DIY Telescoping Round Tube

I want to make some telescoping stands and am planning on using SS 1.25” Sch 40 pipe and SS 1” Sch 40 pipe. I have cut the 1.25” pipe to 4” lengths then cut them vertically with a .125” cut-off wheel and need to weld the pipe back together (see pictures). This will give me the tight tolerance I am looking for. The first 1.25” pipe I cut has a gap between .125” - .188”, and the second is .125”. I have read that people use copper as a backing for SS so my plan is to put some solid #4 copper wire on the inside of the 1.25” along the cut and weld the pipe back together. I need the inside of the 1.25” pipe to be smooth so the 1” pipe slides freely.

My questions are:
Does the copper and SS filler not weld together?
Does this sound like it will work?
If not any suggestions?

Attachment 5270Attachment 5271Attachment 5272

Thanks

#1 - No, the SS and the copper will not weld together.

#2 - 4 gauge wire is only .2" diameter. Seems a little flimsy to me. Could you even straighten it well enough? (since the wire came spooled, it is probably not even straight to begin with?)

#3 - You might consider getting a 6" or so long piece of 1/2 or 3/4" copper plumbing tubing, and clamp that at either ends using small c-clamps. It should be rigid enough to easily clamp at both ends with small c-clamps. Maybe you could even just clamp the copper pipe in the jaws of the vice with the end hanging off to the side, and hang the stainless steel pipe on top of that to weld to it. I don't think you could do either of those with 4 gauge wire. There are thicker solid copper round stock available from places like onlinemetals but I was thinking copper plumbing tubing might be more readily available for you.

Alternately, you could use a thick aluminum pipe/tube or solid round as a backer for stainless steel. Try to keep the direct arc off of the backer.

No, the SS filler will not stick to the copper. You can use aluminum too. In fact, to get the effect you're looking for I would suggest a bigger aluminum bar (at least 1/2"). There won't be enough heat available to melt either.

If you're new at welding stainless, there's a couple things to know. The unprotected side of your weld will grow big black oxide crystals if left unchecked (ie, back purged). A close fitting chill bar (what you're talking about) will limit this as it limits the amount of oxygen available to the weld. If you want to eliminate the black crud entirely, you can back purge with argon. There's also Solar Flux which I guess you can stuff between your chill bar (copper) and the weld to take up the headspace but I haven't tried it myself. If you don't care what it looks like inside, but just want to prevent the weld from ending up intruding into the ID, your bar will work fine.

The second thing is that stainless warps, due to the two-punch high coeff of thermal expansion and (for a metal..) insulating properties. The shape is good for that but I'm worried they may end up a little bent. Take your time and go with short welds if you want to prevent warping. (Good contact between your chill bar and the stainless helps, but I don't think you can really have that with a piece of round.

Since you've got the SB, I suspect you've got some larger hunks of aluminum round around. :)

EDIT: jakeru you beat me to it!

What is your "Telescoping Round Tube" for? A TV antenna?

Agreed to what paul said. Though its only 4 inches. If it were a longer run you would definitely get a bend going in the pipe. When youre done welding you can passivate the stainless with pure citric acid.

Am I missing something here, cause if you want a tight slip fit won't be achieved by cutting and rewelding a seam, how do you plan on keeping it round, you have a lathe why don't you substitute the sliding piece with solid rod say..3/4 inch and build some bushes on it to give you a nice slip fit,,,this doesn't seem like a welding fix to me,,,more like a machine job.

Not to be immodest, but I did a set of telescoping legs as a project. It is a different approach, but worked out well for me. Might not be worth the trouble for just 1 or 2 though, and it does require access to a press.

http://www.everlastgenerators.com/fo...lescoping-Legs

Jakeru/Paul-
Thanks for the tips. I did get the copper wire to be straight (guy at the hardware store was a little irritated) 5” anyway and it lays right inside of the tubing. I looked at copper tubing and it was a lot more money than the wire, but if the tubing would be better then I will spend the extra money. I did not realize that I can also use aluminum, which I might use since I think I have some ½” aluminum round bar. I am planning on tack welding the ends and center then welding the rest about a half inch at a time to minimize/eliminate warping.

JP-
I am making stands for my pig roaster.

Dyethor-
What do you mean passivate the stainless?

Geezer-
I used my vise to get the tubing back to round, and I only removed about .125”. I was surprised how well it worked. What do you mean by bushes?

Redbeard-
I like your idea but I am going to use pull-pins (detent) to raise/lower the spit up and down equally.

Passivization or pickling stainless is a chemical process that eats off all the iron and iron oxides on the surface of the stainless. So the top layer is all chromium. I have found citric acid is the safest chemical to do this. Also there is stuff called pickling gel/paste, you put it on your welds and HAZ, it will clean the scale and get rid of the discoloration. Its all to help inhibit corrosion. Nothing looks worse then rust on stainless.

Geezer-
I used my vise to get the tubing back to round, and I only removed about .125”. I was surprised how well it worked. What do you mean by bushes?

I should have said bushings, whenever I needed a precise slip fit of one tube into another, the inside dia of the outer tube can be much larger than the outside dia of the inner tube, I take a bronze bushing machine it down to fit in the outer tube and the bushing is usually a good fit for the inner most tube outside dia. without machining (standard inner bush sizes)

A press fit of the bushing into the outside tube or some JB weld will secure it in place with proper alignment.

What it means is you can use a much larger outer tube with a much smaller tube inside and still get a nice tight slip fit.

Did you say JB weld??? :O

Citric acid is a good tip!

My pickle juice is a mellow blend of nitric and sulphuric acid, with a dash of hydroflouric acid in a convenient paste format with an indicator to let you know when you've neutralized it. It was pretty pricey too; ~$80 for a big bottle of it. If you do get into welding stainless a lot, and wish to use something like that, do read the MSDS and order a tube of Calgonate for your emergency kit. Many off the shelf stainless steel brighteners have similar formulations. But I digress... :)

Quote:

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Originally Posted by NRM

Redbeard-
I like your idea but I am going to use pull-pins (detent) to raise/lower the spit up and down equally.

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Ah, what you are doing makes perfect sense now. The first thing that popped into my head when I saw "stand" was one of those material rollers where unconstrained adjustment would be good.

Here is the progress from this weekend
I used the #4 copper wire b/c it was easy to clamp and with the aluminum I have I could not get it to clamp right.
Attachment 5437
Welded
Attachment 5438
Ended up being tighter than I wanted so I had to turn the inside tube down. I took it down ~.018"
Attachment 5439Attachment 5442
The outer tube did warp slightly so the fit is a little loose, but it will work.
Attachment 5443Attachment 5444
I also made some prongs to secure the meat to the spit
Attachment 5445Attachment 5446

I finished the stands this past weekend and I think that they will work. My only concern is the width of the base, next time I will make it bigger and use larger tubing.
Attachment 6909
Attachment 6910
Attachment 6911
Attachment 6912

Quote:

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Originally Posted by NRM

I finished the stands this past weekend and I think that they will work. My only concern is the width of the base, next time I will make it bigger and use larger tubing.

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Nice project you've got there. I especially like the prongs. Making my mouth water .... :D

I learned a lot from this thread - including pickling metal. Always nice to see a project unfold and learn something. Cheers!

Thanks Undercut. I have not had a chance to do the pickling step yet and some sopts need it. I hope its not to late.

Quote:

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Originally Posted by NRM

Thanks Undercut. I have not had a chance to do the pickling step yet and some sopts need it. I hope its not to late.

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Somewhat off-topic ... did you change your avatar recently? Bloomin' big fish! :D

Quote:

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Originally Posted by NRM

I finished the stands this past weekend and I think that they will work. My only concern is the width of the base, next time I will make it bigger and use larger tubing.

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Glad to see someone else who completes projects in the same time frame as I do. :D Good on ya mate!

Is that hand cranked or will it be motorized?

Red I would like to complete projects sooner but I only have Saturdays to work on my projects. It’s hand crank only if the motor quits. Here is a link to the whole setup: http://www.everlastgenerators.com/fo...li-Huli-Setup)