How much extra length do I need on a spindle blank?

Add at least 25mm to each end (50mm total) for the drive centre and live centre to grip. If you are turning a piece that needs a tenon or specific detail at the very end, add more accordingly. The extra length is cut off after turning.

What size square blank do I need for a round spindle?

The blank should be square with each side at least 10% larger than the finished diameter. This accounts for the corners of the square being rounded off first. For a 40mm finished spindle, start with a 45mm square blank.

What speed should I use for spindle turning?

Start at lower speeds while the blank is still square (corners spinning). For initial roughing, stay below the calculated max RPM. Once the blank is round, you can increase speed for finer cuts. Thin spindles can run at high speeds; heavy or long ones should run slower.

How do I prevent spindle whip on long blanks?

For spindles longer than about 10x the diameter, use a steady rest to prevent whip (vibration). Alternatively, rough the spindle to near finished size at the steady rest end first, then move the steady and finish the other end. Keep cuts light on long spindles.

WoodCalcs

Spindle Turning Calculator — Blank Dimensions

Calculate spindle blank dimensions and lathe centre heights for spindle turning.

Finished Length

Finished Diameter

How We Calculate This

This calculator determines the blank dimensions needed for spindle turning between centres.

Formulas

Blank length = Finished length + 50mm (25mm each end for centres)

Blank square = Finished diameter x 1.1 (rounded up to nearest 5mm)

Blank diagonal = Square x sqrt(2)

Max RPM = 8,000 / Diagonal in inches

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify measurements and material quantities before cutting or purchasing.