Z-axis design - help sizing materials please!

[Jonathan]

The postage is the same as the product..........£120 would get you a nice linear rail system from gary at zapp or if you are patient then wait for S/H linear rails not supported round rail crap for that price....

Is gary going to stock NSK SH rails then or have I misinterpereted the 'S/H'?

I sent a message to the seller and got this:

Dear Jonathan,
2 SBR16-600mm supported rails +4 blocks:
92 usd
Air shipping cost is included.
===============
2 SBR20-600mm supported rails +4 blocks
109 usd
Air shippping cost is included.
Thanks!
Chai

So that's £70 for the 20mm or £60 for the 16mm. I may as well get the 20mm for the sake of £10. Are you saying these rails wont be any good quality? They're the same part numbers and dimensions as the ones at Zapp...they look the same as far as I can tell.

I've just looked at the 'HGR20' profile rail from Zapp. It comes to £129 for 2x600mm rails and only two blocks. I simply cannot afford to spend that much on rails!

I bought my 300mm Z axis profile rails, and my 700mm Y axis profile rails from Korea. FA system:
http://stores.ebay.co.uk/FA-SYSTEM_L...34Q2ec0Q2em322
And very pleased with them. Wouldn't contemplate buying these things new because of the price.

There's a good set of 590mm listed, but still £135 plus the tax is too much. I don't wish to sound as if I'm neglecting all your good ideas purely due to cost, it's just even spending £70 on the Z-axis is a bit much for me but I can see that it's worth it to get supported rail!

If you go with open bearings on an unsupported rail (or supported) remember that under certain load conditions they will 'open up' to some degree. Thanks to Ross for pointing out that obvious fact to me some time ago! There's alot to think about, or blissfully ignore!

I see, thanks for pointing that out to me! I'm still interested in the drilling option but it hardly seems worth it for the Z-axis now.

If I decided to use the supported round rail for the Y axis (or just round rail supported with the holes etc) is 16mm going to be sufficient or should I go for 20mm?

Also, how to I work out the optimal spacing for the rails on the Y axis? Is the torque from the Y screw a significant factor here since that would suggest I should put the rails close together?

Thanks again for all the advice - there certainly is a lot to think about!!