The Home Machinist!

Hello, I'm new to this forum. I need help calculating the bend lines for a piece of 1/8" x 1 1/2" aluminum strip that I want to bend into a channel shape. The base of the channel needs to be 9 3/4" from the inside of each of the 2 legs. Also, each leg needs to be 3" long. The radius does not need to be too small/tight. So if the base of the channel will be 9 3/4" (inside dimensions) and the legs are 3" long, how long do I need to cut the the strip? I've seen formulas on other websites but I didn't understand them. I'm hoping that someone can just tell me how long the strip needs to be and where I need to bend to get the finished product. I apologize if this is hard to understand so feel free to shoot questions at me. Thanks for any assistance that you can provide.

I'm not able to provide the necessary dimensions, although I would if I could. I would like to make mention that without knowing the radius of the bend, no one will be able to provide the proper information, however. The radius determines the overall length, and will be a factor in where you should start your bend. The overall starting dimension will be shorter for a large radius than it would be for a tight radius.

One thing you should keep in mind. Sheet aluminum has grain, so if you're working with something like 6061-T6, it is prone to breaking if you make your bends parallel with the grain. The tighter the bend, the greater the chance it will break. Cross grain you should be fine, even with a fairly tight radius.

If the material you have is marked, the grain typically is parallel to the marking. If it isn't marked, you may be able to see the direction the material was rolled. It isn't always obvious.

Welcome to the forum!

Harold

Harold_V wrote:I'm not able to provide the necessary dimensions, although I would if I could. I would like to make mention that without knowing the radius of the bend, no one will be able to provide the proper information, however. The radius determines the overall length, and will be a factor in where you should start your bend. The overall starting dimension will be shorter for a large radius than it would be for a tight radius.

One thing you should keep in mind. Sheet aluminum has grain, so if you're working with something like 6061-T6, it is prone to breaking if you make your bends parallel with the grain. The tighter the bend, the greater the chance it will break. Cross grain you should be fine, even with a fairly tight radius.

If the material you have is marked, the grain typically is parallel to the marking. If it isn't marked, you may be able to see the direction the material was rolled. It isn't always obvious.

Welcome to the forum!

Harold

Thanks for the info, Harold. It sounds like I should be okay with the grain, as the grain is running lengthwise on the piece of alum. I'm thinking the radius should be .375. Hopefully this will help and someone can chime in with some dimensions if it's not too much trouble. I'm also going to check with a guy that teaches Welding at a local trade school, and he has access to a brake press. He should be able to lend some advice/assistance. Thanks again, Harold.

Here's a bend allowance chart, for 90 degree bends.
Let me know if you have a question.

Bill

Harold_V wrote:One thing you should keep in mind. Sheet aluminum has grain, so if you're working with something like 6061-T6, it is prone to breaking if you make your bends parallel with the grain. The tighter the bend, the greater the chance it will break. Cross grain you should be fine, even with a fairly tight radius.

Steel has grain as well, as do all metals, although it is rarely an issue with steel but thought it worth mentioning. I have worked with hot rolled steel flat bar (it was either w44 or a36 I can't remember which now) that when bent lengthwise fractured. The same as Harold described with aluminum.

Thanks for the info guys. Bill, thanks for posting the link for the chart. Good stuff. Looks like I should add 0.6676 per 90 degree bend since my material is 1/8" and the radius is .375?

redneckalbertan wrote: Steel has grain as well, as do all metals, although it is rarely an issue with steel but thought it worth mentioning.

Well worth mentioning!
I have seen several failures in heavy equipment chassis', buckets, etc, because bends were made with the grain. More severe the tighter the radius.
I've seen plate fail in brakes while forming, most notably harder steels & alloys like AR plate, but even AR572. Downright scary....and dangerous.

For any parts where it was at all important, and especially critical, the direction of grain was noted on the drawing.

Bill

Mark M wrote:Thanks for the info guys. Bill, thanks for posting the link for the chart. Good stuff. Looks like I should add 0.6676 per 90 degree bend since my material is 1/8" and the radius is .375?

You got it!

Handy old chart from a place I worked years ago. Makes it easy to make your flat pattern.


Bill

Thanks!

Hope I didn't miss the answer, but the formula I always used is Radius plus 1\3 of metal x 1.57 for a 90 degree bend (1.57 =Pi Divide by 2).