KEVOS® MAKEOS · Manufacturing
Grinding Economic Wheel Life and Wheel Speed
From the time to replace the wheel, the cost per dressing and the hourly rate, what is the equivalent tooling-cost time and the economic wheel life, and what wheel speed, removal rate and work speed follow from my Taylor constant at the economic life?
The handbook’s economic wheel life for grinding: equivalent tooling-cost time TV = TRPL + 60 × CE ÷ HR minutes with CE the cost per wheel dressing (the wheel cost per dressing plus the cost of dressing) and HR the hourly rate, economic life TE = 3 × TV, the wheel speed on the Taylor line V × T^0.26 = C at that life, the specific metal removal rate SMRR = 1000 × ECT × V and the work speed Vw = SMRR ÷ (1000 × ar).
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Time to replace or dress the wheel TRPL | min | Time to change or dress the wheel each time it is worn. |
| Wheel cost per dressing | $ | Share of the wheel price used up in each dressing. |
| Cost of one dressing | $ | Cost of carrying out one dressing, such as the dresser wear. |
| Hourly rate of machine and operator | $/h | Hourly rate of the machine and operator. |
| Taylor constant C at the chosen ECT (V × T^0.26) | m/min | Taylor constant for the work material group and ECT, from the grinding data tables or your calibration. |
| Equivalent chip thickness ECT | mm | Equivalent chip thickness of the grinding cut. |
| Radial depth of cut ar | mm | Radial depth of cut of the pass. |
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: Time to replace or dress the wheel TRPL
- What it is
- Time lost each time the wheel is changed or dressed.
- Units and format
- Enter a number in min: minutes. The form accepts 0.000001 min to 600 min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1 min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- TV rises minute for minute with it.
- Get it right
- Time it from stopping the cycle to grinding again.
What this means: Wheel cost per dressing
- What it is
- Part of the wheel price used up by each dressing.
- Units and format
- Enter a number in $: an amount of money; use one currency for every money input. The form accepts $0 to $100000. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with $3 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Adds to the cost per dressing CE.
- Get it right
- Divide the wheel price by the number of dressings it gives before it is discarded.
What this means: Cost of one dressing
- What it is
- Cost of the dressing operation itself, such as diamond wear.
- Units and format
- Enter a number in $: an amount of money; use one currency for every money input. The form accepts $0 to $100000. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with $2 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Adds to the cost per dressing CE.
- Get it right
- Include the dresser cost per dressing; the labour is covered by TRPL.
What this means: Hourly rate of machine and operator
- What it is
- Cost of an hour of the grinder and its operator.
- Units and format
- Enter a number in $/h: money per hour. The form accepts $0.000001/h to $10000/h. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with $120/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 lowers TV and so shortens the economic life.
- Get it right
- Use your shop rate for the machine, including overheads.
What this means: Taylor constant C at the chosen ECT (V × T^0.26)
- What it is
- Constant of the Taylor line V × T^0.26 for the work material group and ECT.
- 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 4690 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The wheel speed at the economic life rises in proportion.
- Get it right
- Take it from the grinding data tables or calibrate it from a shop result.
What this means: Equivalent chip thickness ECT
- What it is
- Average chip thickness along the cutting edge, the equivalent chip thickness.
- Units and format
- Enter a number in mm: millimetres. The form accepts 1e-7 mm to 0.1 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.00033 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The specific removal rate rises in proportion.
- Get it right
- Use the ECT the Taylor constant was read at.
What this means: Radial depth of cut ar
- What it is
- Depth the wheel cuts into the work on each pass.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 10 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.01 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A smaller depth needs a higher work speed for the same removal rate.
- Get it right
- Use the roughing or finishing infeed per pass.
Method and formulas
- CE = wheel cost per dressing + cost per dressing; TV = TRPL + 60 × CE ÷ HR (minutes).
- Economic wheel life TE = 3 × TV.
- Taylor line V × T^0.26 = C, so V at TE = C ÷ TE^0.26.
- SMRR = 1000 × ECT × V (mm³/mm/min); work speed Vw = SMRR ÷ (1000 × ar) (m/min).
- Example: TV is 3.5 min, so the economic wheel life is 10.5 min at 2,544.9 m/min.
Limitations
- The simple rule TE = 3 TV is the handbook’s recommendation for minimum cost; the global optimum also depends on the ECT.
- Check that the wheel speed is within the maximum operating speed marked on the wheel.
- C must be for the same work material group, wheel and ECT.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Set the wheel life for minimum grinding cost
- Find the wheel speed and work speed at the economic life
- See how dressing cost and rate change the economic life
Who it is for
- Manufacturing engineers
- Grinding machinists
- Process planners
What you get
- Equivalent tooling-cost time TV
- Economic wheel life TE
- Wheel speed at the economic life
- Specific removal rate and work speed
Interpreting the result
- In conventional grinders TV is usually 2 to 5 minutes, giving economic wheel lives of 6 to 15 minutes, as the handbook notes.
- Automatic dressing after each stroke makes TV small and the economic life short.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1200, 1205, 1215. Topic reference; no source tables or recommended settings are reproduced.
Learn the Concepts Behind This Tool
These KEVOS® Library readings explain the method this tool uses, with worked examples.
Useful alongside · KEVOS® original book
Machining economics: choosing a cutting speed
What it covers: Build a cost-per-part model from machine rate, cutting time, tool changes and tool cost, then find the minimum-cost and maximum-output speeds and see how flat the optimum is.
KEVOS® tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
Open the Grinding Economic Wheel Life and Wheel Speed calculator