Welding Fab and sheet metal table Project.

[Wanna-Be]

I am building a welding table with DIY a sheet metal brake brake on one side. The table top is 3/8 steel with 1 1/2"X 1 1/2"X 3/8" angle around the sides, flange leg out to double the table thickness. On the sheet metal brake side I will form a square tube section under the table edge with a second angle, of the same size and fully welded this and the table top and machine finish.
Notching, of course, for the the leaf hinge pins at the ends. The leaf design is still under developement in my head.

The hold down would be fairly simple if I wanted to settle on just flat work but I want to do some box work so that complicates things some.
Here are my thoughts; I will set my hold down bridge/board back a few inches, making it of heavy angle, channel or heavy Tee would be much perferred. Hinge on the back side, offset for metal clearance and provisions for fitting individual fingers.
Now to the clamping pressure for the fingers, I have some very heavy sturctural fabrication C-clamps. Nothing cheap, forged with 3/4" screws with square heads and blunt clamp screw ends. Must weight 40#! The clamp foot is about 1" X 1 1/4" sq. and I could cut a hole in the table but that would be into my perimeter angle re-enforcment. I don't like that. The clamp throat isn't deep enough to reach over the table edge.
I'm thinking cut the clamps back frame and weld them to the table. That would get me 3" closer to the hold down fingers. The location would be off to the side, just between leaf hinge and the hold down brdge/board hinge, giving clearance for the sheet metal in the brake.

Now, I would assume that welding the modified forged steel clamp frames would be the same as ordinary steel, however, what would this do to the strength properties. I have welded a lot of heavy fabrication over the years but don't remember if there is anything special about forged steel. That was always with rod and some weld procedure told me what to use. Now I use Mig and would be hard pressed to even find my stinger even if I had the right rod. I have done stainless mig as well and have done a lot of mixed gas welding of that metal.

This last point/questions are why I brought the "Project Ramble" into this forum (thanks Harold and Scott).

Steve

[Wanna-Be]

Just to respond to my own post (I do that alot, could call it a "second thought")!

After thinking this through again, I would take the clamps "off the table" so to speak. And build an over arm on each end of the bridge frame then using the method of a standard manual brake. Use a lever with a link that drives downward onto the bridge frame and latches after the lever drive pin is over center of the lever axis pin. Similarly the lever, when released could lift the bridge frame and fingers off the work piece.

The rear mounted hinge would provide alignment and adjustment of the frame and finger leading edge. (thinking out loud again)

I'll follow up with some progress reports and pictures and this project developes.

Thanks,

Steve

[whateg0]

I think you'll like the toggle mechanism better than the screws, especially if you end up making repetitive bends. I built a brake a long time ago using a set of T-bolts and it works fine, but it's a PITA to unscrew the clamping bar after every bend.

I'd like to comment on the vertical strength of your setup, as well. I don't know how tall the tubing under the table is going to be, but I would advise you to go as tall as reasonably possible. It is pretty surprising how much force is pushing down on the table and up on the clamping bar in the middle of the bend. And it's surprising how much the table will deflect. I don't know how wide your table is, or how think you intend to bend, but when the parts all bow outward, the result is a wider radius in the middle of the bend. If you look at commercial brakes, they all have a truss built under the table, above the clamping bar, and into the bending leaf for this reason. On my 2.5' brake, I used 1-1/2" x 3" x 1/8" steel tube under a 2" x 2" x 3/16" (IIRC) angle for the bending leaf and when bending 2' wide 16 ga, I can see it deflecting in the middle.

Dave

[Wanna-Be]

Thanks Dave,

This is a work in process (inside my head) right now. The only thing I have at hand now is the table top from a scrap yard ($26) 32"X40"X3/8". I was hoping to find something 1/2" or even 3/4" but was glad to get this since is has mill end on two sides and sheared on 3rd and trouch on the 4th. I will use the sheared side for my brake edge with. Since I couldn't find a good deal on square tubing I am going to use some 3/8" angle all around, under the tabe with the flange leg towards the perimeter for work clamping on three sides. The brake side will have a second 3/8" angle inverted and 100% welded to from a box section. This will be further reenforced with a the truss and tensioning screw you mentioned. Same on the leaf and the clamp bar.

The existing table width, being the limiting factor, I expect I will end up with 38-39" and the gage will depend on the width of the sheet I will be bending. I have seen the results when exceeding the rated limits in the cheaper import brakes and will have to determine mine as I "sneak up on the limits". I hope to do 16 gauge at least.

BTW. The method I have in mind to adjust the finger nose-to-leaf clearance for different gauges will be a adjusting screw in the back hinge pocket (no hinge pin, just capture the radiused end of the hinge). Trust me, it makes sense in my head!

I think I have the "toggle" system worked out and will have to get that out of my head and on to a drawing since there will be some machining involved (Yah!) Oh BTW, I Plan to finish the table top and brake fabrication before installing the table legs so I can get it up on my K&T horizontal mill to fininsh some of the brake edges and surfaces. Also might do some of the component drilling and boring as well. (I wish my horzontal boring mill was operational since this would be a perfect project for that, OH well! someday it will run again!

And all of this because I need to make 4 sheet metal boxes. What we won't do to avoid going to "another man's shop".. Really it is because I always wanted my own brake, I got a Jet 16 gauge Jump shear at auction so that problem is solved for now.

Steve

[whateg0]

...
And all of this because I need to make 4 sheet metal boxes. What we won't do to avoid going to "another man's shop".. Really it is because I always wanted my own brake, I got a Jet 16 gauge Jump shear at auction so that problem is solved for now.

Steve

We've all been there before!

I would be careful about any welding you do to the table top. While it was lighter, my 3/16" table warped like crazy when i welded the angle frame to the bottom of it. And that was 1" welds about every 6". If you are welding the angle to form a tube, I'd do it before attaching it to the table top, just in case it decides to bow, though in theory, if it pulls at all, it should pull back when the other side is welded.

Dave