Bending metal

[Curtis Nelson]

I haven't decided yet between brass and aluminium, but I do know that I need to bend some 1/2" x 1/8" metal to form the front standard of my camera (it will be 'U' shaped, ideally with 90 degree corners). What kind of brass or aluminium should I shop for, and what's the best way to bend it? Keep in mind that I also need to cut slots in the sides, so machinability is also a consideration.

Thanks,

Curtis

 

[Dave Parker]

The best way is of course if you can gain access to a metal break, which will give you good clean bends, you can also use a vise with soft jaws and a leather mallet with wood breaks to attain good clean bends, which will take a bit longer to produce the clean bends you will need, but can be done pretty easely, good bar stock brass in the size you will use is pretty easy to find, I picked some up at the local true value hardware store, but most hobby shops also carry a selection of brass stock.

Dave

 

[noseoil]

Curtis, try a couple of different types, but I've found the garden variety hobby shop brass to work well. Aluminum may or may not do what you need, but it depends entirely on the stock. See what's available in your area and find out how it works is the best I can do.

To get 90 degree corners, set up a couple of blocks and a vise. Use a radiused corner on one block to form the bends. Make sure to keep the legs parallel in both planes. You will have to decide if milling the slots is easier before or after the bending is done. Figure on doing a couple of tries until it is just right. tim

 

[jjstafford]

My preference would be steel because it can be heated, bent nicely and tempered. That's tricky with aluminum. I second the tip to use a break - with heat. I've found it worthwhile to draw up what I want and then have a pro do the metal work. It's cheaper than buying all I need to make specialparts.

 

[waynecrider]

You can consider having it done by sheet metal shop and it would be fairly inexpensive. They'll probably have a small brake to do it with which is a must, and a good mechanic should be able to get your measurements. The problem is getting both (shall we say) vertical sides equal, which is a feat in itself. You might consider trying to buy some channel. This would be a much better way to go, as the channel would be formed thru a die and not a bend.

The sheet metal shops I have dealt with usually don't carry brass, in which case they will probably let you supply the materials. If a mistake is made tho, thry will more then likely not accept responsibility for the materials. Bending metal exactly as you need is an art unto itself. I know having worked as a sheet metal mechanic. Also consider a front standard off a parts camera.

 

[Jim Chinn]

If you go with aluminum you have to consider the alloy being used. 6061 is a non-bendable, more brittle alloy that is primarily used for structural applications. It can flex some but will not hold a bend and at a specific load point it will break. 6061 machines better, cuts cleaner, holds threads better but is more difficult to machine then 3003.

3003 is considered an aluminum alloy for forming and thus can be bent at angles in a metal break machine, worked on an english wheel and bead rolled. it is much easier to machine if using hand tools such as a dremel style cutter and hand files.

The problem with 3003 is that it is not nearly as structuraly stiff as 6061, and thus for example a 2" wide .125 piece of 3003 bent at a 90degree angle will not have the rigidity of 2 peices of .125 6061 welded and reinforced to make the same angle. However rolling a bead will substaintially add to stiffness.


6061 can be heat treated and annealed, which provides the ability for forming but it will loose a certain amount of strength at the point of any bend.

There are more exotic alloys with different characteristics. 5052/51, 7071, 3035, but these are more expensive and not as common and really provide no advantages for simple applications such as a camera.

Ideally for something small like 4x5 or 5x7 you could use stainless steel. But you would really want a machine shop to slit it to size, and machine holes and slots. Proabably about a $100 to $125 job.

If you are working with small dimensions, for say a 4x5 (6" between uprights and say 8" uprights on each side) and choose aluminum, you should be able to find everything you need at an Ace, True Value or Home Depot. They all have a selection of aluminum flat, angle and channel in thcknesses of .063 and .125 and usually from 1/2 inch widths on single sides up to 2". The angle and channel are usually 6061 and the flat is 3003 or similar.

With aluminum, drill and cut any holes or slots before bending. If you are making a simple slot for say the shift and swing on a front standard, mark a center line, center punch a series of holes, drill and finish the slot with some sharp files or a dremel type tool. A machine shop will cut a slot for you but will charge you at least $50-$60 or what ever their hour minimum is.

I could provide you with more specific suggestions if I knew the demensions of the pieces you need to make.

 

[Curtis Nelson]

Thanks for the great responses. I'm actually building an 8x10 camera, but the dimensions Jim mention (8" uprights, ~6" between uprights) are pretty close to what I need.

Thanks again. More input is welcome.

 

[smieglitz]

For brass U-channel stock try http://www.mcmaster.com/
and go to catalog page 3438 or 3440. I'm sure they would have an even wider selection of aluminum.

I recently tried to bend some 1/8" brass sheet stock on a break for the first time and it essentially ripped. I decided to order some angle stock after that attempt.

Joe

 

[Donald Qualls]

I'd recommend brass over aluminum. Brass can be annealed easily by heating it to red heat and quenching in cold water; it can be soldered very readily with silver-bearing solders that are nearly as strong as the metal, cuts and drills nicely with common metal working equipment and doesn't clog grindstones and files as badly as aluminum, and IMO looks nicer than aluminum (which to my eye gets gray and ugly as it ages). Brass repolishes better and isn't prone to galling as most aluminum alloys are. Brass comes in a number of useful rolled and extruded shapes (round, square, and hex tubes, angles and channels, as well as strips and sheets), available in small pieces at somewhat reasonable prices -- many more such than aluminum, from which extrusions are typically available only in shapes and lengths suitable for making screen doors and such.

It is important to anneal brass before trying to bend it; most stock purchased off the shelf will be work hardened from being cold rolled and thus prone to split when worked further. Just heat the stuff up to dull red heat (don't go much higher, though, or keep it hot too long; the metal melts just above red heat and you'll slowly drive off zinc from the brass even at a dull red), then drop it in cold water. To reharden later, if needed, heat the brass red hot and allow it to air cool.

 

[Aggie]

brass doesn't need the air cool to harden, it is non ferrous and thus is hardened by work. You anneal the metal to soften it. to harden it when it is non ferrous is to actually hammer bend or other wise mash it. You can also sand blast it to harden it. Just heating non ferrous again, makes it soft, and that is not what you want. To clean it after you have worked it, get a small pot and some strong vinegar, and let the pieces sit in hot (just about boiling) vinegar. This will work in a pinch as a type of pickle. If you have access to swimming pool acid that is even better. Pickling metal cleans it of any surface impurities that you get from annealing and working it. For those times between annealing and working, just use a spray like 409 (kitchen spray cleaner) to de grease the metal. I would go with either an 18 guage or smaller size. In metals decending numbers means thicker metal.personally I would be working with some of my old 14 guage, then if I needed too, I could smash it thinner to work harden it.

 

[jjstafford]

brass doesn't need the air cool to harden, it is non ferrous and thus is hardened by work. You anneal the metal to soften it. to harden it when it is non ferrous is to actually hammer bend or other wise mash it. You can also sand blast it to harden it.

Sandblasting, or better - glass bead blasting, treats the surface, so for trying to avoid fractures which start at the surface, it is good. We first learned this by accident racing cars in the fifties when we sandblasted valve springs just to clean them and then they mysterously stopped breaking on the track. Now glass or media blasting is routine.

 

[Charles Webb]

I am jumping in simply to re-enforce Aggie's comments, they are dead on correct.

 

[jjstafford]

I am jumping in simply to re-enforce Aggie's comments, they are dead on correct.

Regardless of the question as to whether brass for a front standard is a good idea. From my experience, it seems to be a poor choice.

 

[Curtis Nelson]

So let me see if I've got this right: If I choose brass, to bend it, I just need to hit it with the 'ol propane torch until it just starts turning red, at which point I can bend it into the shape I need. When finished, I don't want to stick it in cold water; rather, I want to boil it in vineagar for a few minutes?

Thanks for the help

Curtis

 

[Aggie]

you don't have to heat itin hot vinegar, that bath called a pickle is used to clean the junk that coats the surface when you anneal and work with it. Until you work with it, you don't really understand how dirt and encrusted with gunk it can get.

BTW there are different grades of brass. Some are quite a bit stronger than others. I'll look up my old supplier. The stuff in hobby shops is the softer version because it is easier to use by the general public.

This company sells small sheets of brass. The ones i use to work with are 4' x 6' I doubt you will need that much. Otto Frei, is located near me, and the people very friendly. They might even carry 14 guage if you ask them.

http://www.ottofrei.com/store/product.php?productid=7399

 

[AlanC]

Curtis,
If I were you I would re-think the design of your front standard. I used a similar design on the first 5 x 4 camera I made, but instead of 0.5 inch wide aluminium I used 2 inch wide stock. Even so, the finished result was nowhere near rigid enough. I cut a slot in the base of the U, to give me cross slide, and this weakened the design so much you could rock the front of the camera back and forewards with only moderate pressure. Making a lens cap exposure could cause it to move...
For a 10 x 8 camera I would try to come up with something more rigid.
Alan Clark

 

[MenacingTourist]

Curtis,

Let me know if you need any help with this project. I live down the road from you in Springville and know a couple of metal fabricators, one of which owes me lots of favors. But mostly I want to help because this project sounds like a lot of fun.

Alan.