I think Mark made the wise comment. Look at the gauges the operating pressures are very low on the scale for R-22 and difficult at best to be accurately read. many of the R-410A gauges have 20 PSIG marks on the high side. That leaves an awful large interperatation when looking at R-22 saturation temps. The other kicker may be oil but worse yet refrigerant. Your gauges always have refrigerant in them, they will purge for 20 minutes when disconnected. Why subject your equipment to that?

Get a set for each and be done with it.