This should help you understand the metric tap conversion for rigid tapping.
1 inch = 25.4mm
M12 x 1.75 = 1.75mm per rotation
1mm = .039375
So take 1.75 * .039375 = .0689 per rev movement in inches
1/.0689 = 14.5137
So for an spindle speed of 14.5137 your feed should be 1ipm
You will need some surface speed to tap so lets spin 20 times that spindle rpm.
Rpm 290.2757
Feedrate 20ipm
But fadal controls like to manage feed rate more than crazy decimals of spindle speed.
So take 300/14.5137 (300 baseline rpm for this example) = feed rate 20.6701
FADAL FORMAT 2
M6T1
GOX0Y0
Z.2H1M8
G84.1G98Z-.7875R.2S300F20.6701
G80
M9
M6T2