G74 Left hand tapping cycle

LinuxCNC Tormach G-code · Mill

Feeds a left hand tap to depth with the spindle turning counterclockwise, reverses to clockwise, dwells and feeds out. Not synchronized.

Format

G74 X Y Z R [P] [L] F

Addresses

Address	What it does
`X Y`	Hole position
`Z`	Hole bottom
`R`	Retract plane where feed starts
`L`	Repeat count, used with G91
`F`	Feed rate
`P`	Dwell in seconds at the bottom

How it works

Modal, motion group. Cancel with G80 or another motion code.

Example program

G20 G17 G40 G49 G54 G80 G90 G94 (INCH, SAFE START)
T6 M6 G43 (.250-20 LEFT HAND TAP)
S400 M4 (CCW FOR LEFT HAND TAP)
G0 X1 Y1 Z0.5
…

The full 6-line example is in the app. Example is in inch. Check offsets and clearances first.

Watch out for

Start the spindle with M4 before the cycle.
F equals RPM times pitch. Use a floating or tension compression tap holder since motion is not locked to the spindle.
For true rigid tapping use G33.1 with a spindle encoder.

Related codes

G84 · G33.1 · G80

G74 on other controls

The same number can mean something different on another control.

Control	Meaning
Fanuc	Left hand tapping cycle
Haas NGC	Reverse tapping cycle
Mazak (EIA)	Reverse tapping cycle
Okuma OSP	Reverse tapping cycle
Mitsubishi M70 M80	Reverse tapping cycle
Brother Speedio	Left hand tapping cycle
Siemens 840D 828D	Reference point approach
Fagor 8055 8065	Home search
Mach3 Mach4	Left hand tapping, Mach4
Centroid CNC12 Acorn	Left hand tapping cycle
Hurco WinMax (NC)	Left hand tap (ISNC) or single quadrant arc (BNC)
Fadal	Left hand tap
Swiss (Citizen Star)	Face peck drilling and grooving cycle

Every G-code for LinuxCNC Tormach in your pocket. The app has the full example programs, search by number or shop word, a line decoder and calculators for tapping, threading and drilling.

Open G74 in the app All LinuxCNC Tormach G-codes

App Store Google Play