need to chase the threads on a 1965 3hp 3502 lightwin crankshaft. Need original size/thread pitch and if this don't work what size smaller die to use, thanks.
7/16-20. Next size down would be 3/8-24 (fine) or 3/8-16 (course). OR, probably a metric somewhere in-between, which I'm not smart enough to answer without getting out the charts.
