How to improve tool life in turning

The three main machining parameters when turning are speed, feed, and depth of cut. Each has an effect on tool life, for best turning tool life:

  Reduce cutting speed, vc (to reduce heat)
  Optimize feed, fn (for shortest cutting time)
  Optimize depth of cut, ap (to reduce the number of cuts)

Cutting speed, vc Too low

  Built-up edge
  Dulling of edge
  Uneconomical
  Poor surface

Too high

  Rapid flank wear
  Poor finish
  Rapid crater wear
  Plastic deformation

Cutting speed, vc, has a large effect on tool life. Adjust vc for best economy vc. (Tool life on Y-axis)

Feed rate, fn Too light

  Stringers
  Rapid flank wear
  Built-up edge
  Uneconomical

Too heavy

  Less chip control
  Poor surface finish
  Crater wear/plastic deformation
  High power consumption
  Chip welding
  Chip hammering

Feed, fn, has less effect on tool life than vc. (Tool life on Y-axis)

Depth of cut, ap Too small

  Less chip control
  Vibration
  Excessive heat
  Uneconomical

Too deep

  High power consumption
  Insert breakage
  Increased cutting forces

Depth of cut, ap, has a small effect on tool life. (Tool life on Y-axis)

Tool maintenance

Establishing a routine for tool maintenance in the work shop will improve tool life in turning, prevent problems, and save money. Check the insert seat

It is important to ensure that the insert seat has not been damaged during machining or handling.

Look for:

  Oversized pockets due to wear. The insert does not seat properly in the pocket sides. Use a 0.02 mm (0.0008 inch) gauge ​to check the gap
  No gaps in the corners between the shim and the bottom of the pocket are allowed
  Damaged shims. Shims should not have chipped corners in the cutting area
  Wear on the shim from the chip breaking and/or impressions from the insert

Clean the insert seat

Make sure that the insert seat is free from dust or chips produced when machining. If necessary, clean the insert seat with compressed air. If boring bars with cutting heads are used, it is also important to check and clean the coupling between the head and the bar when changing the cutting head. Torque wrench

To get the best performance out of screw-clamp tool holders, a torque wrench should be used to correctly tighten the insert. Use the recommended torque for each tool holder.

  A too high torque will affect the performance of the tool negatively and cause insert and screw breakage
  A too low torque will cause insert movement, vibrations and degrade the cutting result

Clamping screws

Always use a torque wrench to ensure that screws are correctly tightened. Apply sufficient screw lubrication to prevent the screw from seizing. Lubricant should be applied to the screw threads as well as the screw head face. Replace worn or damaged screws.

TOOL LIFE PREDICTION OF TUNGSTEN CARBIDE CUTTING TOOLS IN TURNING PROCESS

Abstract. Cutting tools can be used when they do not reach tool life criteria and can produce parts with desired surface finish and dimensional accuracy. Flank wear of cutting tools is often selected as the tool life criterion because it determines the diametric accuracy of machining, its stability and reliability. Tool wear is defined as a gradual loss of tool material at contact zones of workpiece and tool material, resulting the cutting tool reaches its life limit. This article investigate the flank wear of tungsten-carbide plate (WC) during turning of C62D steel using design of experiments method. By using the multiple regression analysis between cutting speed, feed rate and depth of cut, it determines the effects of cutting conditions on Taylor tool life equation.

Study on carbide cutting tool life using various cutting speeds for α-β Ti-alloy machining