Question on bending metal on a brake...

[jtrom]

I need to bend many steel and aluminum fittings, brackets, bellcranks, ect. for a wooden plane project. The thickness is anywhere from .050 to .125. I am thinking about buying an inexpensive brake that can handle these thicknesses. I know the thicker the material, the bigger the bend radius needs to be. How do I change the bend radius on a brake when using different material thicknesses? Maybe I am confused on the bend radius. I thought the radius was formed my bending the sheet metal around something of the specific size that you need. How does this work on a brake when everything is fixed?

[martymayes]

On some leaf brakes, the radius can be somewhat controlled in the setup with set back. When bending thin material, a radius former is usually used. I usually just bend thinner sheets to get the desired radius then bend my part. You won't be bending anything much thicker than .040 on a cheap...er, I mean inexpensive brake. If you plan on bending 1/8" thick material on a leaf brake it will take a heavy duty and expensive machine. That type stuff is better worked in a press brake. Most likely for the thicker parts you need you can bend it with forming blocks, vice and a hammer.

[WLIU]

I will second the notion that you will want to use a tool that looks like a press brake for being the thicker material. I will suggest though that a hammer and the associated percussion is not needed. You can purchase an inexpensive press that is a steel frame with a hydraulic jack mounted upside down in it to provide the muscle to push your male "V" block down on your part to press it into the female "V" block to make the bend. We can leave as an exercise for the reader how to make the V blocks for the press. Really hard wood (rock maple?) or steel works for those.

Best of luck,

Wes
N78PS

[Frank Giger]

Actually, a good ole Harbor Freight bending brake will work for smaller (in total size) aluminum pieces of that thickness.

The question of how to know how far to bend is both simple and difficult - bend slightly past the desired angle and then let it come back.

For 90 and greater bends, do it in two 45 degrees - bend it about 50 degrees, stop, let it spring back. Then edge the piece back a bit from the bending point (um, an eighth of an inch or a little less) and then bend again.

With some practice you can get very precise - I did a 14 degree bend through very careful bends and checks on a thick aluminum gusset:

http://www.darts-page.com/images/Nieuport/cab024.jpg

Here it is laying on my el cheapo Harbor Frieght bending brake:

http://www.darts-page.com/images/Nieuport/cab026.jpg

In the latter pic, you can see the bending brake is basically two pieces of steel on a hinge setup with a flat piece of steel that sits on it. What one does is lay what one wants to bend flat on it, put the flat piece on top of it, leaving a little space (um, the thickness of the piece plus a tad), and then clamps it in place onto the brake.

Then grab the handles and pull towards one's self.

Hope this answers your question.

[prasmussen]

I need to bend many steel and aluminum fittings, brackets, bellcranks, ect. for a wooden plane project. The thickness is anywhere from .050 to .125. I am thinking about buying an inexpensive brake that can handle these thicknesses. I know the thicker the material, the bigger the bend radius needs to be. How do I change the bend radius on a brake when using different material thicknesses? Maybe I am confused on the bend radius. I thought the radius was formed my bending the sheet metal around something of the specific size that you need. How does this work on a brake when everything is fixed?Bending is deceptively simple. The reason to bend on a radius is to avoid cracking the outside of the bend of course. And so much depends on the alloy of aluminum or steel. Calculating bending allowance is something I attempt to avoid by bending first and fine trimming a part after when possible. The Aircraft Mechanic's Pocket Manual, Metalworking in the Home Shop and a really dated book titled How to Do Aircraft Sheet Metal Work are what I refer to. Best of luck!

[jtrom]

Actually, a good ole Harbor Freight bending brake will work for smaller (in total size) aluminum pieces of that thickness.The question of how to know how far to bend is both simple and difficult - bend slightly past the desired angle and then let it come back.For 90 and greater bends, do it in two 45 degrees - bend it about 50 degrees, stop, let it spring back. Then edge the piece back a bit from the bending point (um, an eighth of an inch or a little less) and then bend again.With some practice you can get very precise - I did a 14 degree bend through very careful bends and checks on a thick aluminum gusset:http://www.darts-page.com/images/Nieuport/cab024.jpgHere it is laying on my el cheapo Harbor Frieght http://www.darts-page.com/images/Nieuport/cab026.jpgIn the latter pic, you can see the bending brake is basically two pieces of steel on a hinge setup with a flat piece of steel that sits on it. What one does is lay what one wants to bend flat on it, put the flat piece on top of it, leaving a little space (um, the thickness of the piece plus a tad), and then clamps it in place onto the brake.Then grab the handles and pull towards one's self.Hope this answers your question. Can you do multiple bends on that brake?....like a joggle for a bell crank?

[Frank Giger]

I've done tight U channels out of flat stock, as well as some S bends on that brake. The big thing is the length of the brake - it one can't fit onto the plate it's a no-go.

[Ted1491]

http://www.precisionsheetmetal.com/home/materials.htm

Alum has a grain, if you bend with it it will crack, always bend across the grain, rule of thumb is the bend radi is 2 times the material thickness (1/8 = .125 x 2 = 1/4"r) up to 3/32", then it's 4x,,you can go tighter on the R depending on what the Alum is, a simple brake can be made using a 2 or more ton Hyd jack and some ingenuity.