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Debugging the Homemade Box and Pan Brake.

The stiffening bar on the back f the hinged piece

The stiffening bar on the back f the hinged piece

In the last Post “Test 2 of The Box and Pan Brake – Making Progress” I said I was making progress. I am beginning to feel right now I am not although I think I am.  Most blogs and D.I.Y. articles do not post the mistakes and problems.  I have chosen to show the slow, painful details when things don’t go right because often they don’t.  That is especially the case when you are trying something new and learning.  In this case, I am attempting to show the process of learning and troubleshooting and that to me is more important than the final product.

I added the stiffening bar on the hinged piece of my home-made brake, but I am still not getting the tight, small radius, bends I had hoped for.   This is the kind of problems where I do a test, look at the results, walk around a day or two with the problem churning in my head, and then come back. modify and test again.  That makes it a very slow process.

The clamping edge set back by a 1/16".

The clamping edge set back by a 1/16″.

I added the stiffening bar, a piece of 1″ X 1″ X 1/8″ steel angle, to the back of the hinged piece and then bent a strip of 20 gauge steel.  This time when I set the clamping board, I set it back 1/16″ of an inch from the crack between the base board and the hinged board.  I later discovered that was too much. Once I had that board set, I clamped aboard behind it so I could easily loosen the clamps holding the clamping board to insert the metal to be bent.  In the long run I have other ideas on how to do all this more efficiently, but I have to get the fundamentals down first before proceeding on to that.  To do otherwise, I will be throwing more time, money, and effort at something that just won’t work. Even worse, if I add the extra “stuff” and then go back and modify, I will have even more to modify. So for now progress looks slow. Mostly because it is slow.

The first two bends on this series of tests.

The first two bends on this series of tests.

I did the first and second bend on this piece of metal. I am not happy with the bending radius and I don’t really see an improvement over the previous tests.  My first question was:  “Maybe my expectations are too high?” Since I have no experience with bending metal on professional equipment it was time to determine what I should expect and try to figure out a way to measure it. To this point my measurement as been judgement through an uneducated set of eyes. Time to educate myself. I went to the web and searched for metal bending radius and found a site with a nice table. For 20 gauge steel, the minimum inside bending radius I should be able to obtain is 0.031″. Now how do I measure that?

My inside radius scale

My inside radius scale

After some walking around and thinking I decided the best, cheapest way I could think of to measure the inside radius was to use CAD and draw a series of circles of various diameters and print this full size. I can then look inside the bend and compare it with the circles. I got all that done and my radius is over 0.100″. My eye was correct the radius is too large and now I have a method to measure how much too large.

I again set it up to bend a second piece of metal, but this time I set the holding board flush with the edge of the base board.   1/16″ is 0.0625 which is greater than the desired radius but obviously if I set it at 0 and things were operating correctly there would be no clearance for the metal.   Things are not operating correctly so it is time to figure it out.  This is the old “make it or break it” test.

The next two bends with the zero offset of the clamping board.

The next two bends with the zero offset of the clamping board.

When I did the next two bends, again there was no improvement on the bending radius.  More head scratching.


Looking down at the gap between the hinged board and the base board.

Looking down at the gap between the hinged board and the base board.

When I raised the hinge board up to ninety degrees I looked and saw a significant gap between the hinge board and the base board.  This is what the stiffening piece of metal was supposed to prevent!  What happened?  I then looked and noticed the gap is the same all the way across the board.   I then remembered what I discovered way  back there when I first assembled the hinged board to the base board I noticed the hinge board had a bow in it. (Progress on the Sheet Metal Box and Pan Brake.)

The next few steps are:

  1. Remove the hinged board and sand until I remove the bow.
  2. Remove at least 1/2 of the looseness in the hinge between the hinge pin and the leafs.
  3. Reinstall the hinged board against the baseboard.  This is going to be a little bit of a problem because I will have to fill the existing holes for the screws install new ones about 1/2 of the hole diameter to the rear. of the exiting holes.

If that does not improve things a 2nd test I will do is bend metal only about 1/2″ wide.   This will put much less stress on the system and should produce a tighter bending radius.

Meanwhile I will start producing some blog posts on other subjects just to keep something interesting up here while I scratch my head on this thing.


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