Just what does the profile look like for dies used to bend square tube? I would like to either adapt some home made dies to the HF pipe bender or the hosefield (sp) type of bender that HF sells if its possible. I know I had a set of dies one time for bending up square tube but darned if I can find them now or remember what they looked like.
I have bend some pretty decent radius in square tube with a set of home made dies made out of a pieceof steel pipe and the homebrew press brake, but I prefer to have a more smooth radius on the tube. Would like to go 180 if possible, and the tube size / gage would be 1/, 3/4 and 1" in no more than 14 ga more than likely mostly 16 ga.
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I created one using scrap I bought where I buy my metal. They have round "cutouts" from different thicknesses of plate. They have a small notch and hole at one point arond the edge where the torch was started but otherwise they're clean.
I picked up one that was 3/4" thick by maybe 8" diameter. I also found a couple that were 1/4" thick with a diameter about 1.5 or 2" larger than the
3/4" piece. I sandwiched them together, drilled a 5/8" hole through the middle and and a couple of holes to put bolts through to hold the whole thing together and that's my die for 3/4" square tubing.
Works great on the HF hossfeld style bender. The only problem I've had is that the bolts that hold the 3 plates together get in the way if I want to go over 90 degrees but I could fix that by countersinking the holes in the top plate, threading the ones in the bottom and cutting screws to the correct length.
I also tried it for 1" with another center piece but the tubing I had was very thinwall and it didn't work so well.
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Square tube dies are typical 3 pieces: a core with the correct diameter to match the inside radius, and 2 side plates to contain the tube. Bolt them together and you are done.
The devil is in the details: the core needs to be about .005" thicker than the tube, you can get there with shims or just clamp it down tight. But if you don't give it some clearance, you get some pretty hefty scuff marks on the sides. The side plates usually need to be loosened to get the tube off. Use some grade 8 bolts or else you will have galled bolts by about the 5th bend.
Bends over 90 degrees (or less) are problematic on a hydraulic bender. The additional stroke causes the end supports to need a LOT of logitudinal travel under very high pressure. If they don't roll or slide easily, you will crumple the tube in the bend area.
You have your choice of trying for a smooth inside or doing a controlled 'crush' bend. Take a look at a lot of the cheap stacking chairs, the inside of the bend has a heavy crease. This allows the metal to flow somewhere, minimizes the cosmetic ripples. You can do this by putting a rod around the center of the bend die, start with a rod about 1/4 the size of the tube.
Bend RADIUS should be at least 4 to 6 times the tube size if you are trying for a smooth inside of the bend. Crush bends can go down to about 2 to 3 times and still look nice.
I have personally found that I can't do much better than a 45 degree bend on 1" x.083 wall square tube on my pipe bender before I start crumpling the tube.
The commercial draw bender folks can do a tight radius with uniform cross secti> Just what does the profile look like for dies used to bend square