KEVOS® MAKEOS · Manufacturing
Grinding Wheel Cost Plan (Wear from G-Ratio, Dressing, Parts per Wheel, Cost per Part)
How much grinding wheel does each part use up through wear and dressing, how many parts will one wheel do, and what do the wheel and the grinding time cost per part?
Plan of grinding wheel use for an external cylindrical grinding job: the stock volume removed from each part, the wheel wear it causes from the grinding ratio (as the grinding geometry tool defines it), the wheel volume taken off by dressing shared over the parts between dressings, the usable wheel volume between the new and the discard diameter, the parts per wheel, the wheel cost and the grinding time cost per part from a specific removal rate, against a target cost per part.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Part | ||
| Work diameter before grinding | mm | Diameter of the part before grinding. |
| Ground length | mm | Length of the ground diameter. |
| Grinding stock on diameter | mm | Material removed on the diameter by grinding. |
| Wheel | ||
| Grinding ratio (metal removed ÷ wheel worn) | Grinding ratio for this wheel, work material and conditions: volume of metal removed per volume of wheel worn, measured or from the wheel maker. | |
| New wheel diameter | mm | Diameter of a new wheel. |
| Discard wheel diameter | mm | Smallest diameter at which the wheel is discarded (set by the flange size or the lowest safe speed). |
| Wheel width | mm | Width of the wheel. |
| Radial dressing depth per dressing | mm | Depth taken off the wheel radius at each dressing. |
| Parts ground between dressings | Number of parts ground between one dressing and the next. | |
| Wheel price | A$ | Price of a new wheel, on the same GST basis as the other costs. |
| Time and target | ||
| Specific removal rate per mm of wheel width | mm³/(mm·s) | Metal removal rate per millimetre of wheel width in contact, from your process or the wheel maker. |
| Spark-out and dwell time per part | s | Time per part for spark-out passes, dwell and the approach not covered by the removal rate. |
| Machine and operator rate | A$/h | Hourly cost of the machine and operator. |
| Target grinding cost per part | A$ | Grinding cost per part you aim for. |
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.
Part
What this means: Work diameter before grinding
- What it is
- The diameter of the part before grinding, used with the stock to find the volume of metal ground off.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 50 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger diameter means more metal removed for the same stock.
- Get it right
- Use the turned size before grinding, not the finished size.
What this means: Ground length
- What it is
- The length of the diameter being ground on each part.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 10000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 100 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Volume, wheel wear and time rise in proportion.
- Get it right
- For several ground diameters, add up their lengths if the stock and diameter are similar.
What this means: Grinding stock on diameter
- What it is
- The amount removed from the diameter by grinding, the grinding allowance left by the previous operation.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 20 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.3 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Volume removed, wheel wear and grinding time rise roughly in proportion.
- Get it right
- Keep it as small as the previous operation allows; every extra tenth adds wheel wear and time.
Wheel
What this means: Grinding ratio (metal removed ÷ wheel worn)
- What it is
- The grinding ratio: the volume of metal removed for each unit volume of wheel worn away, a measure of how well the wheel stands up on this job.
- Units and format
- Enter a plain number with no unit. The form accepts 0.01 to 100000. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A higher ratio cuts the wheel wear per part in proportion.
- Get it right
- Measure it over a run by gauging the wheel and the parts; it varies widely with wheel grade, work material and coolant.
What this means: New wheel diameter
- What it is
- The outside diameter of a new grinding wheel.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 3000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 400 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger new wheel gives more usable volume and more parts per wheel.
- Get it right
- Use the marked diameter of the wheels you buy.
What this means: Discard wheel diameter
- What it is
- The diameter at which a worn wheel is taken off and discarded, set by the flanges or by the lowest speed at which it still grinds well.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 3000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 300 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 discard diameter leaves more usable wheel.
- Get it right
- Use your shop’s discard size for this machine and wheel.
What this means: Wheel width
- What it is
- The width of the grinding wheel face, which sets the wheel volume and, with the specific removal rate, the removal rate.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 40 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A wider wheel has more volume and removes metal faster.
- Get it right
- Use the face width actually in contact with the work.
What this means: Radial dressing depth per dressing
- What it is
- The depth taken off the wheel’s radius each time it is dressed to restore its shape and sharpness.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 5 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.02 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Dressing wheel use rises in proportion.
- Get it right
- Dress no deeper than needed to clean up the face; the minimum that restores the wheel is the cheapest.
What this means: Parts ground between dressings
- What it is
- The number of parts ground between one dressing and the next.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 100000. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- More parts between dressings cut the dressing wear per part.
- Get it right
- Set it from the point at which size or finish starts to drift, not by habit.
What this means: Wheel price
- What it is
- The price of a new grinding wheel, spread over the parts it grinds.
- Units and format
- Enter a number in A$: A$. The form accepts 0 A$ to 10000000 A$. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 450 A$ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Wheel cost per part rises in proportion.
- Get it right
- Use the delivered price on the same GST basis as the other costs.
Time and target
What this means: Specific removal rate per mm of wheel width
- What it is
- The volume of metal removed per second for each millimetre of wheel width in contact, the specific removal rate of the process.
- Units and format
- Enter a number in mm³/(mm·s): mm³/(mm·s). The form accepts 0.000001 mm³/(mm·s) to 1000 mm³/(mm·s). Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 mm³/(mm·s) 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 shortens the grinding time per part.
- Get it right
- Take it from your own cycle times or the wheel maker’s recommendation for this material and finish.
What this means: Spark-out and dwell time per part
- What it is
- Time per part spent on spark-out passes, dwell and approach that remove little metal but are needed for size and finish.
- Units and format
- Enter a number in s: seconds. The form accepts 0 s to 3600 s. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 6 s as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Adds directly to the time per part.
- Get it right
- Measure it on the machine; it is often a large share of a short grinding cycle.
What this means: Machine and operator rate
- What it is
- The hourly cost of the grinding machine and its operator, applied to the grinding time.
- Units and format
- Enter a number in A$/h: A$/h. The form accepts 0 A$/h to 100000 A$/h. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 120 A$/h as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Time cost per part rises in proportion.
- Get it right
- Use your costing rate for the machine, including overheads if the target includes them.
What this means: Target grinding cost per part
- What it is
- The grinding cost per part you are aiming for, against which the wheel and time cost is compared.
- Units and format
- Enter a number in A$: A$. The form accepts 0 A$ to 1000000 A$. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.5 A$ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Only moves the pass line.
- Get it right
- Compare like with like: include only wheel and grinding time if that is what the target covers.
Method and formulas
- Stock volume per part V_w = π ÷ 4 (d_w² − (d_w − s)²) L; wheel wear per part = V_w ÷ G (G as defined by the grinding geometry tool).
- Dressing volume per part = π D_mean b a_d ÷ parts per dressing, with D_mean the mean of the new and discard diameters.
- Usable wheel volume = π ÷ 4 (D₀² − D_min²) b; parts per wheel = usable volume ÷ (wear + dressing) per part.
- Grinding time = V_w ÷ (Q′ b) + spark-out; cost per part = wheel price ÷ parts per wheel + time × rate.
- Example: each part uses 205.42 mm³ of wheel, 42.822 % of it in dressing; a wheel does 10,705 parts at A$0.042035 each, and the part costs A$1.2208 to grind.
Limitations
- The grinding ratio is taken as constant over the wheel's life; it changes with wheel diameter, speed, coolant and dressing.
- External cylindrical plunge or traverse grinding with the full wheel width in contact; wheel truing after mounting and breakage are not included.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Estimate grinding wheel cost per part
- See how much of the wheel goes in dressing rather than grinding
- Compare the effect of a better grinding ratio or less frequent dressing
Who it is for
- Grinding machinists
- Process planners
- Cost estimators
What you get
- Stock volume per part and wheel wear from the grinding ratio
- Dressing volume per part and share of the wheel lost to dressing
- Usable wheel volume, parts per wheel and wheel cost per part
- Grinding time and total grinding cost per part
Interpreting the result
- Dressing often takes as much wheel as grinding does: less frequent or lighter dressing can halve the wheel cost without changing the wheel.
- Wheel cost is usually a small part of grinding cost; the time per part dominates.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1196–1199, 1199–1268. 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.
Method explained here · Library collection
Grinding, honing and lapping: finishing hard parts to tight tolerances
What it covers: How abrasive processes work, how to read a grinding wheel specification, the main grinding methods, honing and lapping, avoiding grinding burn and the design details that make finishing easier.
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.