Corner Radius End Mills

Corner Radius End Mills

Corner radius end mills (bull nose end mills) are end mills with a small radius blended between the peripheral cutting edge and the flat bottom — rather than the sharp corner of a square end mill. This radius dramatically improves tool life by reducing chipping and edge breakdown at the most vulnerable point of the cutter. AIMS Industrial stocks corner radius end mills in HSS and solid carbide for milling machine and CNC machining centre use.

Why Corner Radius Matters

The sharp corner of a standard square end mill is the weakest point of the cutter — subject to the highest contact stress on every tool engagement. In hardened steels, stainless and titanium alloys, sharp corners chip or break progressively under the thermal and mechanical stress of milling, dramatically reducing tool life and surface quality. A corner radius distributes this stress over a larger area, maintains a stronger cutting edge geometry, and reduces the tendency for built-up edge and chipping. In hardened steel (45 HRC and above), corner radius end mills are often the only practical option for reliable peripheral milling.

Radius Options

Corner radius end mills are specified by nominal diameter and corner radius — common combinations include 10mm x R0.5, 12mm x R1.0, 16mm x R2.0 and 20mm x R2.0. The corner radius should match the required floor-to-wall radius in the milled pocket or profile; if not specified, a small radius (0.5mm to 1.0mm) provides most of the tool life benefit with minimal effect on slot geometry.

Applications

Peripheral slot milling in hardened and difficult-to-machine steels, contour milling with radiused corners, semi-finish and finish milling of complex 3D profiles in dies, moulds and aerospace components. For guidance on the right corner radius end mill for your material and application, contact our team. AIMS Industrial has been supporting Australian workshops since 1988.