1/2" to 3/8" adapter problem

[Jsandy]

I'm running a JD 4066R (open station) with a factory installed 3rd function that I normally use to run a grapple. The hydraulic connections on the tractor and the grapple are both Pioneer 4000 -3P series. (3/8" body with 3/8-18 NPTF threads). I bought a hydraulically angled snow plow for my FEL. I didn't check before hand but it arrived with 1/2" flat faced connections. I thought , "No problem" and bought another Pioneer 4000-3P connection set. I looked around and found a couple 1/2" female NPT to 3/8" male NPT reducers. I did some research and the NPTF threads are supposed to be compatible with NPT threads (just need to use teflon tape). When I went to dry fit them together the 3/8" male end of the reducer will only screw in about 3 threads (a little less than half way). It clearly is not bottoming out. I double checked (the reducers came from Graingers) the specs and the reducer is 3/8-18 NPT while the Pioneer connector orifice is listed as 3/8-18 NPTF. Since the NPTF (F stands for "fluid") is supposed to be compatible with NPT I can't figure out what is wrong. BTW I found a similar (different brand) reducer later at TSC and the same thing happened. It screws in 3 threads with 4 threads still showing. Any ideas? Thanks.

 

[RickB]

They are tapered threads. Three turns by hand sounds about right. Pick up a couple wrenches and turn them until they are tight.

 

[WranglerX]

Actually the "F" stand for fuel....

National Pipe Thread vs. National Pipe Thread Fuel

Dale

 

[Jsandy]

Thanks for the responses. A little more research led me to the same conclusion. I have some pipe dope with teflon and will wrench them together this morning.

 

[ericm979]

Loctite 545 for hydraulic connections worked better for me than the teflon pipe dope.

 

[TractorGuy]

For fuel and oil connections with pipe thread I use a drop of aviation permatex. Mainly because I have it on hand but also because it is resistant to both liquids.