Schedule 10 vs Schedule 40

The schedule number on pipe products relates to the thickness of the wall on the pipe: as the number increases, the thicker the wall thickness becomes. Also, while the schedule number can be the same on different sized pipes, the actual wall thickness will be different. 

ANSI B1.20.1 – NPT – American National Standard Taper Pipe Threads

NPT pipe threads – dimensions according ANSI/ASME B1.20.1/3.

• NPT – National Pipe Thread Tapered – is a U.S. standard for tapered threads used to join pipes and fittings is defined by ANSI B1.20.1 Pipe Threads

NPT threads may be referred to as MPT (‘Male Pipe Thread’), MNPT, or NPT(M) for male (external) threads, and FPT (‘Female Pipe Thread’), FNPT, or NPT(F) for female (internal) threads. Note that FPT and MPT are not authorized designations per the ANSI standard.