It might have been better if jets were NEVER stamped!!! The reason, people drill them oversize. Best advice......NEVER believe what is stamped on a jet!
If these are genuine Rochester jets, Rochester would have stamped the size in thousanths of an inch. Thus a "56" would have originally been 0.056 inch.
A number 53 drill bit is, by definition, 0.0595 inch. Therefore, a 53 drill bit should not go through an unmolested 56 jet. Your "56" jet is at least a 59.
You will note your numbered drill index has gaps. These can be partially filled in by purchasing fractional metric bits.
Jon.
