Jim, I'm pretty sure that was the tolerance number for rack/pinion's I'll have to check that number out and confirm it tonight when I get home.

Alot of spec's are available from bostongear.com they have some good online cataloges [ you have to register but thats the norm these days] as well as downloadable files for CAD.

I'm by no mean's an expert on this stuff compared to others on this forum, however if you do some search's on here you'll find a PILE of info on rack/pinion style systems. One fellow that's been especially helpful for me is 'Al' who's been there and done it himself.. Do some searchs! VERY good reading.

I've settled on a 12DP gear set and 6' long rack sections. I've also finalised my gearing to 5:1 reduction [ from the stepper down to the pinion] and hope to get a 0.003 per step resolution and then w/ micro stepping it will be a fair bit less than that. The real question is if the machine can produce those tight of a tolerance or not!

As Far as the plane is concerned.. they tell me it will get over 30mpg at over 200mph I've not flown ours yet so.. we'll see. Here's hoping! It'd be cheaper to fly out to the inlaw's rather than drive. Not to mention WAY faster

High Sea's;

If you look up Bostongear.com you'll find pretty much anything you want in the open gearing section. I have a local supplier of a different brand [ only because they came out 20% cheaper than ordering in the boston stuff] however most, if not all, of these gearing sizes are pretty standard and with some checking locally you should find a reasonable supplier. I'm planning to use 12DP gearing as it's been recommended to me by 'Al' [ he's on the forum] I had trouble getting the gearing spec'd for my application where I wasn't overloading my gearing past its 'rating'. 12DP seem's to be a good enough balance in size without being to weak or to course. You have to build some type of pre-loading to keep positive contact between the rack and pinion, otherwise you will end up w/ un-acceptable backlash. 'Al' recommends a "Rosta" tensioner however I'm planning on gas shock's due to my size/location and design. You'll have to provide some extra force to compensate for the tendancy of the pinion to want to push back out of the rack. There's some postings from a few days back that cover this.As I've mentioned to the other Jim, there's lots of good reading on the forum about this setup. Many people w/ more techical knowledge and exeriance than I, who's offered their advice and told their experiances.

Hope than helps.
Jerry