It Came From the Fab Shop: Tools Even Better Than HammersBy Loren Krussow Posted 05/11/09
If you're anything like me, the first time you took a hammer to a piece of sheetmetal intending to make something out of it you were a little miffed at the result. On one hand you might have been impressed with the way you might get a useful part out of a straight sheet, on the other hand...wow did it look awful. It's safe to say that many people give it another try or two and then join the ranks of those who believe that metal forming is a black art and not for them.
As much as you can do magic with a few well-placed hammer blows, you can also make a ruinous mess. Stretching is the first thing that happens to metal when hit with the impact of a hammer, and the repeated impacts that may be required to get a bend to "come around" are likely to create enough distortion that you may need to come back with lots of additional hammer work to straighten things out. Or a grinder and some filler may be involved.
What is really best when forming sheetmetal is a smooth, even pushing action across the bend, not an isolated impact, and this is where more specialized tools come in. At the most basic, you can clamp a piece of sheet into a vice and place a block of wood on the exposed section, then hit the wood with a hammer to get a more even force across the bend. Better yet is to have access to an actual sheetmetal bending tool called a hand brake, which in effect does the same thing: a portion of the sheet is clamped between two plates, then an additional bar swings up to push on the material and bend it over the edge of the upper plate. These useful and relatively inexpensive devices can vary from a bench-top model which weighs a few pounds or a ten-foot-long floor unit weighing a ton, but all are hand-operated via levers.
For production work and where greater precision is required, a better answer is to have a powered "press brake" version of an industrial press, with a long bed and an upper jaw into which forming dies can be clamped, then squeezed together by mechanical or hydraulic means. These devices are used around the world for bending of things like electronics chassis and cabinet doors, can bend heavier plate, and are extremely versatile if a bit expensive. And they bite! Only skilled and careful operators need apply...before the days of safety emphasis, it was common for older guys to be missing a finger-or-two as a reminder of the day they showed up to work with a less-than-optimum attention level.
When my machinery dealer called to say a medium-sized, used press brake had come in and he could get me lease-to-own terms, I was both happy and apprehensive. I wanted it bad but would be risking that I could get enough contract work to pay for it. As it happens, things worked out and it's been a favorite machine ever since. I've probably run tens of thousands of cycles on it and it's never skipped a beat. You can imagine that I've formed plenty of my own (and friend's) car parts such as the steering box relocation bracket shown, as well as paying jobs. With 45 tons of force available, I have also never argued with it.
We still get out the ol’ hammers often enough however, even with the press brake around they are never lonely for long.
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Written by NMCA_Ron
May 16 2009
If you go to Wilson Tool's website, you can get the dimensions of the tooling (punches and dies) for American and European style press brakes. This stuff is pretty standard and can be found on evilBay and Craigslist on a regular basis as many fab shops and sheetmetal companies will discard old tooling as it becomes too worn to hold tight production tolerances. This tooling is still great for backyard use and can be bought for a mere fraction of the original price.
After reviewing the size and shape of the tooling Wilson offers, you can construct a tool holder for the punch and attach it to the ram end of your press. You will probably need a torch or plasma cutter to cut out the pieces for this tool holder and a welder to put them together, but it will pay off in the long run. You will then need to make a pedestal to mount the dies on. This will be a plate about 1/2" thick. Float the die on this mount and slowly bring the punch down into it to where it zeros out on the die. Scribe a line around the base of the die to mark its location on the pedestal. and raise the punch. You can then either drill and tap the pedestal to secure the die or form some type of holder bracket, like angle iron, to locate the die on the pedestal.
When using this type of tooling, remember the die opening must be at least 5 times the material thickness you wish to bend. Example: if you are bending 1/8" thick material, you will need a die with a V-opening of at least 5/8". This will keep the tooling from breaking due to too much pressure.
Here are some pics of typical pressbrake tooling.
[img]http://www.ohknife.com/pictures/cnc_sharpening/press_brake_dies.jpg[/img]
[img]http://www.westbrook-eng.com/images/new/Open%20House%202009/Wila-Tooling.jpg[/img]
Ron
Written by kso4
May 13 2009
I can post some pics of homemade ones in the next few days...
Written by BigBlockRanger
May 13 2009
[quote author=Weldangrind link=topic=12128.msg237350#msg237350 date=1242089997]
but I'd pay for a selection of jaws and adapters that are designed for a small press. Has anybody seen such things?
[/quote]
x2
Written by realsteelfreak
May 13 2009
Well good I like the BS site,and its nice being on here with good people. I must have had one to many to drink while looking over stuff and somehow thought Loren said Brian, well you know what I mean, just one to many.
So nice job Loren!!!
Written by Brian Lohnes
May 12 2009
Hell no, I LOVE getting credit for good stories! :)
Brian
Written by realsteelfreak
May 12 2009
My bad, do I have to go to timeout now?
Written by TheSilverBuick
May 12 2009
[quote author=realsteelfreak link=topic=12128.msg237512#msg237512 date=1242099563]
Nice article Brian, My next tool to be purchased will be a decent quailty 48'' hand brake . I like that press brake though!
[/quote]
Nice write up Loren ;) Those things are awesome machines, especially with that heavy gauge steel. I just got a hammer, a concrete floor, a concrete step and a few pieces of wood to work with :P I've never made any thing successfully with them :P
Written by NMCA_Ron
May 12 2009
Press brakes rule! I operate one from time to time at work (Old, old OLD Amada) and I gotta tell you, they are quite handy to have around. We bend everything from 18 ga. cold rolled A36 sheet to 1/2" plate. I agree, you absolutely, positively need to have your wits about you when you operate one of these machines. Not only can you lose a finger, but if you do not set up the tooling correctly, you can break a punch or die and send pieces of jagged, hardened steel whizzing across the room. Ask me how I know... ::)
Ron
Written by stoneshrink
May 12 2009
ah the good old days... My dad has a 12' press brake, 10' shear, and a pullmax.... someday, I suppose, those will be mine and my wife will wonder (like my mom) at why I have it. I'll be sure to show her this article :)
Written by Matt Cramer May 16 2009
[quote author=NMCA_Ron link=topic=12128.msg237658#msg237658 date=1242125560]
Press brakes rule! I operate one from time to time at work (Old, old OLD Amada) and I gotta tell you, they are quite handy to have around. We bend everything from 18 ga. cold rolled A36 sheet to 1/2" plate. I agree, you absolutely, positively need to have your wits about you when you operate one of these machines. Not only can you lose a finger, but if you do not set up the tooling correctly, you can break a punch or die and send pieces of jagged, hardened steel whizzing across the room. Ask me how I know... ::)
Ron
[/quote]
I used to work for Amada - wasn't in the press brake division, though. Heard a few interesting shop accident stories there, though.
When I designed the MSPNP cases at work, I designed them around making them easy to form on a press brake, since they were a bit of tooling I was familiar with. That, and we didn't want to tool up for custom made extrusions for a short run of cases.