Timing belts and timing pulleys are the way to go, backlash free and reasonably quiet. I get mine from BSL or Brammer as they are now known but any bearing supply place would be able to get them for you if they dont have them in stock.
Hood

Thanks. I'll give them a google.

as promissed some pictures

X and Y are on the proper brackets, Z is still on a lash-up one day I'll get the time to finish that one
for now it works....

I got my belt bits from RS, not the cheapest but it got me going in a hurry

Some good informative pics there my friend thanks. Are they 12mm belts ? Have you thought about putting a solenoid on the oiler ? just something that came to me whilst looking at the machine it could be pulsed every programe run by mach and again at the end of a run.

The 600mm per minute max speed will traverse the 365mm table travel in around 36 seconds which I suppose is slightly on the slow side but still quick enough for me I can always upgrade to bigger steppers and ball screws if I found the speed a problem. Y axis is no problem of course at this speed having a much shorter travel. I was thinking of maybe going for a 10:1 on the Z axis as I get nervous when I feel the weight of the knee and table assembly. Do you think a 10:1 would make the Z too slow? I know the total travel of the Z is 360ish mm but in reality wouldn’t you only be using up to 100mm of that travel and for most applications even less. Am I right in that assumption? I’ve got lots of time to think about these things while I wait the long three weeks for my smooth stepper to appear from over the pond.
Thanks again chaps.

Hood. Any clues as to which belts and pulleys are suitable ? I can't find any timing belts on the UK brammer site. I've found a few at
http://www.bearingboys.co.UK/Timing_Pulleys-1042-c
But there are hundreds with different codes on that don't mean much to me. Some are pretty hefty in price as well IE over £300. What width of belt is likely to be adequate ? I was thinking 10mm but it's not obvious to me which of the ones on the site are 10mm. Hmmmm

I've had a look on the RS site to. They don't appear to be that overpriced the cheapest I could find was a company called HPC I'll have to give them a ring tomorrow as again whilst their site is a bit easier to navigate than most I'm still not sure what type of pulley and belt I need. WantCNC if you get a few minutes can you remember or have you got to hand which pulleys and belts you used in RS?

I think RS will be a lot dearer than your local bearing supplier, Brammers website is crap but they have helpful people at their local depots, well at least I have found that to be the case.
 I have a book at home that gives sizes etc and will look tonight and give you the codes for the ones I put on my Bridgeport (manual conversion one) That would be suitable for yours for sure.
 I just bought some 125mm Dia 14mm pitch 50mm wide for my new mills spindle, inclucding the taper locks I think I was around £50 but again will check tonight and let you know.

Hood

Wow 50mm wide that’s a chunky belt. I suppose it is the main drive so has to be good for a few horses. Some motor bikes use timing belts as the drive and by eye these are probably only a bit larger than 50 mm and are good for I dunno 60 Hp.
I've found a company called HPC gears on the net and gave them a phone. You give them the ratios, shaft sizes and power of the motors etc and they'll work everything out for you. The fellow got me thinking though he asked what the shaft speed of the Motors was.  I did a quick calc back from 600 mm per minute and came up with 600 RPM as there is a ratio of 3:1 and the lead screw is 3 mm per rev. This started me thinking at 800 pulses per rev this is only 8000 Hz’s. Is this a normal frequency to run these motors at i.e. are there torque problems trying to run them any faster. At 800 steps per mm of travel I have a resolution of 0.00125 mm per step so plenty fine enough for my set up. Should they run faster? Or am I missing something fundamental here?
WantCNC what is the restriction to 600 mm per minute I’m guessing it’s the torque curve and even though 600mm is fine for me I still like to know these things.
Thanks for looking Hood.

Yes its got to be a chunky belt, its a BIG AC servo I am putting on the spindle, 163Lb-in Continuus and 490 lb-in peak and dont want any mishaps LOL

Think your calcs are a bit screwed
 200 steps per rev x 10 microstepping (if you are indeed using micro stepping) = 2000 per rev, 3:1 gearing = 6000 thats 3 mm so 1 mm is 2000 steps per unit, 600mm/min at 2000 steps per unit = 600 x 2000 = 1,200,000 per min divide by 60 and thats  20KHz.

Not really sure what steppers will do but will work mine out and that will give you an idea (916 oz in on a Bridgeport Series 1 CNC) 2500mm/min Rapid speed, 5mm pitch screws so thats 500 rpm at the ballscrew, 2.5:1 gearing so thats 1250RPM at the motor. Think my calcs are right LOL

Just away to look see what size belts I got for the first Bridgeport I did.

Hood

Hood