Deformation when splitting tube

[quarencia]

I'm considering cutting a 3x8x1/4 steel (A500) tube down its length to create two open "U" channels 3x4x1/4. Does anyone know if the two halves will stay true or will they deform from internal stress in the tubing when split? I've never split tubing this way.

Or conversely, does anyone know where to get 3x4x1/4 "U" channel. Not a profile I've ever seen before.

If it matters, I'm building pin-on mounts for a grapple to go on my Kubota loader. The adapters in the attached drawing will be welded to the back of the grapple.

Sorry if this doesn't belong in welding, but the project will involve welding.

Thanks,

 

[mrmikey]

You'd probably be better off getting a couple pieces of 3 x 4 x 1/4 rectangular tubing and cutting that down, it'd be cheaper and more than likely more readily available than 3 x 8 if they even make HSS that size.
No matter which way you go, it's going to deform a bit but nothing that you shouldn't be able to straighten out with a bfh and a few love taps or a bit of well placed heat. If you can, try to cut off the side with the seam, that's where the majority of the stress will be.

 

[quarencia]

You'd probably be better off getting a couple pieces of 3 x 4 x 1/4 rectangular tubing and cutting that down, it'd be cheaper and more than likely more readily available than 3 x 8 if they even make HSS that size.
No matter which way you go, it's going to deform a bit but nothing that you shouldn't be able to straighten out with a bfh and a few love taps or a bit of well placed heat. If you can, try to cut off the side with the seam, that's where the majority of the stress will be.

I thought the same thing about price. Then I priced it and the 3 x 8 was cheaper! The difference is, I can get two 17" pieces from24" length of 3 x 8, but I'd need 36" of 3 x 4 to get two 17" pieces. Have a press and various bfh's for straightening as needed. And taking the top off two 3 x 4 lengths to get the u channel is about the same amount of cutting to split the 3 x 8.

I verified the seem on the 3 x 8 is centered on the 8" side and I'd be cutting that off.

But I've probably overthought this already.

 

[Rustyiron]

If you plan it out before splitting, you could drill through both sides, say 1/2" hole and weld in a rod at 2 locations (looking at your drawing) with one of them being between the mounts. If anything they'll want to spread after cutting.
If you really want to do it the right way, you could use the right size (good luck) heavy wall DOM pipe the right size for your pins and weld in all 4 before you cut it down.
I'd want more like a 1/2" on each side (around the pins) of that new channel for strength and wear at the pins if you stay with your design.

 

[Rustyiron]

Wouldn't a pair of 3" x 1/2" angles (for each side) mean only drilling for the pins?

 

[chim]

I split a 2x2 with 1/4 wall with a saw and it spread a fair amount.

 

[threepiece]

Structural square or rectangular tubing will begin to separate as the lengthwise cut progresses. If you have a press you can straighten it.

The trick is to block the piece up a small amount at a time so there is no chance of over bending. Add small increases of blocking as needed.

 

[BlueKnife]

Probably be less hassle to use a couple pieces of flat bar for each side.

 

[Tractor Seabee]

Ask your steel supplier about "Ship Channel", "Deep Channel" or "Wide Flange Channel". All terms I have heard used but never used myself. I will ask at my supplier next visit. May find something their you can use/adapt to your project. Making it from flat barbe sure to step weld to reduce distortion. MIG produces less heat distortion than any other process, still step weld in short 1" increments.

Cutting steel tube: Don't try to get two pieces out of one, use a cut off wheel on a 4 1/2 grinder and cut off one side of a selected tube instead of down the middle. Welding up flat bar has its own set of problems.

Ron

 

[CalG]

structural steel tubing production involves roll forming, bending, welding, and then straightening.

The material is under so much stress that any "cut" will send the base shape into a tizzy.

I'm sure some esoteric heat treatment could reduce the distortion, but there will be some.

Buy the stuff you need, It's not that costly!