Due to a bent Y axis leadscrew I want to replace with a ballscrew as I mainly do PCBs so need accurate work. I also found that the Y axis was much slower than the X axis, so if ballscrews are less draggy I should be able to speed up a little here? But I don't want to at the expense of accuracy.

So, how do I work out what I need? If I measure my X axis leadscrew teeth per inch is that a valid measurement and can base my ballscrew pitch on that? As that speed is fine.

I take it that I get them to do the ends to suit my bearings and motor coupler? i.e. the whole thing is a custom length. And what's the most suitable ballnut for me?

I think linearmotionbearings2008 on ebay is a good seller - best to get from him?