[QUOTE=jpsmith1cm;9980312]The biggest reason that you cannot use R410 gauges with R-22 is a matter of resolution. Hard to get an exact pressure reading on R-22 with a gauge that is calibrated for R410.
I know you can prevent contamination and mixing refrigerants if you do things right, purging, etc., which I always do. But why make combination gauges for R22 and R410 when, like you said if the gauge set is calibrated for one or the other you probably wont get exact readings. I'm sure there are new techs that don't purge correctly which can cause some problems when working with both out of the same set. Thats what my original post was eluding to.