Tool Wear: Notch Wear
This article is part of a 9-part series on tool wear and how to manage it. For insights into other wear mechanisms and how to address them, be sure to read the rest of the series.
Tool wear is arguably the most disruptive event—and a major cause of missed production time—on the manufacturing floor. It is also a key factor driving overall tooling spend. On most machines, production comes to a complete stop during tool changes. Additional time is lost when test cuts and offsets are made to reset the dimensional position of the cutting edge. Add inspection time and scrapped components due to wear or tool breakage—and all of this is before even addressing the time spent solving tool wear issues.
Of course, cutting tools don’t last forever, and while we can never fully eliminate the costs associated with tool wear, its disruptive effects can be reduced through an improved understanding of the various wear mechanisms—and by taking appropriate corrective actions.
Notch Wear
What it is:
Notch wear refers to a distinct “notch” or slice-like deterioration that forms at the cutting edge, specifically at the depth-of-cut line.
Why it happens:
Notch wear occurs when the surface or “skin” of the workpiece material is harder than the underlying base material. It is most commonly seen when rough machining work-hardening materials such as stainless steels and high-temperature alloys. It can also arise during the initial roughing passes on forgings and certain castings.
How to Correct:
Notch wear is difficult to eliminate entirely but can be effectively managed.
One straightforward approach is to vary the depth of cut during multiple-pass rough machining. For example, instead of making four identical passes of 0.125" per side to remove 1.0" of total diameter, try alternating with passes of 0.120", 0.150", 0.095", and 0.135". This variation distributes the notch-inducing forces across different parts of the cutting edge, delaying the development of a concentrated wear notch.
Other correction strategies include:
- Use a tool / insert combination with a larger lead angle. For example, use a square insert with a 15° lead angle instead of an 80° diamond insert with a -5° lead angle.
- Switch to a stronger insert geometry with a more reinforced edge line to improve resistance to notching.
- Reduce the feed rate to lower cutting stress on the insert and slow down the onset of notch wear.