Straight Turning
Reducing the diameter of a workpiece to a specified size.
Process Steps
1. Workpiece Preparation
Select appropriate stock material and ensure ends are squared. Mark the workpiece for required lengths and diameters.
2. Tool Setup
Mount the turning tool at center height and ensure it's properly secured in the tool post. Position it perpendicular to the workpiece.
3. Speed Selection
Calculate and set the appropriate cutting speed based on workpiece material and diameter. Start with conservative speeds for safety.
4. Initial Turning
Begin with a light cut to establish the desired diameter. Check measurements frequently during the process.
5. Final Sizing
Make finishing cuts with light depth of cut to achieve final diameter and desired surface finish.
Material-Specific Guidelines
Mild Steel
- • Most forgiving material for general turning
- • Produces continuous chips - use chip breakers
- • Good surface finish achievable with proper speeds
Recommended Speeds: 90-100 surface feet per minute for HSS tools, 300-400 SFPM for carbide
Tooling Notes: HSS tools work well, carbide preferred for production work
Stainless Steel
- • Work hardens easily - maintain constant cutting
- • Higher cutting forces required
- • Heat buildup can be significant
Recommended Speeds: 60-70 SFPM for HSS tools, 150-250 SFPM for carbide
Tooling Notes: Sharp tools essential, positive rake angles recommended
Aluminum
- • Gummy material - requires sharp tools
- • Built-up edge common at low speeds
- • Excellent surface finish possible
Recommended Speeds: 200-300 SFPM for HSS, 500-1000 SFPM for carbide
Tooling Notes: Polished rake faces help prevent built-up edge
Quality Control Specifications
Diameter
Method: Micrometer measurement at multiple points
Tolerance: ±0.001" typical
Frequency: Every part, multiple locations
Surface Finish
Method: Visual and profilometer check
Tolerance: 32-63 microinch typical
Frequency: Sample basis and 100% visual
Concentricity
Method: Dial indicator check
Tolerance: 0.002" TIR typical
Frequency: Setup and periodic checks
Length
Method: Digital calipers or depth micrometer
Tolerance: ±0.005" typical
Frequency: Every part
Operation Difficulty
Basic
Safety Guidelines
- • Always wear safety glasses and avoid loose clothing
- • Ensure proper tool height alignment with the workpiece centerline
- • Remove the chuck key before starting the machine
- • Never leave the lathe running unattended
- • Use appropriate cutting speeds and feeds for the material
Required Tooling
Right-hand Turning Tool
The most common turning tool, used for reducing the diameter of the workpiece
Center Drill
Used to create center holes for supporting long workpieces
Digital Calipers
For measuring the workpiece diameter during turning operations
Chuck
3 or 4 jaw chuck for holding the workpiece securely
Troubleshooting Guide
Poor Surface Finish
Check cutting speed, feed rate, and tool nose radius. Verify tool is sharp and at center height
Dimensional Variations
Check for tool wear, machine backlash, and workpiece deflection. Use tailstock support for long parts
Chatter
Reduce tool overhang, increase rigidity with tailstock support, adjust speed/feed rates
Taper in Long Parts
Check headstock/tailstock alignment, use steady rest for long parts
Tool Life Issues
Verify proper speeds and feeds for material, ensure adequate cutting fluid
Pro Tips & Tricks
Tool Height Setting
Use a center gauge against the workpiece to set tool exactly at center height. Incorrect height affects diameters and surface finish.
Best for: All turning operations, especially critical for finishing cuts
Tailstock Support
Use tailstock support for any length over 3 times diameter. Calculate proper center drilling depth for length of work.
Best for: Long workpieces and precision turning
Speed Calculation
Use the formula: RPM = (CS × 4) ÷ D, where CS is cutting speed in SFPM and D is diameter in inches. Adjust down 20% for roughing.
Best for: All turning operations, especially when changing diameters
Chip Breaking
Program or manually vary the feed rate slightly to break chips on materials that form long strings.
Best for: Deep cutting operations and stringy materials