Bending square u-bolts with shop press

[jmc]

FYI, 8mm is .316" and 5/16" is .312", 10mm is .394" and 3/8" is .375", rounded to 3 decimal places. So both 8mm and 10mm are thicker than the nearest fractional equivalent. If you are finding the opposite then I would change where I was buying the stuff. I was surprised that the 304 bolts you ran the die down threaded easily. But then I considered the fact that they were from China. Before I retired a couple years ago I had several customers who would not accept and metals from Asia. I had to provide certs showing country of origin. I didn't blame them either. I had stopped buying and metals that came from China or India. Too often the metals did not meet spec.
Eric

I think I've seen bolt shanks smaller than their thread OD and I think it's because they use a rolled thread. The rolling process displaces some of the metal, which enlarges the threaded portion's OD, so they have to start with smaller stock to compensate. That doesn't account for SAE stock being bigger than their metric equivalent unless the SAE manufacturer chased their threads.

 

[etpm]

I think I've seen bolt shanks smaller than their thread OD and I think it's because they use a rolled thread. The rolling process displaces some of the metal, which enlarges the threaded portion's OD, so they have to start with smaller stock to compensate. That doesn't account for SAE stock being bigger than their metric equivalent unless the SAE manufacturer chased their threads.

That's correct, rolled thread and smaller shank. Virtually all fasteners made today have rolled threads. Not only are they easier to make they also generate less waste and have stronger threads. Some fasteners are made with no machining at all. Wire is cut into lengths with a shearing cutter, then the fastener is put into a stamping machine to form the head, then the threads are rolled.
Eric

 

[grsthegreat]

I have seen chinese ss rust more often than not. And will stick to magnet. Not a good sign.

 

[jmc]

I have seen chinese ss rust more often than not. And will stick to magnet. Not a good sign.

Checking stainless with a magnet can be misleading. 300 series stainless can be either way, depending on how much the mill cold worked it. Most 400 series (often called cutlery alloys) are magnetic, and also the common precipitation hardening alloys.

 

[etpm]

I have seen chinese ss rust more often than not. And will stick to magnet. Not a good sign.

300 series should not rust or be more than very slightly magnetic. When 300 series SS alloys are cold worked they can become magnetic so where a part has been bent or upset, like a stamped out part. But if, for example, sheet goods are magnetic away from any bends that is a pretty good indication of inferior quality "stainless steel". SS will rust if it is a magnetic SS alloy, such as 400 series SS alloys, or the precipitation hardening alloys, like 17-4. Another way SS will rust is if it has non SS steel particles embedded in the surface. This can happen from sloppy processing, like when a mill rolls out a bunch of mild steel sheet and then SS sheet is rolled using the same rolls. Or when SS sheet is rolled in a factory where there is mild steel dust in the air and this dust is rolled into the surface of the SS sheet. The particles are too small to see but will eventually cause rust and the only way to stop this rust is to use chemicals, like some acids, to dissolve the free iron particles, or to use mechanical methods, like polishing the surface, to remove any free iron particles. You are right, I too have seen a lot of SS that has come out of Asia that is magnetic and rusts. Garbage stuff.
Eric

 

[p122654]

I am refurbishing an old Cox boat trailer and have been searching and searching for the correct size square u-bolts to fit various applications. I have decided it's impossible to find something you can live with, never mind finding a size you want.

Has anyone fabricated a "die" set up for their shop press that does a decent job of bending square u-bolts?

Seems like it should be pretty straightforward ...

Thanks,
Tim

 

[ROUSTABOUT]

The biggest problem with bending your own is cracking at the bend. Depending on the stainless alloy used and the source of the stainless and the radius of the bend you may find visible cracking. You may also see what doesn't appear to be cracking but instead just a slight change in the appearance of the surface finish of the metal after bending. And change in the appearance means the metal is cracking. If the surface just looks duller then sanding with maybe 400 grit sandpaper and then polishing with 600 or higher grit or even better polishing with tripoli buffing compound must be done to help prevent cracking down the road. Visible cracking must be removed completely. Heat can be used on SS to make bending easier and to help prevent cracking but any heat discoloration must be removed to prevent rusting, which will for sure happen. Oh, and I almost forgot, threading SS with a die is a real chore and I would avoid that if I could. Your best bet is to do as others have suggested, drill holes in a plate. The preceding advice that I just gave is from experience gained from my 40 plus years working as a metalworker and machinist and from seeing bent stuff fail from bending induced cracking more than once.
Eric

I put a 1 ton rear and a lot of springs in my truck. I already knew about cracking and bending. I used four pieces of grade 10 all thread, gold, 5/8", on each side. Never had a problem after humpteen jillion miles. Had me self a one ton 4x4 after that, dually.

 

[animal12]

Like mentioned any automotive spring shop can make them . I've been around boat trailers for @ 60 yers & I've never seen any need for stainless u-bolts . If you have all thread u-bolts you better have good insurnce . From another forum " If it's soft enough to bend without cracking, it's too weak to take the axle loads "
YMMV
animal

 

[EABill]

I am refurbishing an old Cox boat trailer and have been searching and searching for the correct size square u-bolts to fit various applications. I have decided it's impossible to find something you can live with, never mind finding a size you want.

Has anyone fabricated a "die" set up for their shop press that does a decent job of bending square u-bolts?

Seems like it should be pretty straightforward ...

Thanks,
Tim

Try a NAPA store. they have them.

 

[not2old]

You'd be better off drilling flat steel stock and using bolts and nuts than trying to bend your own. As MB hints, bending All-Tread never ends well.

I agree, and you could use galvanized carriage bolts if you are able to make square holes. Grade 5 hex bolts might be a safer option as grade 5 carriage bolts are hard to find.