Cutting sheet metal with a brake

Discussion in 'General Electronics Chat' started by spinnaker, Jan 1, 2010.

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  1. spinnaker

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    Oct 29, 2009
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    I had a friend tell me that sheet metal can be cut with a brake by first scribing it, then snapping it with a brake.

    Has anyone tried this?


    I don't mean to doubt my friend as he is one of these guys that can do just about anything, but I have done some searching and found nothing on this technique.

    I'm planning on buying a cheap brake from Harbor Freight and giving this a try but thought i would run it by here first.
     
  2. jpanhalt

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    Jan 18, 2008
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    That can be done with some of the heat-treated aluminum alloys, but I have never tried it with mild steel or SS. At best, I suspect you would get a rolled edge.

    What metal do you want to cut? Aluminum can be run through a table saw.

    John
     
  3. spinnaker

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    I just found one post on another forum suggesting it can be done but I do not have any details.

    It would probably be aluminum. I was thinking project boxes.

    I don't have a table saw. I was thinking of getting one but they take up so much room. I have also seen it being cut with a band saw.
     
  4. jpanhalt

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    You will find 2024T3 and 6061T6 as sheet in convenient thicknesses, like 0.032. The 2024 will break with a scribe; I am not sure of 6061, but it may too. The problem is that those alloys will not allow very sharp bends as you might want for your boxes. 3003 can be easily bent, but I doubt it shears easily using the scribe method.

    In other words, the requirements for making a box and for being able to use a scribe to cut the material are opposite. Good aviation shears can cut thin aluminum (say up to 0.040) without curling. Get a coarse mill or Vixon file for finishing the edges.

    John
     
  5. someonesdad

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    Jul 7, 2009
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    Woodworking tools can work OK for cutting aluminum -- I've used a chop saw, table saw, and band saw for cutting aluminum. It can require a bit of care, of course, but it can be done. A woodcutting blade on a band saw zips through 3/32" aluminum sheet quickly. A saber saw also works, but it tends to do coarser work.

    There are also ways to get things done with hand tools. For example, you can chain-drill and use a hand saw or hacksaw to cut sheet metal to size. Slow, but it works (also works on steel, brass, etc.). In a pinch, you can even use coarser saw blades (like a traditional carpenter's saw) -- the trick is to use shallow approach angles while sawing so that numerous teeth are also in contact with the metal (but only use these on aluminum or soft brass). It helps to put some lubricant on while cutting; almost anything works (even water), but the easiest is to probably have a spray can of WD-40 standing by. Paraffin also works -- I keep a chunk in my tool apron (it is also used for lubricating drywall and sheet metal screws before driving them into wood).

    By the way, when sawing, drilling, or cutting metals, it's virtually always advisable to use a lubricant. About the only times I don't are when cutting cast iron or free cutting brass. It's especially true when tapping anything. For tapping, my favorite lubricant is lard with about a quarter to third by volume of mineral oil (the amount depends on the temperature to get the desired viscosity). For small holes, I keep a syringe filled with the lard mixture (or some Vaseline) to squirt into the hole. I grind the sharp tips off the needles. I like 14 or 18 gauge needles; where I live, we can buy the needles and syringes from a local ag supply store.

    A key to doing this type of work is having a good workbench and a vise. Next to my measuring rule, the most important tools in the shop are the workbench and vise. If you don't have these, then make one or two sawhorses and use C clamps to hold the work for cutting.

    Finally, you have to have some good files to finish and deburr edges. I like my 12" Nicholson Magicut file with a big custom wood handle for working on aluminum.

    Added: my son-in-law was just over and he's an expert HVAC/sheet metal worker. He said he has a sliding device that is used to deepen a scribe mark on aluminum sheet. It's similar in concept to a tile cutter, which is also used for scribing. The cutter has one straight edge and one edge at about a 45 degree angle. You first scribe with a scratch awl, then deepen the scribe mark with the tool; he said it doesn't take very long at all. Then a quick snap breaks the aluminum sheet. He said it was about $60 when he bought it; I can't give you a brand name because he couldn't remember it. If I needed to make some boxes and stuff, this is definitely the tool I'd look into. He said his will help you cut up to about 24 inches of sheet.
     
    Last edited: Jan 2, 2010
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