M84/M85: Lock/Unlock Spindle Speed & Feed Rate Override Pots
Use M84 to set both override pots to 100% and to prevent their adjustment. M85 cancels M84 and re-enables override pots.
NOTE: M84 is also cancelled with tool call (Tn), so to maintain the lock, put M84 on same line as the X and Z move immediately after the tool call.