[AT] Hydraulic fittings

[D8RMAN at aol.com]

I learned of BSTP threads when I couldn't get metric or SAE grease fittings 
 to screw in on a Japanese made excavator that had a couple of damaged 
fittings.  The threads were very close to metric but the pitch was different. 
Willard  Smith
 
 
In a message dated 8/15/2009 4:46:45 A.M. Pacific Daylight Time,  
jthall at worldnet.att.net writes:

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>>


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