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