Converting american screws sizes to decimal
Most american screws (non-metric) under 1/4″ are named by their number and thread pitch (thread per inch). So a 10-32 and a 10-24 are the same diameter (#10), one is fine thread and one is coarse. To calculate the diameter you multiply the number by .013″ and add .060″. A #10 is therefore .060 + (10*.013) or .190″ (about 3/16″). I plugged the formula into a spreadsheet and calculated some common sizes.
Sure, you can look it up online or in Machinery’s Handbook, but if you know the formula (and even a lot of machinists don’t) you can calculate the screw diameter anytime.
