Turn Buckle Threads
I think that the idea of a machine screw instead of a cotter only makes sense on a very big boat where you mught be using 1/8" diameter cotter pins or bolts. Even there there are issues. The hole for the cotter pin should be very close to the jaw so that the jaws can not spread wider. If you use a bolt, the nut will need clearance in order to be free to turn which means that there will need to be more clearance than is normal for a cotter pin.