Nylon absorbs water.
It will shrink and grow with the weather causing it to bind if you require a sliding/moving fit.
You will need to have so much clearance that it will be a sloppy fit when "dry"
If you machine it across the grain it can crack, if it dries out it can crack, if you do both it will crack.
Other plastics can be used but you always get a trade off against other failure modes, elastomers are used in the suspension of cars for this reason along with natural rubber
Polyurethane can be bought in
different hardnesses shapes and lengths and fashioned on a lathe or Mill.
I take by wanting to make Nylon bushes you have access to this sort of equipment
2 secs on google found me this, although I have a supplier in West Sussex
http://www.bonaprene.co.uk/shop/13_Polyurethane_Tube__RodI suggest maybe looking at the quoted harness of Brands like Power flex and selecting where you want to go from there.
The softer you go the harder it is to machine, practice on a little bit first