Not a direct fit. Joining 3 inch camlock coupling to 3" NPT (National Pipe Taper) needs a 3 inch camlock to 3-8 NPT threaded adapter. Sealing method, the real-world trap, and the exact part to use.
Updated 05 September 2026.
Connect 3 inch camlock coupling to 3" NPT (National Pipe Taper)
How to join 3" camlock (A-A-59326) and 3-8 NPT, and what stops it leaking.
Not a direct fit. Joining 3 inch camlock coupling to 3" NPT (National Pipe Taper) needs a 3 inch camlock to 3-8 NPT threaded adapter.
The part to buy
A 3 inch cam-and-groove coupling has no thread of its own, so it reaches a 3-8 NPT (NPT) port through a same-size threaded camlock adapter: a Type A male adapter or a threaded coupler carrying the 3-8 NPT thread on its back. That thread is a tapered, 60 degree form of 88.9 mm major diameter at 8 threads per inch and seals on the thread flanks with PTFE tape; the cam end then mates to its opposite 3 inch camlock half.
The 3 inch cam profile and the 3-8 NPT thread are two separate choices. A correct 3-8 NPT back thread still leaves you with the wrong front if the half you mate to is not the matching 3 inch cam type, so confirm both the size and the A-to-F type before buying.
Related connections
Questions and answers
Connect 3 inch camlock coupling to 3" NPT (National Pipe Taper)?
Not a direct fit. Joining 3 inch camlock coupling to 3" NPT (National Pipe Taper) needs a 3 inch camlock to 3-8 NPT threaded adapter.