Simple box forming question?

Sheet Metal Fabrication techniques, questions and help. "Tricks of the Trade"

Moderators: Harold_V, GlennW

Post Reply
mcman56
Posts: 156
Joined: Thu Apr 17, 2003 2:30 pm
Location: Roseville, CA

Simple box forming question?

Post by mcman56 » Wed Oct 15, 2003 2:40 pm

I need to form an Aluminium box to cover a motor. It needs three sides (left, right and top) plus a one inch section from each of the sides folded to form the frame for the back. I plan to rivet on something with holes for air flowin the back. It needs no front or bottom. How can I form these bends on a small brake? If I bend the 1" pieces first, I can not grasp the piece back in the brake to form the top & side bends. (and vise versa). I'm thinking of milling slots at he bend lines for the 1" pieces to weaken the area so I can hand bend them last. But it seems like there should be an easier way.

Matt_Isserstedt
Posts: 275
Joined: Thu Jan 02, 2003 10:47 am
Location: Atlanta, GA

Re: Simple box forming question?

Post by Matt_Isserstedt » Wed Oct 15, 2003 3:23 pm

Here's a quick question.

Is your brake the simple kind which just puts 1 fold in the entire length or a box/pan/finger brake which has removable "fingers"?

If you have the finger brake, just remove a couple of fingers to allow the first two opposing sides to pass unobstructed thru the bender and then bend the remaining side.

If not, (and I assume this is the case by your post) then the game gets a little trickier. You really can only bend the two opposing sides. The third side will need to be bent by some other means.

I have used a hardwood block, cut to the length of the space between the first 2 bends, then clamped on the third perpendicular bend line to "guide" the bend and a large diameter mallet worked up and down the bend line several times to actually bend it up to 90 degrees slowly. I built a couple pans like this before I had a brake, and it will work.

The disadvantage is that since the metal isn't bent all at once as in a brake, the bend gets mildly wrinkled. Careful mallet technique can avoid this but the box/pan/finger brake is the best overall solution.

Notching the corners for the reinforcing tab can get somewhat interesting too. The geometry doesn't lend itself to a simple 90 degree notch, so then you are into tin-snips or special notcher tooling for your bender.

I hope this helped. If it's not clear I may have some pictures.

-Matt
The beauty of entropy is that it is self-maintaining...

Matt_Isserstedt
Posts: 275
Joined: Thu Jan 02, 2003 10:47 am
Location: Atlanta, GA

Re: Simple box forming question?

Post by Matt_Isserstedt » Wed Oct 15, 2003 3:24 pm

Oh yes, also, as far as the venting, my personal favorite is expanded metal. Only problem is... the internal cutting gets kind of interesting.
The beauty of entropy is that it is self-maintaining...

mcman56
Posts: 156
Joined: Thu Apr 17, 2003 2:30 pm
Location: Roseville, CA

Re: Simple box forming question?

Post by mcman56 » Wed Oct 15, 2003 6:33 pm

aaahhhhhh! Removable fingers! I'm using a machine at work and the top piece is made up of individual pieces. I'll check to see if those are removable fingers. If not you other suggestion sounds like it will work.

Thanks!

User avatar
Jacin
Posts: 1046
Joined: Sat Dec 21, 2002 12:14 am
Location: Near Cleveland, Ohio

Re: Simple box forming question?

Post by Jacin » Wed Oct 15, 2003 8:29 pm

I fully agree with what Matt has already said, but just to add a wee tiny bit......IF you DON'T have removeable fingers AND I understand your project then I would (in addition to what Matt has already suggested) consider 2 things:

1. Try to form the the 1" edges first then place the part such that it is on the very edge of the brake so as to allow the 1" flap to clear the dies - If I understand this correctly you have only 1 side with a flange so this MIGHT work.

2. If previous won't work - consider just "braking" each fold. In another words - lay out your part and clamp in your brake - fold (lift the leaf) just enough to give a CREASE in the metal.
Once creased you can go back and fully bend the 1" flange usign the brake in the standard way. With the CREASES already present you can now fold the three sides with just your hands and possibly a couple of 2x4's and some well placed hammer hits. You'll be surprised how well the bend will follow the initial crease though.

Now that I think about it - A handy tool to have are some furnace pliers - not sure if that is the right term - but they are basically a 4" wide set of pliers that you should NOT be without! They would be useful here to add the 1" flange LAST ESPECIALLY if you added the CREASES like we talked earlier.

PIECE OF CAKE ! ! ! ! ! <grin>

Let us know how you make out!!!!

mcman56
Posts: 156
Joined: Thu Apr 17, 2003 2:30 pm
Location: Roseville, CA

Re: Simple box forming question?

Post by mcman56 » Fri Oct 17, 2003 10:38 pm

Thanks for the help. The brake does have removable fingers and your reply prompted me how to use them. I was able to bend what I needed. Thanks!!!!!!!! Dan [img]/ubb/images/graemlins/wink.gif"%20alt="[/img]d

Post Reply