PCL Couplings & Adaptors

PCL has been designing and manufacturing couplings and adaptors for over 75 years. Within this section you will find the largest selection avaliable, from the standard Airflow range for fixed applications and Vertex for trailing hose, to the common industry interchanges and safety couplings.

Matching Couplings and Adaptors

Identifying couplings can be difficult , especially if there is no branding etched or printed on the sleeve - and when it comes to adaptors, different profiles do not interchange. For example, an XF adaptor will not fit into a Vertex coupling. 

Please see our ''actual size adaptor profile'' chart which enables adaptors to be matched to the outlines of those shown on the page.

The coupling can then be identified by establishing the adaptor that fits into it.

PCL couplings and adaptors are manufactured to conform to international standards and are interchangable with other manufactures' couplings and adaptors using the same standards. 

Jargon Buster

Couplings are often referred to as either ''females'' or ''sockets'' or ''couplers''.

Adaptors are often known as ''males'' or ''plugs'' or ''nipples''.

Nominal bore is the term used for the internal diameter of the hole that runs through the length of the adaptor. 

How to measure a Pipe Thread?

Thread sizes are based on trade size rather than actual dimension, which often leads to confusion. Here is our simple guide to measuring a thread and identifying it as a British Pipe Standard (BSP).

The BSP is the UK'S most commonly used type of thread and falls into 2 categories:

  • Parallel (BSPP) - Also known as G or Rp
  • Tapered (BSPT) - Also known as R or Rc

R, Rp and Rc threads are taken from BS21:1985 pipe threads for tubes and fittings where pressure-tight joints are made on the threads. Meanwhile G threads are taken from BS2779:1986 pipe threads for tubes and fittings where pressure-tight joints are usually made on a washer or 'O' ring.

Using a ruler or Vernier, measure across the outside diameter of a male thread. If the thread measures 0.5" it is not a 1/2" BSP thread. 

Using the table below you can see that a measurement of 0.5" is actually a 1/4" BSP thread and that a 0.75" measurement is a 1/2" BSP Thread. So, you can basically take 0.25" off your measurement to get the corresponding BSP thread.

Trade Size 


Threads per inch


Max Diameter Min Diameter
    Inch MM Inch MM
1/8 28 0.383 9.728 0.3372 8.565
1/4 19 0.518 13.157 0.4506 11.445
3/8 19 0.656 16.662 0.5886 14.95
1/2 14 0.825 20.955 0.7336 18.633
3/4 14 1.041 26.441 0.9496 24.12
1 11 1.309 33.249 1.1926 30.292
PCL Couplings & Adaptors