Technical reference
A labeled reference for the dimensions, angles, and cutting-edge features used to describe end mills — the terms you'll see on a spec sheet, in a catalog, or in a tool print.
Complete end mill terminology reference
What each labeled dimension and feature means.
Overall dimensions
The helical groove that forms the cutting edge and channels chips away from the cut.
The curved transition where the flute's helix meets the end of the tool.
A reduced-diameter section behind the cutting length, used for clearance in deep or tight features.
The cylindrical, non-cutting portion held by the tool holder or collet.
The cutting diameter — the diameter measured across the flutes at their widest point.
The diameter of the shank, sized to match a specific collet or holder.
The usable flute length available to engage the workpiece.
The total length of the tool, from tip to the end of the shank.
End view & clearance geometry
The narrow flat left behind the cutting edge before the relief begins.
The first relieved surface behind the edge, sized to reduce rubbing without weakening the edge.
The relief angles ground behind the cutting edge — primary closest to the edge, secondary further back — that keep the tool from rubbing the workpiece.
The angle of the cutting face relative to the tool's centerline, viewed from the end — it controls how aggressively the edge shears material.
Cutting edge & helix
Where the peripheral (outside diameter) cutting edge meets the end cutting edge — often the first point to wear.
The cutting edge running along the outside diameter, doing most of the side-milling work.
The cutting edge across the bottom face, which allows the tool to plunge and face-mill.
The relief cut into the end face that creates clearance for the end cutting edge and lets chips evacuate during plunging.
A slight dish ground into the end face so the center cuts cleanly and the tool can plunge without rubbing.
The rake angle of the end cutting edge, measured along the tool's axis.
The angle of the flute relative to the tool's axis — higher helix angles generally cut smoother and evacuate chips more efficiently.
The relief angles behind the end cutting edge, primary and secondary, that keep the tool face from rubbing when plunging or facing.
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