Screws and backlash...personal choices

[~TM~]

OK, I'm working on my first build. It will hopefully end up having a table of about 4' by 5' usable area of 2.5' by 4' I'm using linear guides (dovetail type rails and linear bearings) The table will be constructed using 80/20 and a combo of 1/2" alum. plate and/or similar material. Now the question...
I want accuracy, speed, and repeatability. I know the difference between the two, so I guess I'll focus on accuracy. Should I use--

- 1/2" 10 5 start acme screw with dumpster nuts-- OR
-.631 dia .200 lead Nook ballscrew and single circuit nut

http://www.reidsupply.com/detail.asp...-304&ST=AR-304
http://www.reidsupply.com/detail.aspx?R=AR-314&ST=

The Nook ballscrew has an accuracy of .004" per foot according to the website (Is that with the ball nut, meaning the entire assembly has a possible backlash of .004" per foot?)
I don't know the accuracy of the acme screw though? Precision single start has around .003" per foot I've been informed so the question is which screw would everyone go with?
Any experience, insight, suggestions would be helpful. To be honest I'm on a budget ( like everyone) and surprisingly the prices are pretty close when you add up the screw, nut, flange, etc.
Thanks
~tommy

[ger21]

Originally Posted by ~TM~ I want accuracy, speed, and repeatability. I know the difference between the two, so I guess I'll focus on accuracy.

I count 3.

Keep in mind those are ± numbers, so worst case you could be off .008 in a 2 ft span. Speed and repeatability are probably easier to achieve. With accuracy, you're at the mercy of the screws accuracy.

The acme will probably be faster and have less backlash. The ballscrew will give you more resolution.

[~TM~]

yeah, : P sorry i meant between accuracy and repeatability. So i guess what you're saying is besides resolution (meaning smaller/more precise adjustments which in turn means better 'position' accuracy?) you'd probably go with acme screws unless i upgraded to a better ballscrew with a double track/nut right? And in that case the price rockets soooo, looks like McMaster is going to have a little business from me soon : )