Need help with tubes?

Most of my small projects have used inch square tube, comes in approx 7 metre lengths and I cut and weld to match the job.
When looking at a basic go-kart frame for my kids I thought I would try round both inch and 3/4" or even nearest metric sizes.
The idea was to reduce the cut and weld by bending or forming etc.
When I contacted a stockest I was asked what do I want steam tube, ERW or seamless hot rolled or cold rolled and I must admit to not knowing which one would be suitable at reasonable cost.
I have some steel pipe fixing that I would really say are cast and some nipples! (no jokes here please) that are very heavy walled steel, but going off these I would consider it very hard to be able to form or bend this stuff.
I have used the odd piece of electrical conduit at work but never had to bend it and have always assumed it had no great stength, I connot even remember if it was welded seam or not!
ERW being Electric Resistance welded would this lease a line down the pipe that would be tempered different to the rest, and does it really matter?
So can anyone please give advise on what I should be asking for it will be much appreciated.
Cheers
Adrian
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wrote:

ERW is fine for almost anything except pressure hydraulics where seamless drawn is probably the best thing to use.
The handles of our big mobile chargers are formed out of cold drawn IIRC, mainly as the CNC bender guy has it on stock as pipework is his main business:
(Protopipe in Coventry if anyone ever needs the services of such a company)
Most common box section seems to be ERW as well, just noticed that on some 50X50X5mm that we were playing with today.
Peter -- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web: http://www.oldengine.org/members/diesel
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Adrian Hodgson wrote:

The seam is always chilled a fair bit, and knocks the crap out of cutting tools if you need to machine the bore!

For your use ERW would be fine and by far the cheapest.
Was it you that donated the air chuck? I think so, well thank you very much, took it over today from Martin Perman.
Regards Wayne...
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On Tue, 29 Aug 2006 19:36:58 +0000, Wayne Weedon wrote:

Hi Wayne; Hope the air chuck and other bits prove useful to you.
Adrian
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OK, for the kids, you can use what comes along.

seamless rolled costs more. If cold rolled, even more. The cold rolled seamless ones are mostly precision tubes with tight tolerances.

It doesn't matter for bending, welding and cutting to length. It matters a bit when drilling / milling. But these tubes are a little pain anyhow to machine (except cutting).

Take the cheapest one. Hot rolled ERW.
Nick
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