CNC Machinist Calculator UltraG74 Left hand tapping cycle / Face peck drilling and face grooving cycle
Fanuc G-code · Mill, Lathe
On mills: Left hand tapping cycle
Taps a left hand thread. The spindle runs counterclockwise going in, reverses at the bottom and feeds out.
Format
Addresses
| Address | What it does |
|---|---|
X Y | Hole position |
Z | Hole bottom |
R | R plane where feed starts |
P | Dwell at bottom and R plane, milliseconds |
F | Feed rate, RPM times pitch in G94 |
K | Number of repeats |
How it works
Modal, group 09. Cancel with G80 or any group 01 code.
Example program
G90 G54 G00 X1. Y1. S400 M04 (SPINDLE CCW)
G43 H06 Z1. M08 (CLEARANCE)
G99 G74 Z-.6 R.2 F20. (20 IPM EQUALS 400 RPM TIMES .05 PITCH)
…
The full 5-line example is in the app. Example is in inch. Check offsets and clearances first.
Watch out for
- Start the spindle with M04 before G74 for floating tapping.
- With M29 before the cycle it becomes left hand rigid tapping.
- Feed override is fixed at 100 percent during the cycle.
On lathes: Face peck drilling and face grooving cycle
Pecks along Z with chip breaking retracts. With only Z it peck drills on center. With X and P added it cuts a wide face groove in steps.
Format
Addresses
| Address | What it does |
|---|---|
R (first block) | Retract amount after each peck |
X Z | End point. Leave X out for center drilling |
P | X step between plunges, radius value, no decimal point |
Q | Peck depth in Z, no decimal point |
R (second block) | Relief at the bottom, leave out for drilling |
F | Feed |
How it works
Non-modal.
Example program
G97 S1200 M03 (CONSTANT RPM)
G00 X0 Z.1 M08 (ON CENTER)
G74 R.02 (RETRACT .02 PER PECK)
…
The full 6-line example is in the app. Example is in inch. Check offsets and clearances first.
Watch out for
- P and Q take no decimal point. In inch, Q2500 is .25.
- For drilling, start at X0 and leave out X, P and R on the second line.
- The retract is small, so chips may pack in deep holes.
Related codes
G84 · G84.3 · G80 · G98 · G99 · G75 · G83
G74 on other controls
The same number can mean something different on another control.
| Control | Meaning |
|---|---|
| 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 |
| 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 |
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