Drill Bit Sizes Used For J-Head Nozzles

At one time, about 2 years ago, I used metric sized drill bits to drill the nozzle orifice.  It was discovered that these drill bits were drilling holes larger than the rated size.  For example, a 0.50mm drill bit would drill out a hole about 0.55mm in size.  I then made a decision to use slightly smaller drill bits in order to ensure that the orifice would be as close to the rated size as possible.  The drill bits used are as follows:

Orifice Size		SAE Drill Bit		Actual Metric Size
0.35mm		0.0135		0.343mm
0.40mm		0.0157		0.399mm
0.50mm		0.0189		0.480mm