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This is related to my other question, but I have two steel tubes of different diameters (32mm below to 35mm top, respectively 1m and 45cm long). I don't have the tools to make a more precise measurement, but they look to be only between 1mm and 1.5mm thick. They look like this:

enter image description here

Question:

Is there a clamp or some cheap connector to connect vertically these 2 steel tubes of different diameters, so that they can be directly stacked upon one another? (One would extend the other).

The connection needs to be quite strong, probably be made out of steel too, otherwise it will surely break (the upper tube will have attached to its side about 15 kg). I wanted to find something close to this, but that actually works:

Different couplings

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  • what are the diameters and how long are the rods
    – asinine
    Nov 15, 2022 at 6:58
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    This sounds like an XY question. Please give clearer requirements in your other question rather than proposing a solution, and please stick to a single question.
    – KMJ
    Nov 15, 2022 at 7:01
  • @Ruskes thanks for the reminder, I added the length and diameters. @ KMJ, The main problem would be in the other question, but I'd like to know the answer to this question independently
    – flen
    Nov 15, 2022 at 7:41
  • from your other question I'm guessing that the steel poles are hollow. what size holes do they have.?
    – Jasen
    Nov 15, 2022 at 10:27
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    Rods and tubes are very different things. Please clarify which you are joining. A rod does not have a hole in the middle, a tube does.
    – Ecnerwal
    Nov 15, 2022 at 18:59

4 Answers 4

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If the smaller pipe fits inside the larger, that's a good place to start. A snug sliding fit would be ideal, but they can be looser. I reckon for this application you don't need to lock them together, just to set the height. For that a collar would do, then the upper pipe would rotate (probably a good thing), and could be lifted off.

I have bought industrial pipe clamps in both of these sizes (the smaller was actually for a customised monitor stand). I probably got them on ebay, where they're certainly available now.

But a 31.8mm seat post clamp for a bike (there are several common sizes, most smaller, but 34.9mm is also relevant) could be bent slightly bigger in this application as the load is so low compared to its intended use.

If you did want to lock the angle against rotation, and prevent lifting one pipe off the other, I'd use the pipe clamps I linked above, buying one of each size. Then I'd replace the supplied plates (2 per clamp) with 2 plates in total, each of which bridges between the 2 clamps, having 4 screw holes. I'd make these plates out of 4mm aluminium because it's easy to work.

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  • This is great, thank you! I think that's the solution, but I'm inexperienced and don't really know how to do it. I thought the pipe clamps' holes wouldn't align if they have different diameters? And would the seat post clamp work even if the connecting tubes (sandwiched inside the clamp) have different outer diameters? I just ordered the other tube and I believe the smaller one can fit inside the larger one. I'll test it when it arrives:) Oh, and what I'm trying to do is exactly connecting two different monitor stand poles! Thanks again for the answer!
    – flen
    Nov 16, 2022 at 0:11
  • The seat post clamp would clamp just the smaller pole to stop it going any further into the bigger. Insertion is essential. Even with the pipe clamps you'd either need to insert one pipe in the other or use 2 clamps per pipe and some rather beefy plates across the join. The outer dimension of those clamps goes up in steps rather than a constant wall thickness, so the similar ones I've used are the same externally for your 2 sizes. If you're unlucky a spacer plate would solve a mismatch
    – Chris H
    Nov 16, 2022 at 7:06
  • I'll try to get the chance to add a sketch
    – Chris H
    Nov 16, 2022 at 7:07
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The old Egyptian method.

Since you have no drill, but only a hammer.

Let's wedge it.

Slip the 35 over the 32 about 2-3 inches.

Make a mark so you know it is not moving.

Get some 1.5- 1.6 mm nails two inches long.

Speed 3 or more nails evenly around and start hammering (evenly around)

During the hammering process keep the 35 on the floor, so it has nowhere to go. Hold the 32 in the marked position.

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  • Good to know this! So just by nailing you can make the holes? But even if it's a steel pipe? Ideally I'd like to be able to disassemble it later if possible, but if there's no other solution I might pick this one. Thanks!
    – flen
    Nov 16, 2022 at 4:44
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    Not on the floor - on scrap wood on the floor. You'll damage the floor otherwise.
    – Chris H
    Nov 16, 2022 at 7:08
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    @flen You are not making any holes, insert the nails in the gap between the two rods, then hammer it in
    – asinine
    Nov 16, 2022 at 15:55
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DIY method

Wrap some aluminum foil around the 32 mm rod just enough so you can slide the 35 over it so it does not wiggle. The foil is just a space filler, it has no structural strenght.

You could use the self adhesive duct aluminum foil so it will hold in place.

While hooding the insert in place drill 2 holes in the overlap in the 32 rod part for screw insert.

Insert 6mm screws and tie with a nut from other side.

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    I'm not sure I understand your plan. Adding a sleeve to the smaller tube brings it to the size of the larger tube. How would they then be connected? Please revise to add more words.
    – isherwood
    Nov 15, 2022 at 13:59
  • I'm having a hard time visualizing aluminum foil being structurally strong enough to withstand any amount of lateral forces.
    – FreeMan
    Nov 15, 2022 at 14:09
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    @FreeMan I think the foil is a shim to make the gap smaller, then once you have a sliding fit, just bolt insert one into the other and cross-bolt.
    – Chris H
    Nov 15, 2022 at 16:45
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    Short sentences. No explanation. Confusion.
    – FreeMan
    Nov 15, 2022 at 16:47
  • Thank you for your answer! Drilling holes would indeed be a good idea (apart from some possible jitter, minimized by the foil, just as you mentioned), but unfortunately I lack the tools and knowledge for that. If possible, I'd prefer an option that doesn't need drilling
    – flen
    Nov 15, 2022 at 23:58
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I would procure a steel rod that just fits inside the smaller tube--maybe a threaded rod since they're readily available. I'd then load the joint up with epoxy and glue the bugger together. Lay it flat on the ground against a wall and shim the small end up to get everything straight. It'll be plenty strong for a display mount.

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  • 1
    Thank you! That's a creative solution, but I wonder if the epoxy will hold, I'm expecting to have a lot of force there, because an arm will be connected to the upper tube and will exert more force (is this the right term? From the leverage from having it extended and having a lot of weight attached to the other end) than if there was simply more weight on top
    – flen
    Nov 16, 2022 at 0:02
  • It absolutely will. It's contained by the tubing in compression.
    – isherwood
    Nov 16, 2022 at 13:38

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