Will Seamless tubing spring when sawed in half lengthwise ?

The tube size is 6.5" ID .250" wall 20" long. The job is take a clean up cut off the OD and ID so they run true with each other and split it down the center lengthwise. This is easier said than done on a tube this size. The halves do not need to mate back together to form a round tube. They are getting clamped back together over two 6.5" Dia rollers to straddle the distance between them. This is just a setup tool. Its not going to spin or move in anyway. They will take a measurement and remove them. My first thought was use a piece of honed tubing. The ID is already done. Take a clean up cut off the OD and saw it in half. I told them it was going to spring. The only way I could see keeping it straight is to take 2 tubes and saw them just over half. Mill the split line. Clamp them back together somehow to turn and bore it. The length makes doing it this way a challenge though. Also it would be very expensive to do it this way vs sawing it in half and its done. I didn't know if seamless tubing would spring like welded tubing does.


Thanks
Aaron

Stress relieve (heat treat) first - thoroughly !!! and IMHO you stand a good chance - all other bets are off.

The piece of rather smaller seamless steel tube I tried to cut lengthwise certainly moved due to locked in stresses and needed persuading back into shape. Fortunately not a precision job so it worked out. Keeping things sufficiently accurate for an alignment jig would, I think, be another story.

Maybe hydraulic tube would behave better if it can be found in that size for a reasonable price.

If extruded aluminium tube will suffice then I have split such with no visible movement.

Clive

Buy a 2 footer (I'm assuming just one part), take a small slice off of each end, machine em, then
split em and see what happens. If they don't move, then I would say you are good to go.. If
they do *sproing!!* then make sure you have enough time to send the tube out for stress relief.

If its just A36/mild steel tubing or pipe, I think you might be ok. Alloy steel or a heat treat
involved then things can get ugly..

A.Delaney said:

I didn't know if seamless tubing would spring like welded tubing does.


Thanks
Aaron

Click to expand...

My experience is yes it does but not nearly as much as welded seam tubing.

I'd take a stab at it by buying a longer piece and cutting it to length, experiment with the drop, to see how much it opens up when sawed in half. If it opens .020, then bore the good piece .025 under and saw it apart. The .005 will make it a good tight spring fit when the 2 pieces are clamped in place. Rude and crude but the job sounds like it's warranted.

IME it won't just spring in dia but it will also sorta banana, you won't just end up with a straight gutter section of the wrong dia it will also be bowed longitudnally and if it goes like every other piece i have cut with the curve side down will put the ends up.. Never done it with tube this large only smaller though.

Sami's anneal is the best advice, but im still not sure you will get prescion, theres a reason stuffs not made this way - done like this.

That stuff is gonna bend.

Triple anneal and try.

It's really a "suck it and see" situation.

This is 2.375 od x .188 wall DOM. I cut it in thirds for rebuilding pneumatic expanding arbors. Never saw any warp on these.
1_189_zpshrvtk4.jpg Photo by rbehner | Photobucket

I've had bronze tube stock go the other way and pinch the blade.
Had to leave stock and clamp together and turn and bore to true up.
No oven big enough so never considered stress relieving.
Any steel tube I've ripped in half has warped along the length and across the diameter.

Dave

In my experience, almost ALL steel tube will move when cut like this. I have spent plenty of time stuffing wedges in saw kerfs to keep the blade from getting pinched while sawing in such a manner. Stress relief will help but may not entirely eliminate the problem. If you NEED the part to stay straight and true for precision measurement you probably are going to need to saw the tube then mill the split line then soft solder the halves together, finishing ID, OD and faces afterward. I've done many MANY sets of split bearings in large presses this way and it doesn't take that long really. After machining just give the bushing a stout tap with a dead blow hammer and it will split right in half.

P.S. with that wall thickness and diameter:length ratio you may even have a tough time getting the part to stay straight for the duration of a single OD or ID cut.

Getting honed tube is a good idea. Turning the o.d. and not getting chatter is going to be the biggest challenge. You'll probably have to do it in 2 cuts, one to measure for taper and a 2nd to offset for it. From the sound of it, i wouldn't think the flex after cutting will be a problem, considering the way its going to be used.

If this is just a setup part, can you use something centifugally cast? Probably would be more stable

Well I cut a piece of the tubing and it sprung an 1/8". Not only did it spring but it scissored as I was sawing through it. This was just not a good idea. I think sawing two halves. Milling the split line and finish machining is really the best way to make this right. Or use seamless 1" wall tubing, but it will weigh a lot.