Cutting-tool wear and tool breakage can create real production headaches. David Magnall, business development manager (products) at Seco Tools (UK) Ltd
(www.secotools.com), explains how machinists can tell when it is time to change tools.
“Different workpiece materials and different cutting conditions mean that a cutting edge is literally being attacked from all sides and has to cope with a great deal of hostility — changing mechanical loads, chemical attack and thermodynamic assault.
“Modern cutting materials — like Seco’s Duratomic coated carbide grades — combined with the correct tool geometries can withstand almost every cutting condition, but even the best will wear out over time. It used to be that cutting-tool wear was mainly confined to flank and crater wear and was easy to observe.
“Indeed, the wearing process could be followed, and the critical wear point could even be anticipated, enabling the operator to intervene, stop the cutting process and change the cutting edge. Today this is much more difficult to see or gauge. A cutting edge can look new and wear-free for a long time, then suddenly fail.
“Understanding tool wear and its causes will help manufacturers to modify their tool selection and machining strategies; there are also tell-tale signs that can help manufacturers to intervene at the optimum time. Specific signs can include a ‘grey zone’ appearing on the cutting edge; also a subtle chipping or crumbling of the cutting edge — or even a slight change in the shape and colour of the chips.
"Watching out for these signs — plus using a small tool-wear magnifying glass — will tell manufacturers when it is time to change the cutting edge.
“Through its STEP (Seco Technical Edu-cation Programme), Seco has developed an in-depth training module covering tool wear, based on cutting different workpiece materials. This tells manufacturers what to expect and what signs to look out for.”