Chamfer mills

An ideal 90° included cone with 2.00 mm flat tip reaches 8.00 mm local diameter at 3.00 mm above the tip plane. An 80 m/min target there gives 3,183 rpm. Using the 12 mm maximum profile instead gives 2,122 rpm, or 53.3 m/min at the 8 mm contact. Confirm the actual engaged edge and CAM reference.

Function and cutting geometry

A chamfer mill cuts sloping edges. Harvey describes beveling, deburring, countersinking and spotting where tip geometry and access permit. Harvey Performance, The Multiple Uses of a Chamfer Mill, 30 August 2017

Chamfer mills can have pointed or truncated conical profiles, different flute arrangements and different cutting diameters. A drawing's edge requirement and a cutter's catalog angle describe related geometry, but not necessarily with the same convention. The tool's substrate, coating, reach and workpiece-material application remain separate attributes.

Included angle versus angle per side

K-Tool explicitly labels its Multi-Purpose Chamfer Mill angles from the centerline, while its Long Edge Chamfer Mill angles are included angles. Its product list pairs 45° Multi-Purpose with 90° Long Edge tooling, and 30° with 60°. The same page references reverse-chamfer angles from the cutter's back face. These named conventions show why a bare angle number does not identify the same geometry across tool families. K-Tool, Complete Chamfer Product Line

For an ideal symmetric cone, an included angle of 90° means each side lies 45° from its axis. On mutually perpendicular horizontal and vertical faces, that geometry can form an equal-leg 45° chamfer when appropriately oriented. This is elementary geometry, not a statement that every 90° catalog tool produces the required feature without dimensional positioning or access constraints.

The chamfer's two projected legs and its sloping face width are also different dimensions. A 0.50 mm equal-leg chamfer has a face width of sqrt(0.50² + 0.50²) = 0.7071 mm. Treating the 0.50 mm leg dimension as the sloping width would describe a smaller feature.

Tip design changes the available operation

Harvey's tip-geometry guide distinguishes three of its offerings:

A flat end alone therefore does not establish end-cutting capability. The distance to theoretical sharp is a geometric reference for a truncated profile, not additional physical cutting length. These are Harvey's named categories, not a universal numbering system. Harvey Performance, Selecting the Right Chamfer Cutter Tip Geometry, 22 November 2019

Explanatory synthesis: an apparently suitable included angle does not resolve whether a tool can plunge, enter a narrow groove or blend into a floor. The actual tip, cutting-edge extent and surrounding tool envelope determine those possibilities. A non-cutting flat can occupy space without removing the material it touches.

Access and engagement

Sandvik distinguishes front and back chamfering. For back chamfers, the hole size limits cutter access; small internal features can favor solid-carbide tooling, while larger features allow indexable cutters. It also describes using other milling tools for chamfers on machines that can tilt the spindle or workpiece. “Chamfer milling” is therefore an operation, not just one fixed tool form. Sandvik Coromant, Chamfer milling

Its application guidance relates cutting data to the small depth and width of engagement and notes that surface-finish requirements constrain feed per tooth. Those observations do not provide a default feed or speed for an unidentified material and cutter. Its illustrated hole-chamfering sequence applies to the described tool and circular-interpolation arrangement, rather than all countersinking operations. Sandvik, application scope

Explanatory synthesis: access includes the hole entrance, cutting region, shank, holder and withdrawal path. A tool that reaches the front edge may not reach the reverse edge. Edge burrs, runout and tool deflection can also make the observed feature differ from the ideal cutter envelope.

Original example: cone reference and local diameter

Use an ideal 90° included cone from 2.00 mm tip to 12.00 mm maximum profile. Measure from the flat-tip plane and exclude relief, radii, runout and deflection.

For a symmetric cone with included angle α:

D(z) = d_tip + 2 × z × tan(α/2).

At z = 3.00 mm, the local diameter is 2.00 + 2 × 3.00 × tan(45°) = 8.00 mm. The ideal cone would reach 12.00 mm at z = 5.00 mm. These distances locate sections of the model; they do not give total spindle travel from an arbitrary work offset.

The missing theoretical point lies 1.00 mm below the physical tip, because (2.00/2)/tan(45°) = 1.00 mm. Confusing those reference origins introduces a 1.00 mm axial discrepancy in this invented model. The calculation does not establish the actual length-reference convention in a CAM system or supplier drawing.

Original example: cutting speed at the engaged region

Suppose contact is represented by the model's 8.00 mm diameter and a hypothetical cutting-speed target of 80 m/min. Sandvik gives the metric relationship n = 1000 × v / (π × D) and distinguishes effective diameter at the actual cutting depth. Sandvik Coromant, Milling formulas and definitions

Using that local diameter gives n = 80,000/(π × 8) ≈ 3,183 rpm. Using the 12 mm maximum profile diameter instead gives approximately 2,122 rpm. At 2,122 rpm, an 8 mm contact diameter has a surface speed of approximately 53.3 m/min, not 80 m/min.

A real contact can span several diameters. Verify the actual engaged region, chip load, cutting force, finish and tool life.

Source dates and boundaries

Reviewed 2026-11-02 PST. Harvey's displayed article dates are 30 August 2017 and 22 November 2019. No separate technical issue date was verified for the live K-Tool or Sandvik references. The original examples use ideal cone geometry and explicitly assumed values. No unsupported PDF edition, default machining recipe or guaranteed workpiece compatibility is assigned.

Related: Center drills, ball nose end mills, and Cutting tools and tooling references.