Lathe Cycle Time Estimator

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Estimate your lathe job

Get a rough runtime from your blank, finished OD and ID, threads and grooves. Add loading, insert changes and setup for a batch estimate.

Material examples assume carbide turning and are illustrative, not toolmaker recommendations. Change the speed and feeds to match your actual process. Selecting a material alone does not overwrite your settings.

1 · Raw blank and finished part

OD = full outside diameter. ID = hole diameter (0 for solid). Length runs along the spindle axis. Raw dimensions are before cutting; finished dimensions are after. Reference only; not to scale.

Raw OD Raw ID · 0 for solid Blank length Finished OD Finished ID · 0 for solid Finished / machined length

One straight cylindrical section. Blank length is per piece, not full bar length. All extra blank length is treated as facing stock. For stepped sections or parting, enter additional cutting minutes below.

2 · Turning and facing assumptions

Feed travels along the part. Roughing depth and finish allowance are radial (half the diameter change). Facing depth is along the axis. Reference only; not to scale.

Turning cutting speed Maximum spindle RPM Roughing feed / rev Finishing feed / rev Roughing depth · radial Finish allowance · radial Facing depth · axial Extra feed travel / pass

3 · Optional drilling and bore

Drill diameter is the hole size. Extra travel covers the drill point and breakthrough. Boring enlarges an existing hole to the finished ID. Reference only; not to scale.

A finished ID requires an existing raw hole or drilling. This simplified drill model uses a through-hole length. Enter tip/breakthrough allowance and any peck time yourself.

Drill / enlarge a hole

Drill diameter Drilling cutting speed Drilling feed / rev Tip / breakthrough allowance

4 · Optional threads and external grooves

Thread length runs along the axis; lead is travel per revolution. Groove width runs along the axis, while groove depth goes radially inward. Reference only; not to scale.

Use count 0 to exclude an operation. Thread passes include spring passes. Enter thread lead per revolution (equal to pitch for single-start threads). Groove depth is radial; the model uses adjacent plunges.

Thread featuresLength / thread Thread lead / revolution Thread spindle RPM Passes / threadExternal groove countGroove width Groove radial depth Grooving insert width Groove plunge feed / rev Thread / groove return

5 · Handling and machine idle time

Count loading, turret indexes, inspection and other idle seconds per part. Include rapid positioning per pass. These are separate from cutting time. Reference only; not to scale.

Load + unload / part Turret indexes / partSeconds / turret index Extra rapid / positioning per pass Inspection / part Other idle / part Other cutting / part Extra allowance

6 · Batch and one-time setup

Setup minutes are added once for the whole job. Quantity repeats the part cycle. Insert-change time is added at your chosen parts-between-changes interval. Reference only; not to scale.

Part quantitySetup · entire job Parts between insert changesMinutes / insert change

Setup is added once. Insert changes occur between parts: floor((quantity − 1) ÷ interval). First insert is assumed ready; setup and scheduled insert changes do not get the per-part allowance.

Enter your part and select Estimate runtime.

Formulas, assumptions and limits

RPM = 1,000 × cutting speed (m/min) ÷ (π × diameter in mm), capped at maximum RPM. Inch inputs are converted first. Cutting minutes = feed travel ÷ (feed per revolution × RPM).

Rough passes = ceil((radial stock − reserved finish stock) ÷ radial DOC). OD and bore use a fixed RPM calculated at the mean of starting and finished diameter. A single finish pass is added only when there is removal and a positive finish allowance. Facing uses raw-OD RPM and radial feed travel. This is not a simulation of constant surface speed.

Threads = features × passes × ((thread length + approach) ÷ (lead × capped RPM) + entered return time). Grooves = count × ceil(width ÷ insert width) × ((radial depth + approach) ÷ (feed × RPM) + return time). The generic per-pass positioning allowance is added separately to all modeled passes.

Per part = (cutting + pass positioning + turret indexes + handling/idle) × (1 + allowance % ÷ 100). Batch = setup + quantity × per-part time + scheduled insert-change time. This is a planning estimate, not a validated cycle time, confidence interval or machining program. No automatic allowance for peck cycles, acceleration, spindle ramps, work transfers, tool wear or chip problems unless you enter that time. Reconcile it against a proven job or CAM simulation.

Formula reference: Sandvik Coromant turning formulas. Material values, pass strategy and allowances here are editable examples, not manufacturer cutting recommendations.