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Parting

Cutting off a completed part from the stock material using a narrow cutting tool. Requires proper speed and feed rates to prevent tool breakage.

Process Steps

1. Tool Preparation

Set up parting tool at exact center height and square to the workpiece.

2. Speed Setting

Set appropriate surface speed - typically 40-50% of normal turning speed.

3. Initial Groove

Start the cut with a good feed rate to establish the groove.

4. Maintaining Cut

Keep constant feed pressure, ensuring chips are forming properly.

5. Final Separation

Reduce feed rate as tool approaches center to prevent binding.

Material-Specific Guidelines

Mild Steel

  • • Good parting characteristics with proper setup
  • • Continuous chip formation requires attention
  • • Cutting fluid essential for chip control

Recommended Speeds: 60-80 SFPM for HSS tools, 150-200 SFPM for carbide

Tooling Notes: Use blade width appropriate for workpiece diameter

Stainless Steel

  • • Work hardening can cause binding
  • • Lower speeds required
  • • Heavy cutting fluid flow essential

Recommended Speeds: 40-60 SFPM for HSS tools, 100-150 SFPM for carbide

Tooling Notes: Sharp tools crucial, rigid holder mandatory

Aluminum

  • • Higher speeds possible
  • • Can gall on tool face
  • • Good chip evacuation needed

Recommended Speeds: 100-150 SFPM for HSS tools, 300-400 SFPM for carbide

Tooling Notes: Polished tool faces help prevent buildup

Quality Control Specifications

Cut-off Length

Method: Digital calipers or micrometer

Tolerance: ±0.005" typical

Frequency: Every part

Face Squareness

Method: Dial indicator check

Tolerance: 0.002" TIR typical

Frequency: Sample basis

Surface Finish

Method: Visual inspection

Tolerance: 125 microinch typical

Frequency: Every part

Burr Height

Method: Visual and feel inspection

Tolerance: 0.005" maximum

Frequency: Every part

Operation Difficulty

Intermediate

Safety Guidelines

  • • Ensure parting tool is exactly at center height
  • • Use appropriate speeds - usually slower than turning
  • • Keep parting tool perfectly square to the work
  • • Support long workpieces properly
  • • Be prepared for the part to fall when separated

Required Tooling

  • Parting Tool

    Narrow blade designed specifically for parting operations

  • Part Catcher

    Optional tool to catch parts as they're parted off

  • Cutting Fluid

    Appropriate cutting fluid for material being parted

  • Dial Indicator

    For ensuring tool is square to the workpiece

Troubleshooting Guide

Tool Breakage

Ensure tool is exactly at center height, reduce speed, maintain rigid setup

Poor Surface Finish

Check cutting fluid application, verify speed/feed rates, use sharp tool

Tool Deflection

Minimize tool overhang, use proper blade thickness, ensure rigid mounting

Uneven Cutting

Check chuck jaw condition, use steady rest for long parts, maintain alignment

Binding Near Center

Reduce feed rate near center, ensure proper relief angles, watch chip formation

Pro Tips & Tricks

Tool Height Setting

Set parting tool exactly at center height. Even slight misalignment causes binding.

Best for: All parting operations, critical for success

Speed Reduction

Reduce speed as tool approaches center. For larger diameters, start at 60% normal turning speed.

Best for: All parting operations over 1" diameter

Support Methods

Use follow rest or catchment system for long parts. Consider groove location relative to chuck.

Best for: Long workpieces and production runs

Final Break

Reduce feed rate for last 0.100". Be prepared for part separation with proper support.

Best for: All parting operations, critical for part quality