Fitting box section inside of each other

[Thebeast]

Hi I have some ms 60mm box section @ 3mm thickness and need to fit some 50mm box section inside of the 60. Ideally if the 60mm box section had thicker walls they would slide inside tightly. How could I make this work with the available materials I have got?

I need them to be able to slide through the 60 mm box section with no wobble. Was thinking of welding 2mm flat each side maybe… any better ideas?

 

[minimutly]

You'll have to cut the larger one, grind off the weld bead, then weld it up again - without penetration..

 

[gaz1]

you can spot weld the 2mm onto the inner box section
or
but you can another sort of box section with no lip on the inside

if it has the internal lip you have shs

Cold formed square hollow section (SHS) is formed from hot rolled coil and has a smooth blue/grey coloured finish and a raised internal weld seam
but i cant remember its name

but if you are going to slide the tube often your better having a wear plate

 

[DAPPH]

What sort of lengths are you intending to telescope ? could a welded on made to measure be OK for the open end and a thin collar on the internal enclosed end do ?
You could also insert numerous phosphor bronze screws in the internal tube or onthe external tube so they take up any play by placing them every four or five inches on all sides along the length

 

[Tom O]

There are videos on YouTube that show how to make a internal cutter to travel along some threaded rod.

 

[Erie Fred]

Hi I have some ms 60mm box section @ 3mm thickness and need to fit some 50mm box section inside of the 60. Ideally if the 60mm box section had thicker walls they would slide inside tightly. How could I make this work with the available materials I have got?

I need them to be able to slide through the 60 mm box section with no wobble. Was thinking of welding 2mm flat each side maybe… any better ideas?

drill some holes in the 60mm for plug welds.
Plug weld your shims in.

 

[Gareth J]

There will be some play, it's inevitable.

Plug weld shims onto your inner bit of box but locate them so you don't have to grind off the seam on the inside of the 60mm

 

[Agroshield]

Plug weld shims onto your inner bit of box but locate them so you don't have to grind off the seam on the inside of the 60mm

Very good. By bridging over the seam, that avoids having to remove it. And on the seam axis, you could make the inner piece of box non-central (i.e. it rides directly against the opposite inside to the shim) and use a single 4mm shim either side of the seam weld.

With a 4mm shim, it could be held in place on the inside of the 60mm section without welding (4mm is thick enough to be drilled and tapped M4; the 3mm wall thickness of the outer tube would accommodate countersunk bolts for a smooth look).

In the other direction, weld or (countersink) rivet the 2mm shims to the outside of the inner piece.

It would be useful to know the orientation in which the assembly is to be used. If horizontal, the lower shim at the outer end might be better as UHMW plastic (see above gaz1 wear plate) so it can telescope easier (less friction).

 

[Mark 2]

You can weld the shims on the outside of the inner, just avoid the seam on the outer.

 

[RichardM]

Can you slide the smaller section in from either end? If so weld spacers onto one outer end of the smaller with a groove for the outer weld seam.

On the end of the outer, that the smaller comes out from, weld the spacers internally.

The inner slides in from the other end and the end spacers move along the outer as extended to retain alignment.


Have you thought about PTFE/ delrin/ nylon wear pads?

 

[gaz1]

you can also fit wheels onto the ends of each box section so that the steel can be rolled out easily instead of delrin wear pads

 

[Gareth J]

Very good. By bridging over the seam, that avoids having to remove it. And on the seam axis, you could make the inner piece of box non-central (i.e. it rides directly against the opposite inside to the shim) and use a single 4mm shim either side of the seam weld.

With a 4mm shim, it could be held in place on the inside of the 60mm section without welding (4mm is thick enough to be drilled and tapped M4; the 3mm wall thickness of the outer tube would accommodate countersunk bolts for a smooth look).

In the other direction, weld or (countersink) rivet the 2mm shims to the outside of the inner piece.

It would be useful to know the orientation in which the assembly is to be used. If horizontal, the lower shim at the outer end might be better as UHMW plastic (see above gaz1 wear plate) so it can telescope easier (less friction).

Have done it before. Might be a bit tight for space on 60mm but ought to be ok. Unless it's critical not to, I'd just shim up the inner and plug weld/grind.

 

[Kram]

What is the purpose or use for this telescoping tube? Will it have a bending stress, heat? How much load?

An option I like, is to drill conical holes on the inner peice upto the point of full extension - assuming a section will always be telescoped. In the holes, fit a load of greased ball bearings, it will give a smooth movement and take up the gap. The holes need to be drilled the same depth so best done on a drill press with a stop, rather than cordless. As you have a 4mm gap, thats 2mm each side. Use 4mm balls and drill the cone until they protrude just 2mm.

 

[Gareth J]

Coincidentally, had to use a shimmed box slider this evening.

The seam on the outer box plus actually on the LHS. Didn't realise that until afterwards