G43 activates positive tool length offset compensation, instructing the CNC controller to offset the Z-axis position based on the physical length of the active tool stored in the tool table.
Engineering Specifications & Parameters
Code Type
Modal Offset Activation
Risk Factor
High (Mismatched H-code causes spindle crash)
Paired Codes
G43 (Activate), G44 (Negative), G49 (Cancel)
Registry Variable
H-Address (e.g. H01)
Safe Tool Change Routine
Always apply G43 immediately after a tool change (M06) and cancel with G49 before tool retract or tool change routines.
T01 M06 (Load Tool 1)
G90 G54 G00 X0. Y0. (Position at Part Zero)
G43 H01 Z50.0 (Apply Tool 1 Length Offset, move to Z50)
...
G00 Z100.0 G49 (Retract and cancel tool compensation)
Critical Safeguards
Verify that the H-code matches the active T-tool number to prevent catastrophic Z-axis collisions.
Frequently Asked Questions
What happens if G43 is omitted after a tool change?
The machine moves according to gauge line reference without tool offset, which almost always results in the tool crashing into the workpiece or table.
