Starrett Screw Thread Calculator on a Card
This is a very nice clean Screw Thread calculator marked "THE L.S. STARRETT COMPANY ATHOL MASS. U.S.A. PRINTED IN U.S.A." The calculator is two piece, the top round section spins, for finding sizes of tap drills for NC and NF, also NPT on the back side. They both are printed on a cardboard, or heavy card paper with a clear coating on each part, in good condition with some slight rubs and small light stains. The calculator has a brass center pivot in good condition. Although these were printed until the 1950's era, we believe this one to be from the 1940's. It measures about 3.2" x 4.55" with a 2.75" diameter round section. It's in nice shape! Much more rare than the Lufkin version of the same calculator!
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