Reply To: Old and unusual screw sizes

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September 29, 2021 at 9:27 pm #247497
JOSEPH BRINCAT
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    One encounters 27 tpi on some pipe fittings, with out going down to the shop to measure, I’ll bet that that is a 1/8 NPS ( National Pipe Straight) as opposed to the common 1/8 NPT ( Tapered) , both are 27 TPI. I think that if you go to a lamp supply store , you will discover that the common threaded tube in most light fixtures is 1/8 (27 tpi) NPS

    AND yet another caution… careful that there is a British 1/8 pipe that is 28 TPI

    All this is great fun , and we haven’t even gotten into the metric and Whitworth stuff yet.

    Joe B