Dovetail cutters

An ideal groove with a 10.00 mm mouth, 3.00 mm wall height and 30° walls from vertical is 13.4641 mm wide at the bottom. A matching 12.00 mm head and 8.00 mm neck leave 0.2679 mm nominal neck clearance at the modeled side offset. The head needs open-end entry or another sufficiently large opening. Check the actual assembly and path.

Function and construction

A dovetail cutter has a head wider than its neck and mills sloped undercuts. Check permissible motion for the body and insert combination. Haas Tooling, Indexable Dovetail Cutters

Solid and indexable constructions have different interfaces. Harvey Tool's general dovetail family is solid carbide, with uncoated and AlTiN-coated offerings and both sharp and radiused corner options. Its table separates cutter diameter, cutting length, neck diameter, corner radius, flute count, shank diameter and overall length. Importantly, its diameter note measures over the radii rather than to a theoretical sharp corner. Harvey Tool, Dovetail Cutters.

Haas's retrieved indexable overview instead describes 60° bodies accepting D-style inserts and 45° bodies accepting V-style inserts. It distinguishes the inserts' 55° and 35° rhombic shapes from those body angles, and makes insert inscribed-circle size dependent on the body. Thus, an insert-shape angle is not the cutter's dovetail angle, and a broadly similar insert shape does not establish body compatibility. Haas, body and insert descriptions.

Geometry, entry and stiffness

The main dimensions answer different questions:

This table is explanatory synthesis. A drawing's wall angle, a catalog's included angle and an angle measured from the floor can use different references. The geometric example below defines its reference directly, without assigning a catalog angle designation.

Harvey's micro-dovetail discussion explains that flutes reduce the core below the nominal neck diameter. Its drop-hole comparison illustrates how an enlarged entry can allow a substantially thicker neck. A head that fits the finished undercut may still be too wide to pass through the slot mouth. An open slot end or a permitted entry hole changes the access problem; nominal finished width alone does not resolve it. Harvey Performance, “Dodging Dovetail Headaches,” April 27, 2017.

Cutting conditions are tied to the neck and engagement

Harvey's Dovetail Cutter Guide uses the larger cutter diameter for its surface-speed calculation but the smaller neck diameter to select chip load. This is a manufacturer-specific selection method, not a redefinition of feed per tooth. The guide uses descending radial passes at full axial depth and derives geometric maximum radial stock from (head diameter − neck diameter)/2. Its tables depend on tool identity and material hardness, and its posted values are starting guidance. It also distinguishes cutting one side from simultaneous engagement of both sides. A geometric radial allowance is therefore not a recommended one-pass cut. Harvey Tool, Dovetail Cutter Guide, pp. 1–2.

The micro-dovetail article links increasing engagement with the need for diminishing stepovers. It also describes chip packing in the partly enclosed groove and warns that excessive coolant force can deflect or break a microtool. Its account supports treating chip removal and tool loading together, rather than assuming more coolant pressure always improves the result. Harvey Performance, micro-dovetail application discussion.

Worked example: undercut width and entry

Use the hypothetical symmetric groove with straight walls leaning 30° from vertical. Exclude radii, tolerances, runout and deflection.

Undercut per side = wall height × tan(wall angle from vertical)
                 = 3.00 × tan(30°) = 1.7321 mm
Bottom width = mouth width + 2 × undercut per side
             = 10.00 + 2 × 1.7321 = 13.4641 mm

Now assume an ideal cutter with matching wall slope, a 12.00 mm maximum head diameter, an 8.00 mm neck, and sufficient cutting and neck lengths. At a plane 3.00 mm above its widest lower edge, its ideal conical head diameter is:

Upper profile diameter = 12.00 − 2 × 3.00 × tan(30°)
                       = 8.5359 mm
Head-to-neck radial difference = (12.00 − 8.00)/2 = 2.00 mm

That 2.00 mm radial difference exceeds the groove's 1.7321 mm undercut, but is only a geometric comparison. To reach either bottom wall, the ideal cutter center offsets by (13.4641 − 12.00)/2 = 0.7321 mm from the groove center. At that offset, the neck reaches 4.00 + 0.7321 = 4.7321 mm from the centerline, leaving about 0.2679 mm to the mouth edge on that side. Actual relief, tolerances and neighboring surfaces are excluded.

Check entry independently. The 12.00 mm head needs an open end or a permitted opening wider than the 10.00 mm mouth.

Coverage and source limits

A geometrically matching dovetail does not establish fit, load capacity or clamping retention. Finished flank angle, position, radii and surface condition remain distinct from nominal tool dimensions. O-ring gland performance additionally depends on the seal and gland design; this article does not establish a sealing specification.

The Harvey article displays April 27, 2017. The live product pages and two-page cutter guide reviewed on November 2, 2026 PST have no separately verified issue dates. Their tool-specific recommendations are not adopted as universal speeds, feeds, depths or life guarantees. The ideal example excludes dynamic stability and complete toolholder/workpiece collision analysis.

Related reference

Cutting tools and tooling references