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Know your pipe threads!

In Great Britain BSP British Standard Pipe threads are commonly used. These are either parallel (BSPP) which normally seal on a washer or 'O' ring seal, or tapered (BSPT) which taper along their length and normally seal by two mating threads.

How to measure your thread:

BSP Thread Measurement

Use a tape rule or (vernier gauge) to measure across the outside of the male thread. Note that a thread that measures 0.5" is not 1/2" BSP thread!

Using the table below we can see that 0.5" is actually 1/4" BSP thread. Similarly, a thread that measures 1.0" is actually 3/4" BSP thread.

 

BSP SizeMax. diametermin. diameterThread pitch
 mminchmminch(mm)        TPI
116" 7.723 0.304 6.561 0.258 28
18" 9.728 0.383 8.565 0.337 28
14" 13.157 0.518 11.445 0.451 19
38" 16.662 0.656 14.950 0.589 19
12" 20.955 0.825 18.633 0.734 14
58" 22.911 0.902 20.589 0.811 14
34" 26.441 1.041 24.120 0.950 14
1" 33.249 1.309 30.292 1.193 11
14" 41.910 1.650 38.953 1.534 11
12" 47.803 1.882 44.846 1.766 11
2" 59.614 2.347 56.657 2.231 11
12" 75.184 2.960 72.227 2.844 11
3" 87.884 3.460 84.927 3.344 11
4" 113.030 4.450 110.073 4.334 11
5" 138.430 5.450 135.472 5.334 11
6" 163.830 6.450 160.872 6.334 11

 

In Europe Metric (DIN) pipe threads are common on German machines. These generally have a 1.5mm thread pitch, although this can vary. Smaller sizes can be 1.0mm thread pitch, and larger sizes can be 2.0mm thread pitch. Other variations occur. French equipment often have GAZ fine threads with a 24 degree cone.

In North America NPT, JIC and ORFS pipe threads are common. Some NPT threads are similar to BSPT threads so if in doubt check origin of part.

In Japan JIS tapered and parallel threads are common and are interchangable with the respective BSPT and BSPP threads, although the 30 degree cones might be inverted.

 

Threads For Compression Fittings

Metric WADE

Tube OD (mm) 4 5 6 8 10 12 15 16 20 22
BSP Thread M8x1 M10x1 M10x1 M12x1 M16x1.5 M16x1.5 M20x1.5 M18x1.5 M27x1.5 M30x1.5
Max. Pressure 110 bar 110 bar 110 bar 110 bar 80 bar 50 bar 50 bar 50 bar 35 bar 35 bar

NB: The maximum pressure rating shown is for hydraulic applications. Pneumatic ratings are generally higher.

Imperial WADE

Tube OD 1/8" 3/16" 1/4" 5/16" 3/8" 1/2" 5/8" 3/4"
BSP Thread 1/8" 1/8" 1/4" 1/4" 3/8" 1/2" 3/4" 7/8"
Max. Pressure 103 bar 103 bar 103 bar 103 bar 69 bar 52 bar 52 bar 35 bar

NB: The maximum pressure rating shown is for hydraulic applications. Pneumatic ratings are generally higher.

Metric Nickel Plated Brass

Tube OD (mm) 4 6 8 10 12 15
BSP Thread M8x1 M10x1 M12x1 M16x1.5 M18x1.5 M22x1.5
Max. pressure  60 bar 60 bar 60 bar 60 bar 60 bar 60 bar

 

Metric Norgren/ Enots

Tube OD (mm) 4 5 6 8 10 12 15 16 18 22
Thread M8x1 M10x1 M11x1 M13x1 M15x1 M18x1.5 M22x1.5 M24x1.5 M26x1.5 M30x1.5

 

Imperial Norgren/ Enots

Tube OD 3/16" 1/4" 5/16" 3/8" 1/2" 5/8"
Thread 3/8"x24TPI 7/16"x24TPI 1/2"x24TPI 9/16"x24TPI 3/4"x24TPI

7/8"x20TPI

 

Conversion Factors:
1 bar = 14.5 PSI