Frequently Asked Questions

using a caliper to measure BSP thread sizes

The image above shows the ‘Basic Major Diameter’ of a 1½” BSP thread

How to measure BSP thread sizes

The “Basic Major Diameter (mm)” can be obtained by measuring the larger thread diameter on the threads of your immersion – typically called the “across the thread” measurement.

The “Basic Minor Diameter (mm)” can be obtained by measuring the smaller thread diameter. This measurement will closely resemble the measurement on the “port” or “inlet” on the tank.

BSPBasic Major Dia. (mm)Basic Minor Dia. (mm)
1/16″7.726.56
1/8″9.738.56
1/4″13.1611.45
3/8″16.6614.95
1/2″20.9618.63
5/8″22.9120.59
3/4″26.4424.12
7/8″30.2027.88
1″33.2530.29
1 + 1/4″41.9138.95
1 + 1/2″47.8044.85
1 + 3/4″53.7550.70
2″59.6156.66
2 + 1/4″65.7162.75
2 + 1/2″75.1872.23
2 + 3/4″81.5378.58
3″87.8884.93
Contact Us

If you have any questions, or would like to speak to us about stocking our range, please leave your details and we'll be in touch shortly

Not readable? Change text. captcha txt

Start typing and press Enter to search