How to Use a Parting Tool on a Wood Lathe: Sizing, Tenons and Parting Off

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To use a parting tool, rest it flat on its narrow edge on the tool rest with the handle low and the bevel touching the spinning wood, then slowly raise the handle so the edge starts to cut, and keep raising it as you feed straight in. The tool stays at 90 degrees to the work, the edge cuts at about center height, and the lathe slows down when you part all the way through. That one motion handles sizing cuts, tenons, grooves and parting off.

The parting tool is simple, but it is also where many beginners have their first catch or snap a thin blade. This guide covers what parting tools do, the types, a step-by-step for each common cut, sharpening and the mistakes to avoid.

What is a parting tool used for?

• Sizing cuts: cutting a groove to an exact diameter, checked with calipers, to set depths before shaping.
• Tenons: cutting a chuck tenon to fit the jaws, or a shoulder and pin to fit a hole.
• Grooves and beads: defining the edges of beads, and rolling small beads with a beading and parting tool.
• Parting off: separating finished work from waste.
• Square shoulders and clean ends on spindles.

Types of parting tools

Robert Sorby's line covers most of these: the 830H is a 1/8-inch standard parting tool, the 865H a 1/16-inch micro parting tool and the 833H a 3/8-inch beading and parting tool. Our guide to the best parting tool for a lathe compares them by width and bar shape.

Before you cut

1. Sharpen the tool with equal bevels (see below).
2. Set the tool rest close to the work and at about center height, and rotate the work by hand to check clearance. Our lathe tool rest height guide covers rest height for each tool.
3. Set a moderate speed for sizing cuts and a slower one for parting through. WEN's lathe manual says to adjust the lathe to a slower speed for parting through a workpiece.
4. Wear a face shield. Parting throws a fine stream of chips straight at you.

How to use a parting tool: step by step

1. The basic parting cut

1. Lay the parting tool on the rest on its narrow edge, perpendicular to the work.
2. Hold the handle low so the bevel touches the wood but nothing cuts.
3. Raise the handle slowly until the edge begins to cut. WEN's manual describes placing the tool on the rest, bringing the full bevel into contact, then gently raising the handle.
4. Keep raising the handle as you feed in, so the edge keeps cutting along an arc toward the center rather than scraping.
5. Keep the tool straight. Any twist binds it in the kerf.
6. For deep cuts, make a second cut beside the first to widen the kerf and give the tool clearance.

2. Sizing cuts with calipers

1. Set outside calipers to the target diameter plus a little for finishing.
2. Make a parting cut with one hand while holding the calipers in the groove with the other, lightly, on the side away from you.
3. Stop when the calipers slip over the bottom of the groove.
4. Repeat at each key diameter along the spindle, then shape between the grooves with a gouge.

Hold calipers only with a rounded, smooth tip and a light touch, and keep them square to the work; a caliper caught by the spinning wood can be pulled from your hand. A dedicated sizing tool that clamps to a parting tool, such as Robert Sorby's, makes repeat sizing cuts without a separate caliper.

3. Cutting a chuck tenon

1. Mark the tenon length from the end of the blank.
2. Set calipers or dividers to the tenon diameter your chuck jaws grip best.
3. Make a parting cut at the shoulder to the tenon diameter.
4. Remove the waste between the shoulder and the end with more parting cuts or a gouge.
5. Check the shoulder is square and the tenon is slightly dovetailed if your jaws are dovetailed.

Our how to use a lathe chuck guide covers tenon size and shape for different jaws.

4. Parting off

1. Slow the lathe.
2. Make the parting cut at the waste side of your final shape, leaving extra length if you plan to finish the end later.
3. Widen the kerf as you go deeper.
4. Between centers: stop short with a small core remaining, then switch off and finish the cut with a saw. Parting completely through with the tailstock engaged can trap the piece or tool.
5. In a chuck: part off toward the headstock side. WEN's manual says to hold the piece loosely in one hand as it separates from the waste; keep your hand behind the work, away from the cut, and only on small, light pieces.

5. Rolling a small bead with a beading and parting tool

1. Mark the bead's width with two shallow parting cuts.
2. Lay the tool bevel-down at the top center of the bead.
3. Roll it toward one groove while lifting the handle, then repeat to the other side.

How to sharpen a parting tool

Grind on the grinder's platform, one side then the other, so the two bevels meet in a centered point. Robert Sorby's ProEdge guide lists 20 degrees per side for its parting tools. Keep the bevels the same length; if one is longer, the tool steers in the cut. Hone lightly on a diamond plate. Our how to sharpen lathe tools guide covers the setup.

Why parting tools catch or break

WEN's troubleshooting table lists dull tools, a rest too low or too far from the work and the wrong tool for the job as causes of tools that grab or dig in. Those apply directly to parting tools.

Common mistakes

• Pushing straight in with the handle high. Start low and lift.
• Twisting the tool in a narrow groove.
• Parting through between centers with the tailstock tight.
• Using a parting tool on large bowl work where a bowl gouge or a wider tool is safer.
• Grabbing calipers too firmly in the groove.

FAQ

Next steps

Practice sizing cuts on a scrap spindle, then shape between them with a spindle gouge and finish with a skew. Our spindle turning and how to use a skew chisel guides take it from there.