Turning Cost Per Part Calculator
Cycle time alone does not tell you what a turned part costs. This calculator adds machine time, tool change time, insert cost and setup into one cost per part, and shows how tool life changes it.
Your numbers
Burdened hourly rate including operator.
Rapids, tool indexing, load and unload.
Your results
A simple cost model. It excludes material, inspection, scrap, overhead beyond the machine rate and finishing.
Cost per part vs tool life
Sweeps Tool life per edge from 3 to 60, holding your other inputs fixed.
Compare estimated and actual part cost
Optional: ask how actual job costs from your ERP could validate this model.
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How to use the calculator
Enter your burdened machine rate, the cutting time and non-cutting time per part from the program or a trial run, and the tool life you expect per edge in minutes of cut. Add insert price, edges per insert, edge change time and setup details. The result shows machine cost, tooling cost, setup per part and the total, and the chart sweeps tool life to show where gains flatten.
The cost model
Edges used per part equal cutting time divided by tool life. Each edge costs the insert price divided by usable edges, and every change adds downtime at the machine rate. Setup is spread across the lot. Pushing speed up shortens cutting time but also shortens tool life, so the lowest cost per part sits at a speed between the longest life and the shortest cycle, a result known from Gilbert's economic cutting speed analysis.
Reading the chart
At low tool life, change time and insert cost dominate and cost per part rises steeply. As life grows, the curve flattens because machine and setup cost take over. If your tool life sits on the steep part of the curve, a better grade, coolant fix or lower speed pays back quickly. If it sits on the flat part, further gains in life barely help and cycle time becomes the lever.
Common mistakes
Do not use catalog tool life for your own conditions; use the log. Do not forget that planned tool changes at fixed counts waste edge life. Avoid using a machine rate that excludes the operator when the operator is tied to the machine. Do not treat the result as a quote: add material, scrap, inspection and margin separately.
Frequently Asked Questions
What is a good tool life for turning?
There is no single value. Common practice aims for tool life in the range of roughly 10 to 30 minutes of cut for general turning, but the economic choice depends on insert cost, change time and machine rate. Use the chart to find your own.
Why does shorter tool life raise cost so quickly?
Each edge change takes the machine out of production and consumes an edge. When life is short, both effects occur more often per part, so cost per part climbs faster than linear at low life values.
Should I include material cost?
Not in this model. Add material, scrap allowance, inspection and finishing separately. The calculator focuses on the controllable machining and tooling cost so you can compare process options.
How do I find cutting time?
Use the cycle time from the CNC program simulation or time a good part and subtract load, unload and rapid motions. For quotes, cutting time can also be estimated from length divided by feed rate per pass times number of passes.
If your ERP holds routings and machine rates, Netray can help compare estimated cost per part to actual job costs.
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