Taper/parrallel thread - what is the difference?

[neilmft135]

Are you aslking do you use ptfe tread tape with a certain type fitting. I use pipe fittings all the time on hydraulics and diesel engines. the main differance is not the fitting it is the appication on certain types of hydraulics you will use a parallel fitting to seal it a 0-ring or dowty seal is used. No tread tape nessecery, taper type fitting come in NPT or BSP
thread pitch per inch sliightly differant between the two npt popular in the oil industrie. On all taper type threads it is advisable to use ptfe thread tape or a thread paste to seal the joint. I hope this helps the appication of pipe threads could take a day to explain fully

 

[Amari]

Thanks mft. I had never heard of taper thread so was asking the meaning rather than what to wrap round, if at all. Grateful for all the replies but still a bit confused, almost wish I hadn't asked!

 

[Bejasus]

Both together - Tapered on the left, Parallel on the right.