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.

[garry-in-michigan]

It’s happening again – my posts just disappear. Don’t let the eighth inch throw you – that’s the INSIDE diameter, the outside is much larger. Because of 80+ years of in and out ware (despite being coated with grease) the hole in the aluminium tends to get bigger, allowing the plug to go in farther. We made our own for racing by using the eighth inch pipe die to thread a brass rod. this was threaded into the gear case and carefully measured. it was then removed, cutoff and slotted. It was then put back in and filed smooth. When it started going in too far, we made another. If you retap the hole for a regular screw or bolt, you will have to machine a flat spot on the gearcase for a gasket to seal the opening.

• This reply was modified 4 years, 4 months ago by garry-in-michigan.

[green-thumbs]

Early Mercury K Models and Model A Ford
had several things in common…7/16″x 20 nuts and threads
and 1/8 NPT slotted brass plugs.
Anyway Bert’s is my source for Model A odds and ends
Louis

[rmhxruss]

Recessed allen hex is also available in a brass plug. common plumbing hardware store item.

[amuller]

It’s no skin off my teeth one way or the other, but you would be wise to take a look at any 1/8″ pipe thread fitting (any hardware store or home center) and see if this is not the thread you are looking for.

The nominal or “trade” sizes of pipes, tubes, and fittings often bear little relationship to actual measurements.

[dave-bernard]

If it does not have a recess for a gasket it would be a pipe thread . got a pic of the hole?

[hank1995]

Thanks again – yup – 1/8 ID and approx 3/8 OD. Braved black friday and picked these up at ACE this morning. I suppose you could go with a square head, cut off top, round it a little, and cut a slot for authenticity.

[Author]

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