Standard radius for metal forms

Hey TT,

Varies by producer, and not only that, on "most" standard angle, the "legs" are tapered and not of constant thickness, so it won't form a

90 degree "inside" corner.

Take care.

Brian Lawson, Bothwell, Ontario.

I've drawn the shapes in my scrap pile into my CAD library, and found that different lots of the same nominal size varied in the details such as inside radius and the parallelism of channel flanges. The surface finish of angle was poor enough that even the correct radius didn't fit tightly without some cleanup with an angle grinder. The flanges of some of the angle are slightly tapered and only the outside is square. I think what you get depends on the amount of wear on the rolls that made it.

Can you specify angle bent to a known radius from flat strips?

Square tube has some fairly loose specs, hot rolled product is even looser.

ASTM specs for tube call for the corner radius to be no more than 3x the wall thickness. This means that a 2" square tube with .250 wall could have 3/4" radius on each corner with only 1/2" of flat. This would look more like a mildly deformed piece of round pipe than a traditional square tube. What this means is that the mfg can make most any reasonable radius on the corners and it will meet spec. It also means that you can not depend on the radius to be the same from lot to lot.

When they mfg square tube they take some slit flat stock, roll it up, weld it, then run it through a 'turk's head' roller to make it square. If the slit stock is a bit narrow, the round portion will have a smaller diameter, the resulting square section will have more rounded corners. Since the mfg buys his steel by the pound, they have incentive to use less, results in rounded corners on the cheaper tube.

Hot rolled angle is even worse. The only dimension that you can reasonably count on is the 90 degree corner, and even that varies some. The leg length can vary considerably, a 3-3/4" leg length on 4" angle is fairly common. The inside shape is done with a roll that will vary from one rolling mill to the next, multiple rolling dies at the same mill may be more or less worn so you can't even count on the shape being the same. Some will have a very large radius in the corner, some will have tapered sides, some will have a smooth rounded edge, others will be almost knife sharp. Most of this product is made is US mini mills from scrap or imported. Neither is what I would call a 'prime' producer.

The horror story: we set up a robot to weld a frame that included some

4" angle brackets. The position was fixed by a stop block on the 90 degree face, the robot welded the lip. Things started out ok, then we had a series of weld failures on the angle bracket. It seems that the robot expected 4" legs, the low side tolerance was around 3-3/4". The robot was welding a bead on the base metal, never even got near the angle. We had to put in a "sense" op in the program where the robot head moves in to find the edge, then starts welding. Slowed it down tremendously, gave up on that. Finally had the robot weld the back side to position the part, did a final edge weld manually.

It's amaz> Can anyone point me to a table with the standard radius for corners for

Yep. And even the outsides aren't 90 deg. At least on the aluminium I've used, some 3 x 3 x 1/4. ...lew...

thito01 had written this in response to

: It sounds like I am in need of a solution instead.

The application is simple. A small equipment trailer made out of iron 2x4 tubing. I wanted to mount the axle springs on a sub-assembly made from angle iron that will then be bolted to the 2x4 tubing. If my needs change in the future, I can then move the sub-assembly forward or backward to adjust the tongue weight for the new piece of equipment. So, I needed the inside of the angle iron to be true instead of the outsides. Is there such a thing? Or, should I just take some of the 2x4 tubing and cut it diagonally to create two "L" profiles? Or weld two flats together to make the angle?

I wanted to bolt though the sides of the angle iron and though the tubing. Maybe just using some flat and bolting vertically on each side (front and back) of the spring hangers would be an easier solution.

Maybe, just forget it and weld the spring hangers and just cut them off and replace them if I need to change the function.

TT

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You don;t want "angle iron" you want "steel shapes", "L shapes" in your case. Google on "steel shapes" to get an idea of what is available.

Cheers,

Bruce (bruceinbangkokatgmaildotcom)

Why not fabricate two or three sets of hangers and weld one set on now. Mount the springs with anti-sieze on the bolts and cottered castle nuts. To move them, flip the trailer over, weld on another set and move the springs. I think squaring and aligning the axle assembly to the tongue would be hard to do with the complete, installed axle but simple for four hanger lugs strung onto a long threaded rod..