G75 is a specialized CNC turning cycle designed for grooving operations that require controlled chip breaking. It is used for both OD and ID grooves and is especially effective in difficult materials like stainless steel, titanium, Inconel, and high-temp alloys where chips tend to wrap around the tool. G75 repeatedly advances and retracts the tool in small pecks, reducing heat, preventing chip wrapping, and producing a clean, stable groove profile. This makes it ideal for precise shoulder grooves, relief grooves, ring grooves, face grooves, and other tight-area operations.
1. Basic G75 Syntax (Modern Fanuc)
G75 R(retract)
G75 X(final dia) Z(end) P(width × 1000) Q(peck × 1000) F(feed)
Where:
- R → retract amount
- X → final groove diameter
- Z → groove end position
- P → groove width (in microns ×1000)
- Q → peck depth per pass (in microns ×1000)
- F → feedrate
Example:
G75 R0.2
G75 X42. Z-20. P300 Q200 F0.15
2. Real OD Groove Example
Cutting a 3 mm groove on a 50 mm shaft:
N100 G00 X50. Z1.
G75 R0.3
G75 X44. Z-6. P3000 Q200 F0.18
Meaning:
- Groove depth → 50 → 44 mm
- Groove width → 3.000 mm
- Peck depth → 0.20 mm
Tool pecks until entire groove is cleared.
3. Real ID Groove Example (Internal Grooving)
N200 G00 X32. Z2.
G75 R0.2
G75 X40. Z-12. P2000 Q150 F0.12
Perfect for small internal grooves where chip control is critical.
4. Face Grooving Example
G75 can also groove on the face (sideways direction).
N300 G00 X60. Z1.
G75 R0.2
G75 X50. Z-8. P2500 Q200 F0.20
This creates a radial groove inside a faced surface.
5. Breaking Down P and Q Values
P = groove width
Example: P3000 = 3.000 mm groove width
Q = peck depth
Example: Q200 = 0.200 mm per peck
Pro Tip:
For tough materials → Q = 0.10–0.20 mm
For aluminum → Q = 0.30–0.50 mm
6. Using G75 on Tough Materials (Stainless & Inconel)
G75 drastically reduces chip wrapping in difficult alloys.
Example:
G75 R0.15
G75 X27. Z-5. P1800 Q120 F0.10
This produces controlled chip formation and prevents insert breakage.
7. Common G75 Issues & Fixes
Groove out-of-round or tapered
– Check tool alignment
– Reduce feed
– Reduce peck amount Q
Chatter during pecking
– Increase R retract
– Reduce Q depth
– Increase spindle speed
Poor surface finish inside groove
– Add finishing pass with G70
– Use a wiper insert
8. Finishing Groove with G70 After G75
After roughing a groove with G75, use G70 for final finish:
G75 R0.2
G75 X40. Z-10. P2000 Q150 F0.15
G70 P300 Q400
This yields a clean, accurate groove profile.
9. Summary
G75 is an essential cycle for roughing and controlling chips during groove cutting, especially in deep, narrow, or precision grooves. Its pecking motion reduces heat, prevents insert failure, and ensures consistent chip formation. For 2025-level CNC turning where accuracy and tool life matter, mastering G75 is a major advantage.
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