Cut-Off Blades

Cut-Off Blades

Cut-off (parting) blades are used in lathe work to separate a finished workpiece from the bar stock, cut grooves, and face the end of a workpiece. Parting is a technically demanding operation — the blade is narrow, the depth of cut is greater than the blade width, and chip evacuation is restricted by the close-fitting slot walls. Getting tool geometry, feed rate, and cutting speed right is essential to avoid the chatter, blade deflection, and blade breakage that characterises poorly executed parting operations. AIMS Industrial supplies cut-off blades and parting tools for manual and CNC lathes.

Blade Types and Materials

• HSS cut-off blades: High speed steel blades ground to standard widths (typically 2mm, 3mm, and 4mm). The economical choice for manual lathe work on mild steel, aluminium, brass, and similar materials. HSS can be re-ground when worn. T-style blades (wider at the back than the cutting edge) provide better support in the tool holder and reduce blade deflection in deep parting operations.
• Carbide-tipped blades: A brazed carbide tip on an HSS or alloy steel body combines the edge retention of carbide with a more economical substrate. Better suited to harder steels and higher production rates than HSS. When the tip wears, the body is not recoverable — carbide-tipped blades are replaced, not re-tipped in a production environment.
• Indexable insert parting systems: A holder accepts replaceable carbide insert tips. When an edge dulls, the insert is indexed to the next cutting edge or replaced. Preferred on CNC lathes and production manual lathes where tool change speed and consistent geometry are important.

Blade Width Selection

Cut-off blade width should be the minimum practical for the workpiece material and bar diameter — narrower blades use less material, generate less heat, and require less torque. However, very narrow blades in large diameter workpieces are more prone to deflection and chatter. Standard widths of 2–3mm suit most manual lathe work up to 50mm diameter; wider blades (3–4mm) are more stable for larger diameters.

Reducing Chatter and Breakage

Chatter in parting operations is usually caused by a combination of excessive blade overhang, insufficient feed rate, and incorrect cutting speed. Set the blade as close to the holder as the job allows, run the lathe at a slightly lower speed than roughing operations, and use a consistent feed rather than a hesitant one. Using cutting fluid during parting significantly reduces heat build-up in the blade and workpiece, improves surface finish, and extends blade life. Soluble oil or neat cutting oil applied continuously at the cutting zone is the correct approach; dry parting on steel accelerates wear and promotes the work-hardening that leads to chatter. For blade recommendations for specific materials and lathe sizes, contact our team.