Step By Step Measuring Threads
Thread & Connector Identification
How To Use This Section
BSP, Metric, American and Japanese thread sizes can be very similar. It is important to measure and match every criteria of thread diameter, thread pitch, seating or sealing type (including angle of seats if present) to accurately determine thread type.
Step 1. Investigation
- Europe ā Check DIN/BSP
- UK/Australia ā Check BSP
- America ā Check NPT/JIC/UNO/ORFS
- Japan ā Check JIS
All RYCO parts have a unique part number stamped on to aid identification.
Step 2. Visual Inspection
- Are threads parallel or tapered?
- Is there an O Ring or a washer seal?
- If cone seats are present are they concave or convex?
- Type and position on fittings
All RYCO parts have a unique part number stamped on to aid identification.
Step 3. Measure Threads
- OD of male threads
- ID of female threads
Using a thread gauge, determine the number of threads per inch.
If thread gauge is not available, measure pitch from crest to crest of adjacent threads, or count the number of threads in 1/4ā³ and multiply by four for threads per inch. Chart at bottom of page may assist.
Step 4. Seat Angle Measurement
Some fittings have dual seats (eg. JIC 37° & SAE 45°) and some have radiused cone.
Step 5. Conclusion
A final check can be achieved by mating with an actual coupling of the same thread.
ID

THREAD GAUGE

OD

SEAT GAUGE

TPI (Threads Per Inch) | 28 | 27 | 24 | 20 | 19 | 18 | 16 | 14 | 12 | 11.5 | 11 | 8 | 16.9 | 12.7 |
THREAD PITCH (mm) | 0,91 | 0,94 | 1,06 | 1,27 | 1,34 | 1,4 | 1,59 | 1,81 | 2,12 | 2,21 | 2,31 | 3,18 | 1,5 | 2,0 |