Purchasing pre-cut/pre-threaded pipe can get to be a bit costly. There is also no room for error or extra fittings that may occur in a piping project. The answer to resolve this issue is to thread your own.
Cutting a pipe can be done by any number of tools around the shop, but threading it requires a pipe threader.
The process is simple; secure the pipe, fit the die heads to the handle, then fit the die head to the pipe end and slowly twist. A simple kit like this one can be found for around $40 and features 1/4, 3/8, 1/2, 3/4 and 1″ pipe threading die heads.
Sample Selection/Street Pricing [Froogle]