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G76 Fine boring cycle / Multiple pass threading cycle
Haas NGC G-code · Mill, Lathe
On mills: Fine boring cycle
Bores to depth, stops and orients the spindle, shifts the tool off the wall, then rapids out so no drag line is left in the bore.
Format
Addresses
| Address | What it does |
|---|---|
X Y | Hole position |
Z | Hole bottom |
R | R plane |
Q | Shift amount, direction from Setting 27 |
I J | Shift amount along X or Y when Q is not used |
P | Dwell at the bottom |
F | Feed rate |
L | Number of holes for repeats in G91 |
How it works
Modal, canned cycle group 09. Cancel with G80.
Example program
G90 G54 G00 X0. Y0. S1200 M03 (BORE CENTER)
G43 H07 Z1. M08 (APPROACH)
G76 G98 Z-1. R.1 Q.01 F4. (FINE BORE, SHIFT .01 BEFORE RETRACT)
…
The full 5-line example is in the app. Example is in inch. Check offsets and clearances first.
Watch out for
- Set the boring bar tip so it points away from the shift direction after spindle orient, or it will scrape the wall.
- Keep the shift small. It only needs to clear the wall.
On lathes: Multiple pass threading cycle
Cuts a complete thread with one block. The control spaces the passes, infeeds at angle A and chamfers out at the end. Works for straight and taper threads, OD or ID.
Format
Addresses
| Address | What it does |
|---|---|
X | Minor diameter of the thread, final X |
U | Incremental X from start to final depth |
Z | End of the thread in Z |
W | Incremental Z length of the thread |
K | Thread height, radius |
D | Depth of the first pass |
F | Thread lead |
A | Tool nose angle, 0 to 120, no decimal point |
I | Taper amount, radius, negative for a normal OD taper |
P | Infeed mode, P1 to P4 |
Q | Thread start angle, no decimal point, for multi start threads |
How it works
Non-modal, group 00.
Example program
G99 G97 S800 M03 (FEED PER REV, FIXED RPM)
G00 G54 X.85 Z.3 M08 (START 3 PITCHES AHEAD)
G76 X.6274 Z-1. K.0613 D.012 F.1 A60 (THREAD .750-10)
…
The full 6-line example is in the app. Example is in inch. Check offsets and clearances first.
Watch out for
- Use G99 and G97 for threading. Do not use G96.
- Each pass depth is D times the square root of the pass number, so passes get smaller.
- Haas suggests A59 for 60 degree threads to reduce chatter. A and Q take no decimal point.
- Settings 95 and 96 set the chamfer out. M24 turns it off.
Related codes
G76 on other controls
The same number can mean something different on another control.
| Control | Meaning |
|---|---|
| Fanuc | Fine boring cycle |
| Mazak (EIA) | Fine boring cycle |
| Okuma OSP | Fine boring cycle |
| Mitsubishi M70 M80 | Fine boring cycle |
| Brother Speedio | Fine boring cycle |
| Fagor 8055 8065 | Probing move while touching |
| LinuxCNC Tormach | Lathe multi pass threading |
| Mach3 Mach4 | Fine boring, Mach4 |
| Centroid CNC12 Acorn | Fine boring cycle |
| Hurco WinMax (NC) | Fine boring with orient |
| Fadal | Fine boring with oriented shift |
| Swiss (Citizen Star) | Multiple pass threading cycle |
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