# Joining ali tube.



## skipdiver (12 Oct 2017)

I'm a complete ignoramus with all things metal, so i thought i would venture over here to swarfland. :lol: 

I have asked this question before but i still haven't found a suitable answer. I need to butt join ali tube and i'm not sure how to do this satisfactorily. The easiest way and my preferred choice would be to use a small section of smaller diameter tube as a spline if that is the correct term? The tubing in question is 1 1/4" which has an OD of 31.75mm and an ID of roughly 28.5mm. The nearest size tube to fit inside is 1 1/8" which also has an ID of roughly 28.5 mm and is too tight to slide inside nicely. I'm wondering if i bought a mini lathe to take some off the diameter, what would i be looking at spending on one to get decent repeatable results? The pieces only need to be about 6 inches in length i think.

Is there a better way to do it? I've seen all sorts of tube inserts both metal and nylon but i really don't know which route to take and my brain hurts now from internet searches. This is not a one off and is something i will need to do regularly, so am looking for a permanent solution. Also forgot to mention that it needs to be able to be taken apart and put back together by the end user, so nothing too complicated. Maybe some way of screwing the two parts together.

Any ideas would be most welcome.


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## AndyT (12 Oct 2017)

You might be better off stretching the end of one piece so the other will sit inside it.

Try a search for "tube expander". You'll find an assortment of tools, hand-powered or hydraulic, designed to stretch the end of soft metal tubing, quickly and consistently. Most are for the smaller sizes used in plumbing, but I expect you will find something big enough. (It's not something I have experience of, I just know they exist.)

For example, this one is nearly big enough: https://youtu.be/nsHeIkF8Gyw


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## Rorschach (12 Oct 2017)

Considering the size difference I am sure the excess would just be filed or sanded off for a nice tight fit. You could also warm one and chill the other and get an interference fit.


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## skipdiver (12 Oct 2017)

Tried sanding and it takes too long, as well as being too inconsistent. Interference fit no good either as it needs to be able to be assembled and disassembled.

Stretching is a possibility, thanks.


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## sunnybob (12 Oct 2017)

Whats the finished item?
There wont be much strength sideways, especially if you weaken the ali by stretching.


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## kevinlightfoot (12 Oct 2017)

Could you use a wooden cylinder turned to a snug fit ,maybe oak and then use brass round head screws to hold the pieces together.A turner will easily make you a load in no time.


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## AndyT (12 Oct 2017)

I just remembered these people https://www.bpfonline.co.uk/search.asp?catid=3101

You'd want to phone them and check, but the threaded inserts look like they could be the answer, with a bit of studding glued into one side. 







Or indeed these:

https://www.bpfonline.co.uk/show_produc ... catid=2998


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## SteveF (12 Oct 2017)

could you cut slot on the inside one so that it compresses in outer one?


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## skipdiver (12 Oct 2017)

I forgot to say that i already have these fabricated by someone else and am looking to take over myself, as he is a bit unreliable, although he does a good job. He uses a piece of thicker gauge ali, 6 inches long, which he turns down to match the bars. I put my vernier on the joint piece today and it is 28.2 mm. 1 1/8" ali is 28.8, so i don't need to take a lot off. 

I also forgot to mention that the bars cannot be pulled apart as they have cloth attached but still need to be collapsible. That is achieved by the joint being a sliding one which can be retracted fully inside one bar, hence the need for a good fit. Not too tight, nor too slack. 

I am increasingly thinking that the best solution has already been reached and i am going to have to get a lathe and fabricate my own, though i know nothing of lathes and less about metalwork. Do like the wooden dowel idea though and that may well work. I will look into it. Splitting the tube is also something worth looking at. 

Thanks for the link AndyT. I had already seen those and had them in my basket at one time but that would mean that the attached cloth, which is currently held on with rivets, would have to change to a removable arrangement, possibly press studs and that changes everything again.

Thanks for all the ideas chaps. i will have another search but can anyone tell me what sort of money i would need to spend on a lathe to get something decent. I would only need small centres, so a mini lathe would suffice. If i fabricate my own, it would soon pay for itself.


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## TFrench (12 Oct 2017)

If it's going to pay for itself, I'd just get yourself a mini lathe with a decent guarantee and a set of insert tooling. Minimum set up time, don't have to learn to grind tools, it'll instantly start paying for itself.


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## skipdiver (12 Oct 2017)

Cheers. Any recommendations?


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## TFrench (12 Oct 2017)

I've never used a mini lathe, but the SIEG ones get consistently good commments. Think Axi do one, and arceurotrade. I got my dad a set of indexable tools from RDG that he loves.


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## skipdiver (12 Oct 2017)

Thanks, will check them out.


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## Rorschach (12 Oct 2017)

If you go with insert tooling make sure you get tips designed for aluminium, if you use steel tips you will make one heck of a mess.


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## skipdiver (12 Oct 2017)

Ok, thanks for all the info. Will research before i proceed.


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## skipdiver (19 Oct 2017)

Right, been looking at mini and micro lathes for metal and as usual, the more i look, the more baffled i become and it doesn't help that i am a complete ignoramus with all things metal and haven't used a lathe since i was at school 40 years ago and that was a wood lathe.

I need to turn 6 inch lengths of 10g ali tube down from 28.8mm to 28.2mm and that is it. I'm not interested in any other kind of turning and this is purely a means to an end for one process. I need to do batches of about twenty, 2 or 3 times a year. Something as small as possible because i don't have a lot of room and it will spend most of it's time under a bench. 

I have seen some micro lathes (there is a sieg one for sale near me second hand) but they are 125mm between centres. Is that the absolute limit, or is there a way to get a 6 inch piece done on one of those. Possibly doing one half, then spinning it round and doing the other? Does the tube need to be supported at both ends or just one end in the chuck? 

Can someone recommend a way to do this as easily as possible. Is a lathe the answer, or is there a simpler solution? I'm clueless and floundering.


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## ColeyS1 (19 Oct 2017)

How about hammer a threaded rod joiner in both ends ? Might be a bit of trial and error to find the right one- m20 ish perhaps ? Then threadlock in a short length of threaded bar and screw them together like a snooker cue. Perhaps a couple discreet grub screws might keep the threaded rod joiner in place or if it takes a bit of welly to hammer in, leave it at that.
Cheers
Coley

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## skipdiver (19 Oct 2017)

Thanks Coley but i can't do that. The two pieces of tube have cloth attached to them, so it's collapsible, which is done with a sliding joint, which goes inside the two tubes. There is no play to turn the tubes or pull them apart. I've exhausted every idea and the sliding joint is the only solution, so i have to find a way of reducing the tube by about 0.6mm, so it slides inside the outer tube. The nearest stock size is 1 1/8", which is 28.8mm and is a tad too big. I am happy with the way the thing works, but i currently pay someone to do them for me and he is a bit unreliable. I want to take over the operation myself but am not au fait with metalwork and lathes. Thanks for the input anyway.


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## J-G (20 Oct 2017)

The Seig C0 (I presume that is the model you are considering) does only have 125mm between centres and although you could probably remove the tail-stock to accommodate your 6" tube I would be much happier supporting the free end properly. 

Have you looked at the Osaki 300 which Cromwell have on special offer at the moment? I don't have any first hand knowledge of it but the spec is quite a bit better than the Seig with 250W motor rather than 150W, 300mm between centres which will easily accommodate your 6" (~150mm) tube and a 20mm head-stock bore (Seig has 10mm). It also has screw-cutting facility though this may not be of any interest currently - you never know what you may want to do in the future.


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## skipdiver (20 Oct 2017)

Thanks J-G. I had seen the Osaki on ebay but no idea of it's quality. We have a Cromwell Tool Store locally and i never thought of them, so that's a good reminder. Not being sure how lathes work, how is the other end supported? Is it a tapered tail-stock type thing? I don't know what is meant by head-stock bore, so that is something else to familiarise myself with.


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## J-G (20 Oct 2017)

I've done a quick schematic to show the various parts of the lathe. I've omitted the Cross-slide detail to keep it clear. It is to scale at the size of the Osaki 300.

The Head-stock bore is the hole that goes through the head-stock to enable longer lengths of material to be held - usually for making batches of small parts.

I would recommend supporting the free end of your tube with a chamferred bung which is also supported by a revolving centre. These are not supplied as standard so you need to buy the revolving (or 'LIVE') centre and make a support bung - from alum/steel/delrin/wood - it doesn't really matter what material you use, it just needs to fit on the open end of the tube and have a centre-drilled hole in the tail-stock side.

Naturally, in use, the tail-stock/Live Centre will be pushed up to the Alum tube - I've separated them so you can see what I mean.

You might also consider the Warco WM 150 which has a more powerful 450W motor though a smaller bore (11mm) and is currently £30 cheaper than the Osaki. I do have first hand knowledge of Warco - I have one of their milling machines - and can recommend.


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## ColeyS1 (20 Oct 2017)

Any chance we could get a little more detail of its application? 

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## skipdiver (20 Oct 2017)

Great info J-G, thanks. Funnily enough i was looking at the Warco last night and it's got £50 off at the moment.

Perhaps a picture or two would help with what i require.


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## J-G (20 Oct 2017)

skipdiver":18cft3fb said:


> Great info J-G, thanks. Funnily enough i was looking at the Warco last night and it's got £50 off at the moment.
> Perhaps a picture or two would help with what i require.


I was going to suggest a visit to the Model Engineering Exhibition on until Sunday in Warwickshire but Warco aren't listed as attending. Their web-site does say they are !!! Confused? you will be! If you did want to drive what I estimate to be the 80+ miles to the Warwickshire Exhibition Centre, I'd be happy to meet up and give you a 'hands-on' guide of the Warco and Chester offerings and the many other general engineering suppliers that you will no doubt need to deal with once you have a lathe  

The full details of the WM 150 spec., along with pictures, is at :
http://www.warco.co.uk/metal-lathes-met ... lathe.html


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## skipdiver (20 Oct 2017)

Thanks for that J-G, but i am working all weekend fulfilling an order. I will be using the last of the machined parts i bought in and will then have a while to sort out stuff before the next batch is due, so no hurry as yet. BTW, it's about 120-130 miles from here to there, dependant on route. My other half is from Rugby.


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## J-G (20 Oct 2017)

You're welcome, Steve. Sometimes opportunities are out of time.

I just did a quick 'Google Maps "Crow Flies" Measure' from WEC to Grimsby - that's why I put the '+'


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## ED65 (20 Oct 2017)

skipdiver":3cqycxfl said:


> The nearest stock size is 1 1/8", which is 28.8mm and is a tad too big.


Worth checking: is this the case with ali only? 

I don't know the market at all for tubing or rod but if the insert could be another material you could expand your search to SS, plain steel, copper, brass, plastics maybe and of course wood. 

If you have no choice but to stick to using the aluminium tube, at a 6" length you also don't need a lathe to do a small amount of turning-like tasks if you can rig up something with your power drill in a drill stand, or a pillar drill if you have one.


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## MusicMan (20 Oct 2017)

If you can't pull the tubes apart at all because of the cloth, I can't see how you will get the inner tube retracted into the outer tube. Could we have a pic?

You're in a bit of a quandary with lathe choice. I guess the method you are thinking of is to mount the tube in the headstock, pull out just over 6", support the end in a bung in the tailstock and turn down the tube then part it off. Not the easiest of operations in fact to get the tube centred accurately enough for this in a three-jaw chuck, so your accuracy will be limited. You could do it in a four jaw but there is extra setup time. Also, you have to get a lathe with a spindle hole big enough to to take a 28.8 mm tube. This pretty much rules out any micro lathe. Even my quite big Boley 4 would not do this. You are looking at something quite substantial and expensive. And you definitely want a power feed for the tool.

Possibly you would want to hold say 7" pieces in the three jaw (again with a bung at the tailstock end), turn down then part off. This would work well enough on a modest lathe but would waste material in the cutoff.

You could investigate centreless grinding, done by a third party as a service. The machine is fairly costly but once you have access to it, the process is very fast and will size the tube to great precision. There are services all over the place, e.g. https://www.westmidlandgrinding.co.uk/s ... -grinding/. I don't know the cost but expect it would be cheaper overall than an in-house lathe solution, because it would only take seconds to make one piece. You can probably get quite long lengths fed in at once, and cut them up yourself on a chop saw with metal cutting blade. The cheap Evolution chop saw would do it, but you do have to make a proper clamp to stop the tube rotating as it is cut. I suggest that you locate a centreless grinding service near you and go and talk to them.

Keith


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## SteveF (20 Oct 2017)

how about seat post shims (cycle) they make posts in different diameters as well
not sure what your paying and how long they need to be

i seem to remember being able to get in various sizes

Steve


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## MusicMan (20 Oct 2017)

An even simpler solution is to buy inner and outer tubes that are design to telescope and fit. In the sizes you mention there is

https://www.metals4u.co.uk/aluminium/c1 ... mm-(-1-14-)-od/p3057?showvat=true&gclid=EAIaIQobChMIhrLwz8z_1gIVIxbTCh3oRQhhEAQYASABEgJJV_D_BwE

Of course, I don't know the application or the tolerance that you need, but it's worth looking. Telescoping tubing is a very common need.

Keith


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## skipdiver (20 Oct 2017)

Thanks MusicMan, but i had already seen that and ruled it out. It is the wrong grade and gauge of ali. 

I've been looking for months on and off and i have come to the conclusion that the way they are made now is the way forward, so unless i can buy the correct diameter tubing off the shelf, i think i am going to have to learn how to turn it on a lathe. If anyone knows if and where i could purchase 28mm 10g ali, i would love to know. The only stuff i can find is 1 1/8", which is about 28.6mm give or take. That 0.6 is my nemesis.

I know you can get 28mm copper but it would not be strong enough and look daft anyway. I think you can get 28mm stainless but again it wouldn't look right and in a thicker gauge is very expensive. I have even contemplated 28mm hardwood dowel, but i'm not sure how stable it would be. May get a length and try it.


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## skipdiver (20 Oct 2017)

Sorry, didn't see the earlier post from you about the practicalities using a lathe to do what i want to do. I think i may just look around for someone else to make these small pieces for me. My town is over-run with engineering firms. There are scores of them.

SteveF, again i had already considered that but ruled it out. The joint is a sliding one because there is no play in the mating tubes to pull them apart or screw them together. They have cloth riveted to them which makes it impossible. The short 6" piece slides inside one tube, they are brought together and then slid back into the mating tube, before they are fixed. I really ought to take some photos, but i got busy and forgot. Only just finished for the day, so i will do it in the morning. A solution is waiting to be found i'm sure.


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## MusicMan (20 Oct 2017)

Have you rejected the centreless grinding route, then?

Keith


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## skipdiver (20 Oct 2017)

MusicMan":1ql0q9tg said:


> Have you rejected the centreless grinding route, then?
> 
> Keith



No. It was the tubing you linked to that i had already seen and ruled out. I don't know what centreless grinding is to be honest, so am about to have a search on the net.


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## skipdiver (20 Oct 2017)

ED65":31dto8vk said:


> skipdiver":31dto8vk said:
> 
> 
> > The nearest stock size is 1 1/8", which is 28.8mm and is a tad too big.
> ...



That would be great, if i could rig something up myself, but not sure how to go about it. I did put a piece in a drill and tried sanding it down, but it was very dusty and time consuming. I have a pillar drill, so that may be a possibility. Ali is soft and i don't need to take much off the diameter.


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## Jake (20 Oct 2017)

This site lists what looks like true 20mm tube on the basis that it specifies either an imperial or metric OD (don't know if the grade works for you)

https://www.doremetals.co.uk/aluminium/tube/


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## skipdiver (21 Oct 2017)

Thanks Jake but again, already checked them out. They have an incredible range of sizes and gauges in imperial and metric, but alas, no 28mm, which is the size i want.


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## Jake (21 Oct 2017)

Ah, sorry brain fade after reading. 

You've been through the tent pole analogy also (I feel like I also have,maybe your earlier thread)

http://rbjplastics.com/standard-profile ... ional.html


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## skipdiver (21 Oct 2017)

Yeah, looked at those too.

After much thought, i'm going to try some 28mm hardwood dowel and see how i get on with that. Stick to what you know, which in my case is wood.


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## Jake (21 Oct 2017)

Last idea I have is poke around on Alibaba and if you can stick a wanted ad up and see what comes out. I've only used it a few times but its worked out well each time, so if you can find someone offering machining services


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## skipdiver (21 Oct 2017)

Jake":11iftj4t said:


> Last idea I have is poke around on Alibaba and if you can stick a wanted ad up and see what comes out. I've only used it a few times but its worked out well each time, so if you can find someone offering machining services



Didn't know you could do that on there, so cheers for that. I did see some promising stuff on there, namely some hinged tube joiners, which would be great, but they were mostly for the boating industry and made of stainless, therefore prohibitively expensive.


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## ColeyS1 (21 Oct 2017)

Just looking for a piece of wood from the dog end rack. Spotted this leftover stop chamfered spindle





Even something completely square should fit snug inside. Knocking the corners off will prevent it wearing/working loose as easily.


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## skipdiver (21 Oct 2017)

Thing is, it needs to be loose as it is a sliding joint. I think a piece of waxed dowel may do the trick and it's available in the diameter i need. I'll try it anyway and see what transpires.


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## ColeyS1 (21 Oct 2017)

Are you gonna post a few pictures or is it too top secret :lol: 

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## skipdiver (21 Oct 2017)

ColeyS1":1h2slyvj said:


> Are you gonna post a few pictures or is it too top secret :lol:
> 
> Sent from my SM-G900F using Tapatalk



I was busy yesterday and forgot. I'm also a computer numbskull, so i would have to learn how to do it.


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