worth while soldering or welding up the seams - there's a guy in the flea market at Dayton each year selling really good stuff for that.

There's no real replacement for a shear. Mine takes up to 1/16 inch steel, with a width up to 39 inches. Big, new Chinese, heavy and was around $300 ten years ago. Massively dangerous - no guard to stop your finger going into the blade, and no guard to stop the pedal coming down and smashing your foot. Both easily fixed with a length of 1 by 1 angle steel and a length of 2 by 4 wood. Ypou can cut PC board material on it too, although much use on fibreglass will blunt it.

I don't have a notch shear, relying on a nibbler, files and even the milling machine.

A trick from old ARRL handbooks for cutting sheet metal. Score deeply on both sides, clamp between a couple of pieces of angle steel or even hardwood in the vice such that you can bend the sheet backwards and forwards along the scored line until it breaks. To clean up the edge (and this should work with the saw), lay a piece of emery cloth on the bench and run the rough edge of the sheet backwards and forwards across it.
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ND9B
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« Reply #6 on: December 29, 2011, 06:11:27 AM »


A trick from old ARRL handbooks for cutting sheet metal. Score deeply on both sides, clamp between a couple of pieces of angle steel or even hardwood in the vice such that you can bend the sheet backwards and forwards along the scored line until it breaks. To clean up the edge (and this should work with the saw), lay a piece of emery cloth on the bench and run the rough edge of the sheet backwards and forwards across it.

What would you use to score the sheet metal? (I'm a bit mechanically challenged.)

Also, are these hand held electric shears (that cut out a thin strip) any good? Can they cut a resonably straight line?

ND9B
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TANAKASAN
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« Reply #7 on: December 29, 2011, 06:40:42 AM »

Score aluminum on the inside only with a nice deep cut and you can make nice neat bends without a brake.

Tanakasan
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K1ZJH
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« Reply #8 on: December 29, 2011, 06:56:21 AM »

http://www.k3iwk.net/

k3iwk makes a line of chassis's and enclosures and does custom work.

I've been looking at the Harbor Freight combo brake/sheer; but I'm not sure I could justify the
cost or whether it is worth buying.

Pete
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AA4PB
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« Reply #9 on: December 29, 2011, 08:23:27 AM »

Who's a supplier of boxes/chassis/enclosures?

Mouser Electronics (www.mouser.com)
DigiKey Electronics (www.digikey.com)
Allied Electronics

Try a Google search - there are lots of dealers that supply products from Hammond, Bud, and others.
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K8AXW
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« Reply #10 on: December 29, 2011, 09:16:22 AM »

I've been homebrewing for over 40 years and there are two areas that have caused a great amount of grief.  One is front panel finish and labling.  The other is the sheet metal work.  Unfortunately, I didn't have inexpensive equipment available to me in the early days and in the later days when it was available I couldn't justify buying it.

With that being said, I would advise staying away from the cheap import shears and brakes.  They simply won't give you the performance you need.

I would advise looking around and checking the phone book Yellow Pages for small shops that might be willing to make your bends for a reasonable price. 

However, if you do locate one, you should have your metal laid out with machinist bluing and the 'cut' lines scribed onto the metal and the bend lines marked with black felt pen.

If your new found shop has a notching machine, great.  If not then have him cut the sheet metal, take it back to your place and cut the notches with a hacksaw and finish the notch edges with files. (rough and finish files)  Then take it back for the bends.

If your machinist knows anything at all he'll know how to make the bends in the correct order.

(All of this might help you save money)
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G3RZP
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« Reply #11 on: December 29, 2011, 09:19:25 AM »

Score the aluminium with a knife or even a good scriber. I don't know about hand held electric shears: straight old fashioned ones (we call them 'tinsnips') have some problems with the metal bending. I have a mechanical nibbler which attaches to the electric drill: I find it a bit fierce and hard to keep a really straight line cut, but if you are careful, you can cut oversize and clean up with tinsnips.

We have things called Abrafiles which are good for cutting holes. These are round saw blades, about 1/16 in diameter, which have some clips to make them fit a hacksaw.

If you want to use a jigsaw, clamp a piece of wood (or angle steel) with G clamps so that you have a solid rest against which to hold the tool: that will help you get a straight line.

A lot depends on how much you're going to build, how much money and effort you want to put into it, and if you are likely to get other hobbies (such as model engineering) where the same tools are useful.

A few other tips: cheap tools are not generally worthwhile unless they will get very limited use. Engineer's combination squares if cheap may be a long way off 90 degrees. Get good quality drills (Sears do them) and files. Some aluminium is hard and won't bend without cracking. In that case, rub some soap on it and heat the other side with a blowtorch until the soap turns brown, and then let it cool. The aluminium will have annealed soft, and may well harden over the following month or two. That's useful for dealing with bent beam antenna elements.

It seems K8AXW has been saying a lot of the same stuff while I've been typing. Engineers blue is very useful, but you want also a bottle of methanol to clean it off - and note that methanol is very flammable, so keep it away from the blowtorch!

My workshop is pretty complete, with a lathe, a shear, a brake, a small brazing hearth, a grindstone, a drill press and milling machine. They make home brew metal work much easier...although there are times that a power hacksaw would be desirable.

A load of good testgear is useful too.

Hope this helps

73 es HNY

Peter G3RZP
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WA2ONH
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« Reply #12 on: December 29, 2011, 12:00:41 PM »

TenTec makes other items besides Ham rigs...

See there Enclosures at:

LINK: http://www.tentec.com/categories/Enclosures/

Good luck. Happy New Year!
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73 de WA2ONH dit dit    ...Charlie
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"No time is ever wasted that is spent LEARNING something!"
W7ETA
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« Reply #13 on: December 29, 2011, 12:43:23 PM »

I seem to remember that the ARRL Hand Books from either the 40s or 50s had suggestions for sheet metal projects.

HVAC companies might still have equipment for sheet metal work?

73
Bob
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K8AXW
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« Reply #14 on: December 30, 2011, 08:19:11 PM »

Quote
Engineers blue is very useful, but you want also a bottle of methanol to clean it off - and note that methanol is very flammable, so keep it away from the blowtorch!


On this item:  This mechanics layout blue (or green) can be bought at McMaster-Carr and it's fairly inexpensive.  I used a pint bottle for years.  When it finally ran out I could no longer justify buying another bottle so now I use a heavy felt pen. 

When finished I clean either the layout blue or the felt tip pen ink off with Acetone which is available at any hardware store.  The "flamable" caution still holds!

I have a 5" vise that I use in many cases to cut aluminum with a hacksaw, slightly larger than needed and cut it down to the scribe marks with files.  OK, that's a PITA but again sometimes a small project can be done without spending money on having someone cut it for me. 

However, when it comes to bending I have it done on a brake.  Doing the layout, cutting and notching will save you a lot of money.
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