[AT] Hydraulic fittings

[John Hall]

Lew and any one else who wants to know the difference between NPT and NPTF 
go to this site.

http://www.cutting-tool-supply.com/TechTips/Tapping/NPTvsNPTF/NPTVsNPTF.htm

To my knowledge it is impossible to tell the difference in the thread forms 
without inspection equipment (thread gauges). The differences are very 
small. I've made a lot of hydraulic components with pipe thread (most of 
ours used SAE ports) and they were all NPTF. Also they are always gaged when 
being made---no guesswork like you might do at home by counting the number 
of threads on the tap left above the part when tapping. We also use gages to 
check the depth we ream the hole prior to tapping. Properly machining NPT 
and NPTF components is a fairly involved process.

One other thing that has not been mentioned is BSPT threads---British pipe. 
I mention this for several reasons.
1) If it ain't built in the US, it may (probably) have BSPT fittings. This 
is especially true of Japanese equipment. It seems the British had a rather 
large influence around the globe once upon a time.
2) The thread pitch on BSPT is very close to the same size thread in US pipe 
threads.
3)BSPT use Whitworth thread form--which is slightly different than the 60 
deg used on most other threads, including metric.

Another good site to try when you are looking for thread information is 
www.marylandmetrics.com

John Hall

----- Original Message ----- 
From: "Lew Best" <lew at lewslittlefarm.com>
To: "'Antique tractor email discussion group'" 
<at at lists.antique-tractor.com>
Sent: Friday, August 14, 2009 3:14 PM
Subject: Re: [AT] Hydraulic fittings


This is something I've never heard of.  What's the difference?  How do you
tell which you have?

Lew Best near Waco, TX
Please note new email addy
lew at lewslittlefarm.com

-----Original Message-----

The first thing that is needed is knowledge of which type of fitting or
thread that you have. For pipe theads there are 2 common type in the US -
NPT and NPTF (for Fuel). They may go together, but they are different.
<<snip>>