Shim- If your print calls for a 10-24 or a 6-32 scew than that is what you will have to use. You can not substitute a metric screw. Get yourself a Machinist Handbook or at least look up on google for
UNF and UNC threads. Any machinist or anybody selling screws or taps can supply you with a handy chart for the most common US threads. Be prepared - it is much more complicated than metric.