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Mcgyver
12-27-2006, 07:37 PM
hope everyone had a great Christmas!

I'm looking at various sheet metal brakes, particularly the brake by J. R. Williams - Its a simple and solid design imo, got the plans on the web somewhere.

Has anyone built or used this design?

given my lack of experience with brakes, two things puzzle me. First, the back of the clamp plate is about .600 above the bottom plate....when in the clamped position, the clamp plate is like 5 degrees acute to the bottom. Makes sense that you want to ensure the work is clamped at the bend, but this seem a lot, I'm wondering it there is some other function or reason that the back of the clamp plate should be this high above the bottom plate.

Secondly, the eccentric generates about 5/8 of space between the clamp and bottom plate when open - obviously in excess of what the sheet metal needs! Why have the opening this large - if the eccentric movement was less, there'd be more clamping pressure. Is this opening to facility used to finish the fold over on edges or some other use?

thanks

CCWKen
12-27-2006, 08:36 PM
First, the back of the clamp plate is about .600 above the bottom plate....when in the clamped position, the clamp plate is like 5 degrees acute to the bottom. Makes sense that you want to ensure the work is clamped at the bend, but this seem a lot, I'm wondering it there is some other function or reason that the back of the clamp plate should be this high above the bottom plate.

It adds considerable strength while keeping the clamp plate thin and allowing for greater than 90* bends. If the plate were flat, some reinforcement would be necessary above it to reduce flexing. The reinforcement would be in the way if you wanted to make back-to-back bend for say, a channel.


Secondly, the eccentric generates about 5/8 of space between the clamp and bottom plate when open - obviously in excess of what the sheet metal needs! Why have the opening this large - if the eccentric movement was less, there'd be more clamping pressure. Is this opening to facility used to finish the fold over on edges or some other use?

Yes. It allows you to make compound bends and gives clearance for removing a piece that may have two long legs--Like a box wall or large double flange. 5/8" isn't much but it helps.

J. R. Williams
12-27-2006, 09:04 PM
Mac
The brake started out with an idea and grew from scrap materials I had on hand. The space does provide plenty of room under the top bar and the open height helps with short flanges. I would revise the next version to include adjustable fingers but have found this one quite satisfactory. The cam action provides plenty of force to close small flanges. The original article was published in The Home Metal Shop Club news letter and later a gracious member borrowed the unit, made a set of CAD plans that are available from the Club's web site. The set of plans follow my design very well. The hinge bolts are hardened steel shoulder bolts with needle bearings.

J.R. (Joe) Williams

Mcgyver
12-27-2006, 11:27 PM
guys, thanks so much for the education and it's great to hear from the the creator! I've spent a lot time at the Home Metal Shop Club, great site. I'd saved it as a future project and couldn't remember where from, credit to R Kostelnikek as well for the drawings. here's the link, last entry on this page
http://www.homemetalshopclub.org/projects/project.html

it seemed like a design that would easily allow for the clamp to be swapped out for a finger/box and pan style clamp at some point, but I don't think I'll bother initially. The big change for me is to use 4x1.5" channel for the bottom and clamp; it's lying around and should be a strong profile. It will require a welded fab vs bolted. That'll make some things easier & creates a few new troubles. was going to do lots of short welds staggered around it to minimize twisting. Joe, did you ever consider welding?

the bending platen bearings are needle bearings? any other words of advice would be appreciated!

DeereGuy
12-27-2006, 11:45 PM
I have had that downloaded for a year or so now. I printed it off and haven't gotten around to starting it yet. I am in the process of finishing up a gear driven slip roller that I got plans off the net for. I want to start this bender in mid January I hope. Thanks for the great plans.

J. R. Williams
12-28-2006, 12:04 AM
mac
The bearings for the platten are needle bearings running on socket head shoulder bolts. The bearings came from an old airplane that I helped a friend cut up for scrap. I would shy away from welding as warping will be a problem. The material was all from a welding shop's scrap bin and I had band sawed the parts to rough size and used the mill to square up the parts. Bolting allows some freedom in assembly **** K added a couple eye bolts so a length of bar stock could be used for lifting. The unit is heavy and hard to handle.

Joe W.