Turning Tool Rest Calculator — Optimal Position

For spindle and external bowl turning, set the rest top a few millimetres (about 5mm) below the lathe centreline so the cutting edge — which rides on top of the rest — sits on or just below the centreline. For internal bowl work the edge should sit at or only slightly above the centreline, so keep the rest top level with the centreline rather than raising it with the bowl depth. A scraper is set a few millimetres above centre. Never raise the rest by the full workpiece radius — that drives the wood down onto the edge and causes a violent catch.

As close as safely possible, typically 10-20mm from the workpiece surface. A closer rest gives more control and leverage. Always spin the workpiece by hand before starting the lathe to check clearance. Re-adjust the rest as you remove material.

Re-position the rest whenever it is more than about 20-25mm from the workpiece, or when you change from external to internal cutting. Always stop the lathe before adjusting. Check clearance by rotating the workpiece by hand after each adjustment.

Yes. A higher rest angles the tool tip more steeply into the work, which can cause catches. A lower rest creates a more scraping action. The ideal height puts the bevel of the tool tip tangent to the workpiece surface at the cutting point.