Not to belabor the point, but I'm not sure what a 3/16" pipe plug is- no such thing as 3/16" pipe threads per ANS (American National Standards), neither straight nor tapered.
I didn't mean to infer that it is definitely a tapered pipe thread, just that it seemed highly likely. It's possible that it is, in fact, a straight thread intended to take a bolt (maybe with a sealing washer). Can you get a good enough look at it to see whether it's tapered or straight? Or do you have a set of pitch guages to actually measure the threads per inch? 1/16 & 1/8 pipe are 27 threads per inch, and 5/16 & 3/8 NF bolts are 24.
I'd be leery of using a loose-fitting plug and depending on sealant to hold it. The use of a sealant with pipe threads is merely to fill microscopic gaps in the thread fit, not for retention of the plug.
Maybe someone with that exact same block can chime in here?
Last edited by Jack Gifford; 10-09-2006 at 02:42 AM.
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