Maho Overarm - 90mm Diameter Tube

I've decided that I'm going to have to make the horizontal overam for my Maho MH600 since the chance of finding one is slender. Fortunately
it shouldn't be too hard to make since the main component is a 90mm diameter steel bar. Using solid steel bar would be rather wateful (and enourmously heavy) so I'd like to use steel tube of some form. To give you an idea of the overarm the factory item is here
http://farm5.static.flickr.com/4072/4668401001_01cc659512_b.jpg
My version would end up with the round bar/tube running the full length with a couple of 1" brackets tig welded on. Suggestions welcomed as to what wall thickness would be appropriate would be appreciated along with any possible sources of a suitable length of tube.
Thanks
Charles
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Charles, will you perhaps have rigidity and vibration problems without the mass of a solid bar? At the very least I would fill it with a resin concrete with fine aggregate.
AWEM
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On Jun 4, 1:08 pm, "Andrew Mawson"

Andrew
Good observation. If I used a 6mm wall I'd expect that but I'm more thinking of a 15-20mm wall. That would take 30kg off the weight of a meter of 90mm which would be handy. Worth noting that the factory vertical heads are effectively mounted on thick wall tube since the head is driven from a gear on the end of the round bar deep inside the machine.
Charles
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Charles, you will find that 90mm thick walled tube is a lot more expensive than 90mm solid bar by the time it`s ready to be used. 90mm EN8 bright is running at roughly £50/metre + vat at the moment.We find it cheaper to bore solid than buy tube. We stock up to 120 dia in EN8 bright so could check how good it is for you. Macreadys have a depot in North London I think.Or you could probably buy ground bar quite easily. Mark.
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That's interesting. I wouldn't have supposed that tube would be a lot more expensive. Thanks Mark
I guess that I'll have to make a very large boring bar to go half a meter in!
Charles
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I made my own overarm for my Deckel FP1 and although a more conventional shape, I filled mine with concrete and had no trouble with rigidity and vibration, I would make yours from a solid bar with a hollow fabrication welded to it and then fill it with concrete. Peter
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