Reply To: LU Brass seal plugs

[frankr]

Pipe thread sizes are a relic from the past. In the old days when iron pipe was uses for plumbing, the pipe size referred to the inside diameter. Thus, 1/8 pipe is 1/8″ inside diameter. The O.D. is more like 3/8″. Don’t try to take any of these numbers to the bank though. Actually, 1/8″ pipe is more like 1/4″ I.D. Which brings up another point. The pipe was a bit larger then the nominal diameter to allow for rust build-up which would restrict the flow.

Anyhoo, the “3/8″ plug you are looking for is 1/8” NPT Pipe thread, or MIP, whichever you want to call it. MIP stands for Male Iron Pipe.