I made this tutorial so you won't make the same mistakes that i did.. It took me forever for get my nano watchband to be the correct size. The problem was that i was basing my measurements of the apple's specs page.. This is a bad idea.. you don't have all the measurements you need here.. you have to find the CADs page.
This is crucial since iphone nano watchband have to be down to the millimeters to look and work properly. That little tip right there would save you days!! your welcome...
Anyways, once you find the correct measurements you can build a 3d model or you can find one that has already been made.. scale it down to size and use it as a template to make your nano watchband
This is another crucial part you have to take notice. Programs export files at different sizes.. Maya said my item was 1 millimeter thick however, when i export it and import it into Shapeways.com it keep saying the item was huge and it would cost hundreds of dollars
The problem was that shapeways and maya had different ways to measure stuff.. i saw people using rhino and other programs and they had similar issues.. The way i was able to go around this .. in Maya i exported a small square that was 10 millimeters big.. when imported into shapeways.com it said it was 4 millimeters.. Therefore, .4 millimeters in maya = 1 millimeters in shapeways.. (note when picking what type of measurements pick inches)
That again took me couple of days to figure it out... the problem is that Shapeways.com will accept a model that is not thick enough in certain parts and will only let you know when they are canceling your order :(
Model your nano watchband.. create measuring squares to make sure is thick enough
Now the more complicated your nano watchband is the more you might have to worry about thickness.. You could manually check to make sure your thickness is the same everywhere. However, i found this website which actually will check the thickness for you.. this is incredible.. it saved me so much time. However, this website is way more expensive... So i decided to use shapeways.com (like i said these guys aren't giving me any money so if you know another cheaper place let me know :)
i hope this helps.. it will save you tons of work.. and if you use this to make your nano watchband.. please share your results