Thread Identification
Being able to identify fittings really comes in handy when trying to marry up to parts of a pressure washer.
Thread forms come in all shapes and sizes, and this can be a little confusing at first.
We have compiled a thread identification chart below to help you identify any fittings you may have!
O.D = Outside Diameter
I.D = Inside Diameter
DASH Size – Common terminology in the hydraulic industry.
BSP (British Standard Pipe) Threads
| DASH SIZE | THREAD SIZE | MALE O.D. | FEMALE I.D |
| -2 | G 1/8″ – 28 | 9.6mm | 8.8mm |
| -4 | G 1/4″ – 19 | 13mm | 11.8mm |
| -6 | G3/8″-19 | 16.5mm | 15.3mm |
| -8 | G 1/2″ – 14 | 20.8mm | 19mm |
| -10 | G 5/8″-14 | 22.7mm | 21mm |
| -12 | G 3/4″-14 | 26.3mm | 24.6mm |
| -16 | G 1″ 11 | 33mm | 31mm |
| -20 | G 1.1/4″ -11 | 41.7mm | 39.7mm |
| -24 | 1.1/2″ 11 | 47.6mm | 45.5mm |
| -32 | G2″-11 | 59.4mm | 57.2mm |
Metric Threads
| TUBE SIZE | THREAD SIZE | MALE O.D. | FEMALE I.D. |
| 6mm | M12X1.5 | 12mm | 10.5mm |
| 8mm | M14 1.5 | 14mm | 12.5mm |
| 10mm | M16 1.5 | 16mm | 14.5mm |
| 12mm | M18 1.5 | 18mm | 16.5mm |
| 15mm | M22 x 1.5 | 22mm | 20.5mm |
| 18mm | M26X1.5 | 26mm | 24.5mm |
| 22mm | M30X2 | 30mm | 28mm |
| 28mm | M36X2 | 36mm | 34mm |
| 35mm | M45 X2 | 45mm | 43mm |
| 42mm | M52XX2 | 52mm | 50mm |
BSPT Threads
| DASH SIZE | THREAD SIZE | MALE O.D. |
| -2 | R 1/8″ 28 | 9.7mm |
| -4 | R 1/4″ – 19 | 13.1mm |
| -6 | R 3/8″ 19 | 16.6mm |
| -8 | R 1/2″ 14 | 21mm |
| -12 | R 3/4″ 14 | 26.4mm |
| -16 | R 1″ 11 | 33.2mm |
| -20 | R 1.1/4″- 11 | 41.9mm |
| -24 | R 1.1/2″ -11 | 1.8mm |
| -32 | R 2″ | 59.6mm |
NPT Threads
| DASH SIZE | THREAD SIZE | MALE |
| -2 | 1/8″-27 | 10.2mm |
| -4 | 1/4″ 18 | 13.5mm |
| -6 | 3/8″ 18 | 17mm |
| -8 | 1/2″ 14 | 21.2mm |
| -12 | 3/4″ 14 | 26.5mm |
| -16 | 1″ 11.5 | 33.1mm |
| -20 | 1.1/4″ 11.5 | 41.9mm |
| -24 | 1.1/2″ 11.5 | 48mm |
| -32 | 2″-11.5 | 60mm |
Thread identification is a great skill to have, giving you confidence in ordering online and assembling your own kit.
All the best!
Conrad @ AC
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