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nexxo · 11-24-2002, 01:55 PM

The only problem is to convert those 20mm OD, 15mm ID pump connectors to 1/2" tubing... but that problem is easily solved.

Once reading up on the dark art of thread measurments, I found that NPT and BSPT thread measurements refer to the inside diameter of the connector, rather than (as you would logically expect) its outside diameter (= the internal diameter of the pipe it would fit into). D'oh!

Consulting a reference table (find one e.g. :here:) I found that 3/8" NPT or BSPT will do the trick nicely, accomodating a 15-16mm hole very well (as the threads taper slightly to ensure a good seal, it's OK for inside measurements not to be critically exact).

Despite having identical diameters, BSPT and NPT are not interchangeable, the former having a 55 degree angle between screw thread ridges, and the latter a 60 degree angle. This piece of knowledge is irrelevant to our application, of course; either will do. All we have to do is make sure we tap the inside of the pump connectors with the appropriate NPT or BSPT tap.

So: just get 3/8" NPT or BSPT to 1/2" barb threaded adapters, and that's it!

11-24-2002, 01:55 PM	#46
nexxo Cooling Savant Join Date: Jul 2002 Location: Brimingham, UK Posts: 385	The only problem is to convert those 20mm OD, 15mm ID pump connectors to 1/2" tubing... but that problem is easily solved. Once reading up on the dark art of thread measurments, I found that NPT and BSPT thread measurements refer to the inside diameter of the connector, rather than (as you would logically expect) its outside diameter (= the internal diameter of the pipe it would fit into). D'oh! Consulting a reference table (find one e.g. :here:) I found that 3/8" NPT or BSPT will do the trick nicely, accomodating a 15-16mm hole very well (as the threads taper slightly to ensure a good seal, it's OK for inside measurements not to be critically exact). Despite having identical diameters, BSPT and NPT are not interchangeable, the former having a 55 degree angle between screw thread ridges, and the latter a 60 degree angle. This piece of knowledge is irrelevant to our application, of course; either will do. All we have to do is make sure we tap the inside of the pump connectors with the appropriate NPT or BSPT tap. So: just get 3/8" NPT or BSPT to 1/2" barb threaded adapters, and that's it! __________________ "There is a thin line between magic and madness" Last edited by nexxo; 11-24-2002 at 02:11 PM.