Where can I get 1.25" tube?

[acey]

I'm looking for 1.25" aluminium or steel tube to make a focusser for a scope I'm building. Can anyone suggest a supplier?

[Bizibilder]

http://www.modelmakingsupplies.co.uk/alisttube.htm Should be a start for you - hope this helps - (usual disclaimer by the way).

[acey]

Many thanks - that's a help.

I realise from the searches I've been doing that tube is generally quoted by its external diameter, and of course it's the internal diameter that matters for a focusser tube. So if anyone can suggest a suitable standard size that would give me 1.25" internal diameter then that would be a big help.

My plan is to make a helical Crayford, so any kind of metal tube will do (and I don't need much of it). Alternatively I've heard of people making simple helical focussers from plastic plumbing parts so if anybody can offer input on that I'd be grateful.

[Bizibilder]

Tube is invariably given as outside diameter and wall thickness, as these are the dimensions that are held to close tolerence during manifacture. The 1.25" outside diameter by 16g (16 gague) tube is 0.064" (sixtyfour thousandths of an inch) thick so both walls add up to 0.128" - this is 0.003" (three thousandths) bigger than one eighth of an inch. So this tube will just NOT telescope (sorry about the pun!!) over a piece of "one and one eighth inch" tube (unless it is turned down by say 0.004").

Hope this helps.

[acey]

Cheers for that. I also found a site offering 1.5" 10g brass tube, but by my reckoning that gives an internal diameter of 1.244".

I'm wondering if maybe I'll need to use a telescope extension tube - probably end up the same pricewise.

I just Googled "telescope extension tube" - and came back to this posting!

[Merlin66]

Check out B&Q for plumbing fittings. The standard drainpipes used to be 1.25" so you could get an "extension" or "joiner" which would be 1.25 inside diameter.

The plastic fiitings are not so robust and tend to have tapered threads ie start loose and get tighter as they screw together.

I now use the Baader helical focusser for the spectroscope - check out the TS Baader page - there are many different adaptors etc available.

[Bizibilder]

Your tube at 0.244 is 0.006" too big. That is why you (and manufacturers) would use a couple of screws to grip the thing!!! (or cut a slit in the larger bore and "squeeze to fit").

[acey]

Thanks for these tips. My project is to convert my 8-inch dob into a travel scope, so I already have the focusser from that scope and could use it if need be - but I'm hoping for something lighter and simpler if possible, and a helical focusser appeals to me on both counts. Maybe I need to check out B&Q!

[Stardust]

Depending on the length and the wall thickness of the brass tube I might be able to open it out on my lathe for you.

[mattifor]

e-bay have some listed also.

h t t p://cgi.ebay.co.uk/Aluminium-Tube-1.1%2F4%22-%2F-30mm-od-x-1495mm-+-2-END-CAPS_W0QQitemZ280372248981QQcmdZViewItemQQimsxq20091113?IMSfp=TL091113175003r14760

[acey]

Thanks for these.

Stardust - I may get back to you on that - very kind of you to offer.

Mattifor - I can't get that link to work, unfortunately.

[mattifor]

Thanks for these.

Stardust - I may get back to you on that - very kind of you to offer.

Mattifor - I can't get that link to work, unfortunately.

Just take out the spaces in the http

[acey]

Tried that, and some other things. Oh well, thanks anyway.

[mattifor]

try his shop page eBay UK Shop - Aluminium Droitwich: Aluminium Chequer plate, Treadplate, Rod Round Flat Square Bar

then search for 1.1/4" aluminium round tube

Ivor

[acey]

Got it, ta - unfortunately too small.

Think for now I'll take the rack-and-pinion focusser off the dob and try that.