Definition of Parting Off
Parting Off (also called cutting off) is a lathe turning operation used to separate a finished component from its bar or tube stock. The goal is precise separation, minimal tool deflection, and clean cut surfaces.
Not all parts require Parting Off—its necessity depends on the machining method, equipment, and raw material form.
When is Parting Off Required?
Applicable Scenario:
- Turning cylindrical parts from long bar or tube stock.
- Equipment: Conventional lathes, CNC lathes, or automatic lathes/Swiss machines.
- Example: Bolts, pins, bushings in mass production.
Not Required:
Parts separated by milling, casting, forging, or stamping are not considered Parting Off, even if material is separated.
| Manufacturing Method | How Part is Separated | Typical Parts |
|---|---|---|
| Milling | Saw or milling cut | Housings, brackets, irregular blocks |
| Casting/Forging | Flash/gate removal | Engine blocks, structural components |
| Stamping | Blanking/shearing | Washers, panels, casings |
| Advanced CNC Lathe | Sub-spindle transfer & separation | Complex shafts, small precision parts |
Note: “Parting Off” specifically refers to radial cutting on a lathe.
Step-by-Step Parting Off Operation
- Tool Setup & Rigidity
- Use a narrow parting insert (1.5–3 mm) and align tip with spindle centerline (≤0.05 mm deviation).
- Minimize overhang (≤3× insert width) to reduce vibration and breakage.
- Workholding
- Clamp length ≥1.5× workpiece diameter.
- Use steady rests/support rings for long parts; part catcher for short components.
- Cutting Mechanics & Cooling
- Feed the tool radially (plunge cutting).
- Apply high-pressure coolant (≥50–80 bar depending on material) for heat removal and chip evacuation.
- Reduce feed near the center (last 0.5–1 mm) to prevent tool tip damage.
- Post-Cutting Inspection
- Check cut surface for flatness, perpendicularity, and burrs.
- Apply light chamfering (0.2 x 45°) if needed.
- Verify dimensional tolerance (±0.05 mm).
Recommended Cutting Parameters
| Material | Cutting Speed Vc (m/min) | Feed f (mm/rev) | Cooling Pressure (bar) |
|---|---|---|---|
| 45# Steel | 150–180 | 0.05–0.08 | ≥70 |
| SUS304 Stainless Steel | 90–120 | 0.04–0.06 | ≥80 |
| Aluminum 6061 | 250–350 | 0.08–0.12 | ≥50 |
Adjust based on tool wear, chip form, vibration, and surface quality.
Common Challenges & Solutions
- Tool Breakage → Use rigid holder, reduce overhang, lower feed near center.
- Chip Entanglement → Use chipbreaker inserts, continuous coolant, adjust feed.
- Vibration/Chatter → Shorten overhang, use anti-vibration holder.
- Poor Surface Finish → Monitor tool wear, optimize feed and speed, perform light finishing.
Experimental Insight:
- Increasing coolant pressure from 30 bar → 70 bar doubled tool life and reduced surface roughness from 3.2 µm → 1.6 µm.
- Tool wear >0.15 mm increases roughness by 40%—replace promptly.
Key Takeaways
- Parting Off is critical for part quality, tool life, and machine stability.
- High-rigidity clamping, optimized cutting parameters, precise tool setup, and high-pressure cooling significantly improve results.
- Typical improvements from optimized operation:
- Tool life +1.6–2×
- Surface roughness reduced ~35%
- Dimensional consistency ±0.02 mm
FAQs
Q1: What is the cutting speed for 45# steel?
A: 150–180 m/min, feed 0.05–0.08 mm/rev, coolant ≥70 bar.
Q2: Can aluminum 6061 be parted on a conventional lathe?
A: Yes, 250–350 m/min, feed 0.08–0.12 mm/rev, coolant ≥50 bar.
Q3: Why do parting tools break?
A: Excessive overhang, improper feed near center, or insufficient cooling.
Baosheng specializes in high-precision CNC machining and lathe parting-off operation optimization, backed by years of industrial manufacturing expertise. Whether it’s tool selection, cutting parameters, or cooling solutions, we deliver professional customized solutions. Contact Baosheng today and let our engineering team help you enhance machining efficiency and part precision.
