Knowledge Center
JIC Identification
JIC fittings are dimensionally identical to AN (Army-Navy) fittings, but are produced to less exacting tolerances and are generally less costly. SAE 45-degree flare fittings are similar in appearance, but are not interchangeable, though dash sizes 2, 3, 4, 5, 8, 10, 14, and 16 share the same thread size.
Measure the thread diameter with an I.D./O.D. caliper. … Use a thread pitch gauge to determine the number of threads per inch or the distance between threads in metric connections. Place the gauge on the threads until the fit is snug.
Metric to Standard
This chart shows typical standard and metric wrench or socket sizes for these standard fastener diameter sizes.
Fraction=Decimal=MM
Standard rational to standard irrational to millimeter irrational sizes.
NPT Identification
The rule of thumb when measuring National Pipe Thread is to subtract ¼-inch from your initial measurement. The thickness of the pipe wall will vary depending on the pipe, so always take that into account.
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Here’s an example: To measure the threads on a ¼ inch male pipe thread (MPT), measure the very outsides of the thread, then subtract ¼ inch of the outside diameter (OD) measurement to account for the thickness of the pipe wall on either side. When measuring a female pipe thread (FPT), measure the OD of the pipe itself and subtract ¼ inch to find the correct pipe thread size.
Perhaps even easier than this is to purchase a measuring tool called a caliper that will measure OD and inside diameter (ID).
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Additional Common Pipe Thread Acronyms
NPT National Pipe Thread (tapered)
FPT Female Pipe Thread (interchangeable with NPT)
FIP Female Iron Pipe (interchangeable with NPT)
MPT Male Pipe Thread (interchangeable with NPT)
MIP Male Iron Pipe (interchangeable with NPT)
IPS Iron Pipe Size aka"Iron Pipe Straight" non taper threads, usually requires a gasket to seal a connection (interchangeable with NPT)
PTF SAE Short Taper Pipe Thread
NPTF National Pipe Thread Fuel (American National taper pipe thread for dryseal pressure-tight joints)
NPSM National Pipe Straight Mechanical (American National straight pipe thread for mechanical joints)
NPSI American National Straight Intermediate Pipe Thread
GHT Garden Hose Thread
NST National Standard Thread (fire hose thread)
BSPT British Standard Taper Pipe Thread (metric)
U-Joint Identification
Using a few key measurements, you can find the correct u-joint. If the joint is mounted, you can use calipers to locate the u-joint before disassembly. Follow the guide in the link to get started, click "specification" (default is "Vehicle") in the Parts Finder section when the new window opens.
