[bilinghm]

My question is this, have those of you that have done conversions to X2 and X3 mills, especially those of you using kits like the CNC Fusion ballscrew kits, found that you can machine parts and maintain a tolerance of .001 or better?

This is to say, If you machine a 1” square, will it be within .001 of spec?

The Taig guys claim that their cnc machines will hold a thou, and this is with acme screws and brass split nuts. Will these conversions match this level of accuracy?

[ataxy]

yes you can as long as the assembly and adjustment of your conversion are well done also the way the machine is used will affect its precision so as long as you respect the capacity of your small machine you will be able to get result as good as there huge sister the result realy depends on the way the machine is worked on and the quality of the component and tool use on it

[Stepper Monkey]

It really has little to do with the type of screws used, and more to do with other things, not the least of which is the care in setup of the parts used to hold the screws such as the bearings and mounting blocks.
I'm a big fan of ballscrews, but they are not a magic guarantee of instant accuracy. Until you get those other things right even the most expensive ballscrews won't give you any real improvement. This is mainly why you hear of some ballscrew conversions with slop of many thou., or of acme or even standard thread screw kits holding 1 thou or so. Up to that point the screws just don't matter much, its all about your setup.

A lot of people just throw ballscrews in as a miracle cure, but it takes a lot of good setup to make them make a difference. I'm convinced that to some degree most of the improvement people see in their machines after installing a ballscrew conversion kit comes not from the screws or the kit, but just in the fact to install one requires someone to completely dismantle their stock machine and reassemble it with much care and lapping and fitting. That is where the real magic works.
This is probably why many people see just as much improvement using stock screws if they take the same care in setup. As you pointed out, Taig users seem to have a great deal of luck with that. Mainly I think you hear it from Taig people more often simply as they are forced to accurize the stock parts as they have no alternative - that machine has no ability to take ballscrews. Any other machine would probably fare just as well from a good setup using stock parts, it's just far less often someone takes the time to find out what they are capable of when there are new parts to try instead. My bone stock X3 pulls similar or better numbers than a lot of ballscrew converted X3's do simply because I completely stripped and rebuilt the thing and moved a lot of metal doing it.
Ballscrews are great and certainly convenient to have, but not necessary or required for accurate work to take place.