G43 Tool Length Compensation

G43 applies a tool length offset so Z moves reference the part surface instead of the spindle face. Each tool measures a different length, and its offset lives in a numbered register called with an H word.

Format

G43 H__ Z__ (H = offset register, usually the tool number)

How it works

  • Store each tool length offset in the control, then call G43 with the matching H number.
  • Activate it on the first Z move after a tool change.
  • G49 cancels tool length compensation.

Example

T01 M06
G43 H01 Z1.0 (apply tool 1 length, rapid to Z1.0)

Related: G28 and Setup & Workholding.

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