Metal Lathe Tools : Cutoff / Parting Tools

  • Angles shown are good for hobbyists; grinds for production shops should consult a specialist.

  • Angles shown are the effective angles, not the ground angles. Effective angles are increased or decreased, based on the angle by which the tool is presented against the work. Additionally, the vertical alignment of the tool (vs. the center line of the work) can also change the effective Front Relief Angle.

  • All angles are given the nomenclature designated by the American Standards Association (ASA).
Carbide vs. HSS
Material Compressive Strength Shear Strength Max Usable Temp. *
Cemented Carbide Higher Lower 1,800 °F
HSS Lower Higher 950 - 1,100 °F

* Temperature at which the tool material begins to soften appreciably. For HSS, it depends on the level of cobalt in the HSS.

Tool Shape - Side View

Use Front Relief Angle Comments
Recom. Range
5° - 10° Angles shown are the recommended effective angles, not the ground angles. Greater relief angle will be needed when an upward-facing angle of presentation of the tool is used.

Tool Shape - Top View

Use Front Cutting Edge Angle Comments
Recom. Range
General 90° 70° - 110° 90° is recommended, but some like to skew the cutting edge. I've found that problematic on T-shaped cutters as they will tend to drift to one side.

Notes & Comments

Information regarding Grindstones

If grinding this on a high speed grinder, be sure to manage the temperature so that the temper is not lost due to overheating. If there is a carbide insert, DO NOT cool by dipping in water. This will cause the carbide to crack due to shocks. Otherwise, cool by dipping as needed in water.

For resharpening, a contour gauge like shown below is recommended. One should be made for each tool, and it should be numbered to match the tool's number.

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Remember : The goal of sharpening is to produce sharp tools, and these tools can injure you if mishandled. Safety measures should be followed to protect yourself and those in your shop. Be sure to read and follow all instructions from the manufacturer, and and utilize proper safety equipment. Never consume alcohol or anything that could impair your judgement before sharpening tools, or using sharp tools. Comments can be sent via eMail to me at