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G74 Left hand tap (ISNC) or single quadrant arc (BNC)
Hurco WinMax (NC) G-code · Mill
ISNC: left hand tapping cycle, spindle CCW in and CW out. Add M29 first for rigid. In Basic NC G74 is single quadrant arc mode, cancelled by G75.
Format
ISNC: G74 X Y Z R [P] F [Q] [K or L]
Addresses
| Address | What it does |
|---|---|
X Y | Hole position |
Z | Hole bottom |
R | R plane |
P | Dwell at bottom |
F | Feed, RPM divided by threads per inch |
Q | Peck depth, rigid only |
How it works
ISNC: modal, group 09, cancel with G80. BNC: modal, group 01.
Example program
T7 M06 (.250-20 LH TAP)
G90 G54 G00 X1. Y1. S500 M04 (HOLE POSITION)
G43 H07 Z1. M08 (LENGTH OFFSET)
M29 (RIGID TAP ON)
…
G90 G54 G00 X1. Y1. S500 M04 (HOLE POSITION)
G43 H07 Z1. M08 (LENGTH OFFSET)
M29 (RIGID TAP ON)
…
The full 6-line example is in the app. Example is in inch. Check offsets and clearances first.
Watch out for
- Check the dialect of the file. The same code is a tap cycle in ISNC and an arc mode in BNC.
- If M03 is on, the control reverses the spindle for G74 by itself.
- Feed override is ignored and feed hold waits until the tap is out.
Related codes
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 |
| LinuxCNC Tormach | Left hand tapping cycle |
| Mach3 Mach4 | Left hand tapping, Mach4 |
| Centroid CNC12 Acorn | Left hand tapping cycle |
| Fadal | Left hand tap |
| Swiss (Citizen Star) | Face peck drilling and grooving cycle |
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