BIZOMAT MAKEOS · Manufacturing
Taylor Tool Life and Economic Cutting Speed
How long will the tool last at this speed, and what speed gives the lowest cost per part?
Tool life from the Taylor equation (from constants or two test points), and the minimum-cost and maximum-production cutting speeds and tool lives from machine rate, tool cost and tool change time.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Taylor constants | choice | Enter known Taylor constants, or fit them from two tool-life tests in the same conditions. |
| Taylor exponent n | Taylor exponent for the tool and work material (often about 0.1–0.17 for HSS, 0.2–0.5 for carbide). | |
| Taylor constant C (speed for 1 min life) | m/min | Cutting speed giving one minute of tool life. |
| Two tool-life tests | ||
| Test 1 cutting speed | m/min | Speed of the first tool-life test. |
| Test 1 tool life | min | Measured tool life (minutes of cutting to the wear limit) in test 1. |
| Test 2 cutting speed | m/min | Speed of the second test (different from the first). |
| Test 2 tool life | min | Measured tool life in test 2. |
| Planned speed and costs | ||
| Planned cutting speed | m/min | Speed you plan to run. |
| Machine and operator rate | AUD/h | Cost of machine and operator per hour. |
| Tool cost per cutting edge | AUD | Insert cost divided by usable edges, or regrind cost per edge. |
| Tool change time | min | Time to change or index the tool. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Taylor constants
- What it is
- Whether you already know the Taylor exponent and constant for this tool and material, or want the tool to fit them from two measured tool-life tests.
- Units and format
- Choose one of 2 options from the list: Enter n and C; Fit from two tool-life tests.
- Example
- The form opens with “Fit from two tool-life tests” selected as a worked example. Choose the option that matches your case.
- Get it right
- With two tests the n and C fields are ignored; with known constants the test fields are ignored.
What this means: Taylor exponent n
- What it is
- The exponent in Taylor’s equation that shows how sharply tool life falls as cutting speed rises. It is set by the tool and work material pair and comes from tool-life tests or published data.
- Units and format
- Enter a plain number with no unit. The form accepts 0.01 to 1. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.25 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Used only in the known-constants mode. Small changes in n move the economic speeds a lot.
What this means: Taylor constant C (speed for 1 min life)
- What it is
- The cutting speed that would give exactly one minute of tool life in Taylor’s equation, for the same tool, material and conditions as n.
- Units and format
- Enter a number in m/min: metres per minute. The form accepts 0.000001 m/min to 100000 m/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 400 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A higher C raises tool life at any speed and raises both economic speeds.
- Get it right
- Used only in the known-constants mode. Use n and C from the same data source; mixing them gives nonsense.
Two tool-life tests
What this means: Test 1 cutting speed
- What it is
- The cutting speed used in the first tool-life test, run until the edge reached your chosen wear limit.
- Units and format
- Enter a number in m/min: metres per minute. The form accepts 0.000001 m/min to 100000 m/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 200 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Run both tests with the same feed, depth, coolant and wear criterion; only speed should change.
What this means: Test 1 tool life
- What it is
- The cutting time in the first test until the edge reached the wear limit, counting only time in the cut.
- Units and format
- Enter a number in min: minutes. The form accepts 0.000001 min to 1000000 min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 40 min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Count only time actually cutting, not total cycle time with rapids and loading.
What this means: Test 2 cutting speed
- What it is
- The cutting speed used in the second tool-life test, different from the first, with all other conditions unchanged.
- Units and format
- Enter a number in m/min: metres per minute. The form accepts 0.000001 m/min to 100000 m/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 280 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Choose speeds far enough apart to give clearly different lives; close speeds make the fitted exponent unreliable.
What this means: Test 2 tool life
- What it is
- The cutting time in the second test until the edge reached the same wear limit as in test 1.
- Units and format
- Enter a number in min: minutes. The form accepts 0.000001 min to 1000000 min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- The higher of the two speeds must give the shorter life, or the fit is rejected.
Planned speed and costs
What this means: Planned cutting speed
- What it is
- The cutting speed you intend to run in production, for which the tool life is predicted and compared with the economic range.
- Units and format
- Enter a number in m/min: metres per minute. The form accepts 0.000001 m/min to 100000 m/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 260 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A higher speed shortens predicted tool life steeply.
- Get it right
- Keep it near the tested speeds; the Taylor model is unreliable far outside them.
What this means: Machine and operator rate
- What it is
- The cost of running the machine with its operator for one hour, including overheads, from your costing or finance team.
- Units and format
- Enter a number in AUD/h: Australian dollars per hour. The form accepts 0 AUD/h to 100000 AUD/h. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 120 AUD/h as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A higher rate raises the minimum-cost speed and shortens the minimum-cost tool life.
- Get it right
- Use the full machine and labour rate, not just the wage.
What this means: Tool cost per cutting edge
- What it is
- The cost of one usable cutting edge: the insert price divided by its usable edges, or the regrind cost per edge for solid tools.
- Units and format
- Enter a number in AUD: Australian dollars. The form accepts 0 AUD to 100000 AUD. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 8 AUD as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A dearer edge lowers the minimum-cost speed and lengthens the minimum-cost tool life.
- Get it right
- Divide the insert price by the number of edges you really use, not the number it has.
What this means: Tool change time
- What it is
- The time the machine stands idle while a worn edge is indexed or a tool is changed and the offset checked.
- Units and format
- Enter a number in min: minutes. The form accepts 0 min to 10000 min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A longer change time lowers both economic speeds and lengthens their tool lives.
- Get it right
- Include offset setting and first-part checking, not just turning the insert.
Method and formulas
- V T^n = C. From two tests: n = ln(V₁ ÷ V₂) ÷ ln(T₂ ÷ T₁); C = V₁ T₁^n.
- Tool life at speed V: T = (C ÷ V)^(1/n).
- Minimum cost: T_c = (1/n − 1)(t_c + C_t ÷ C_o), with C_o the cost rate per minute; V_c = C ÷ T_c^n.
- Maximum production: T_p = (1/n − 1) t_c.
- Example: the two tests give n = 0.24271, C = 489.63 m/min; the minimum-cost speed is 240.47 m/min with 18.721 min tool life.
Limitations
- The Taylor equation holds only over the range of the tests and for constant feed, depth and material.
- Non-cutting time and part handling do not affect the optimum speed but do affect total cost.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Choose a cutting speed that minimises cost
- Predict tool changes per shift
- Fit Taylor constants from two tool-life tests
Who it is for
- Manufacturing engineers
- Production planners
- Machinists
What you get
- Taylor constants n and C
- Tool life at the planned speed
- Minimum-cost tool life and speed
- Maximum-production tool life and speed
Interpreting the result
- Run between the minimum-cost and maximum-production speeds; never above the maximum-production speed.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1102–1124, 1132–1140. Topic reference; no source tables or recommended settings are reproduced.
Learn the Concepts Behind This Tool
These BIZOMAT Library readings explain the method this tool uses, with worked examples.
Method explained here · BIZOMAT original book
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