Gee Two One: Machine Function Set Metric Units
G21Commands the machine to consider input programs as Metric Units
Syntax:
G21 this will cause the machine to see move and position entries in the program, as Metric Units
- G21 Can be seen as a “Declaration” code, used in the second line of your program along with any other codes you want to affect the entirety of what you are going or at the beginning of a canned cycle unit to affect only that unit (until changed by G20)
Caution: This in effect tells the control to see what your program has in it are Metric units, it’s a REALLY bad idea to stick in a imperial program and just try to run it G21. In general if you run Imperial then get into the habit of programming Imperial, same with Metric, if you run Metric then program Metric. Consistency is the key here.
Problems: if you have say Z-2. as a U-Drilling depth and you have used G21 that 2. will be MM’s NOT INCHES.
G21 Is A Modal Command