Hair-line cracks are hardly visible and may arise due to the following reasons:
Improper regrinding by customer. E.g. Friction Martensite - The technical reason is a layer of surface martensite created by excessive friction from the grinder with the immediate result of small and big cracks.
This can be avoided with correct and careful grinding. Customer must check for suitable grinding abrasives and/or cooling during regrinding process. TKM can assist and give recommendations.
