G84 Tapping Cycle

G84 is the canned cycle for tapping threads: it feeds to depth in time with the spindle, reverses the spindle, and feeds back out. The feed rate must equal the thread lead times the spindle speed so the tap tracks the thread.

Format

G84 X__ Y__ Z__ R__ F__ (F = lead x RPM)

How it works

  • The spindle and Z feed stay synchronized through the cycle, then the spindle reverses to back the tap out.
  • Feed must match the thread pitch; a rigid tapping head or tension-compression holder absorbs small errors.
  • G80 cancels the cycle.

Example

S500 M03
G84 Z-0.5 R0.2 F25.0 (1/4-20 at 500 rpm: 500 / 20 = 25 ipm)

Related: Tap Drill Chart and Thread Dimensions Chart.

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