Re: brass coupler pocket screw(s)


Kurt Laughlin <fleeta@...>
 

Do you have a micrometer (english or metric) that you could use to check the diameter of the thread on a mating screw? This diameter will always be slightly smaller than the nominal thread diameter.

Also, place a metric rule along the thread and determine the distance between thread crests (the wavelength, for the scientifically inclined). If very fine, measure distance of 10 crests and divide by 10.

There are a limited number of combinations of diameter and pitch that are standard. You might be able to divine the right one here: http://www.mcmaster.com/#machine-screws/=418ow2
or post and I'll take a try.

I would NOT use a tap to check the internal thread. With small sizes there are usually several closely spaced sizes. It is easy to change the thread while "checking". A tap can be used with a scew to check pitch, however.

KL

----- Original Message -----
From: Anthony Thompson

Does anyone know the metric screw size of the standard coupler
pocket screw in brass HO freight cars? I recently picked up some of
these cars second-hand and the previous owner lost or harvested the
screws. I do of course have some other cars which can furnish
examples, but don't have a metric thread checker. Thanks in advance.

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