KEVOS® MAKEOS · Manufacturing
Slot Milling against High-Speed End Milling (Feed Rate, Equivalent Tooling Time, Cost per Part)
Does full slot end milling or high-speed end milling with a light radial cut cost less per part for my cut length, cutter, feeds, speeds and tooling costs, and by how much?
Comparison of two end milling strategies by the handbook’s machining econometrics: spindle speed from cutting speed and cutter diameter, feed rate from teeth, feed per tooth and speed, cutting time for the cut length and passes, equivalent tooling-cost time from the edge replacement time and the cost of the edges at the hourly rate, and the total cost per part of cutting, tool changing and tooling for full slot milling and for high-speed milling, with the cost ratio, the saving per part and per batch, and a check of both spindle speeds against the machine.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Job | ||
| Cutter diameter | mm | Diameter of the end mill, the same for both strategies as in the handbook comparison. |
| Cut length per pass | mm | Length cut in one pass along the feed direction; the handbook example uses 1000 mm. |
| Hourly rate of machine and operator (ex GST) | A$/h | Cost of the machine and operator per hour, excluding GST, from your machine-hour rate. |
| Parts in the batch | Number of parts in the batch, for the saving per batch. | |
| Maximum spindle speed of the machine | rpm | Highest spindle speed the machine can run, from its specification. |
| Full slot milling | ||
| Teeth (slot) | Number of teeth on the cutter for slotting. | |
| Feed per tooth (slot) | mm | Feed per tooth for full slotting at the tool life you enter, from your tooling data. |
| Cutting speed (slot) | m/min | Cutting speed for full slotting at that tool life, from your tooling data. |
| Tool life (slot) | min | Tool life in minutes at the slotting speed and feed. |
| Passes per part (slot) | Number of passes along the cut length to finish the part by slotting. | |
| Time to replace the edges (slot) | min | Time to replace the set of edges or the cutter for regrinding, in minutes. |
| Cost of the edges or cutter regrind (slot, ex GST) | A$ | Cost of the set of edges, or of a regrind, excluding GST. |
| High-speed milling | ||
| Teeth (high-speed) | Number of teeth on the cutter for high-speed milling. | |
| Feed per tooth (high-speed) | mm | Feed per tooth at the light radial cut (chip thinning allows a much higher feed), from your tooling data. |
| Cutting speed (high-speed) | m/min | Cutting speed at the light radial cut and the tool life you enter. |
| Tool life (high-speed) | min | Tool life in minutes at the high-speed conditions. |
| Passes per part (high-speed) | Number of passes needed to finish the same part with the light radial cut; a full-width feature normally needs several. | |
| Time to replace the edges (high-speed) | min | Time to replace the edges or the cutter for high-speed milling. |
| Cost of the edges or cutter regrind (high-speed, ex GST) | A$ | Cost of the edges or regrind for high-speed milling, excluding GST. |
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.
Job
What this means: Cutter diameter
- What it is
- Diameter of the end mill used for both strategies.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.5 mm to 200 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 25 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Sets the spindle speed for a given cutting speed.
- Get it right
- Use the actual cutter diameter.
What this means: Cut length per pass
- What it is
- Length cut in one pass along the feed direction.
- Units and format
- Enter a number in mm: millimetres. The form accepts 1 mm to 1000000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1000 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Cutting time and cost grow in direct proportion.
- Get it right
- Measure the toolpath length of one pass on the feature.
What this means: Hourly rate of machine and operator (ex GST)
- What it is
- Hourly cost of the machine and operator, excluding GST.
- Units and format
- Enter a number in A$/h: A$/h. The form accepts 1 A$/h to 10000 A$/h. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 50 A$/h as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Scales cutting cost and turns edge cost into equivalent time.
- Get it right
- Use your machine-hour rate with labour and overheads.
What this means: Parts in the batch
- What it is
- Number of parts made in the batch or order.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 10000000. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 100 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Only scales the saving per batch.
- Get it right
- Use the order or batch quantity.
What this means: Maximum spindle speed of the machine
- What it is
- Highest spindle speed the machine can run.
- Units and format
- Enter a number in rpm: revolutions per minute. The form accepts 100 rpm to 200000 rpm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20000 rpm 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 spindle speed checks.
- Get it right
- Take it from the machine specification, not the controller override.
Full slot milling
What this means: Teeth (slot)
- What it is
- Teeth on the cutter for full slotting.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 40. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 6 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- More teeth raise the feed rate in direct proportion.
- Get it right
- Fewer teeth leave room for chips in a full slot.
What this means: Feed per tooth (slot)
- What it is
- Feed per tooth for full slotting.
- 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 0.17 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Raises the feed rate and lowers the cost per part.
- Get it right
- Take it from your tooling data at the tool life you enter.
What this means: Cutting speed (slot)
- What it is
- Cutting speed for full slotting.
- Units and format
- Enter a number in m/min: metres per minute. The form accepts 0.000001 m/min to 5000 m/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 249 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Raises spindle speed and feed rate.
- Get it right
- Take it from your tooling data for the same tool life.
What this means: Tool life (slot)
- What it is
- Tool life at the slotting speed and feed.
- Units and format
- Enter a number in min: minutes. The form accepts 0.1 min to 10000 min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 45 min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Longer life lowers the tooling share of the cost.
- Get it right
- Use the life your tooling data give at these conditions.
What this means: Passes per part (slot)
- What it is
- Passes per part when slotting.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 1000. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Cost grows in direct proportion.
- Get it right
- Count the passes needed to finish the feature by slotting.
What this means: Time to replace the edges (slot)
- What it is
- Time to replace the set of edges or the cutter for slotting.
- Units and format
- Enter a number in min: minutes. The form accepts 0 min to 1000 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
- Adds to the equivalent tooling-cost time.
- Get it right
- Time a tool change including any presetting at the machine.
What this means: Cost of the edges or cutter regrind (slot, ex G…
- What it is
- Cost of the set of edges or a regrind for slotting, excluding GST.
- Units and format
- Enter a number in A$: A$. The form accepts 0 A$ to 100000 A$. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 A$ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Adds 60 × cost ÷ hourly rate minutes to the tooling time.
- Get it right
- Use the price per change divided by the uses you get.
High-speed milling
What this means: Teeth (high-speed)
- What it is
- Teeth on the cutter for high-speed milling.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 40. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 6 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- More teeth raise the feed rate in direct proportion.
- Get it right
- Light radial cuts allow more teeth.
What this means: Feed per tooth (high-speed)
- What it is
- Feed per tooth at the light radial cut.
- 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 0.628 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Raises the feed rate and lowers the cost per part.
- Get it right
- Take it from your tooling data; chip thinning allows a much higher feed than slotting.
What this means: Cutting speed (high-speed)
- What it is
- Cutting speed at the light radial cut.
- Units and format
- Enter a number in m/min: metres per minute. The form accepts 0.000001 m/min to 5000 m/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 375 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Raises spindle speed and feed rate.
- Get it right
- Take it from your tooling data for the same tool life.
What this means: Tool life (high-speed)
- What it is
- Tool life at the high-speed conditions.
- Units and format
- Enter a number in min: minutes. The form accepts 0.1 min to 10000 min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 45 min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Longer life lowers the tooling share of the cost.
- Get it right
- Use the life your tooling data give at these conditions.
What this means: Passes per part (high-speed)
- What it is
- Passes per part with the light radial cut.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 1000. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Cost grows in direct proportion.
- Get it right
- A full-width feature normally needs several passes; count them from the toolpath.
What this means: Time to replace the edges (high-speed)
- What it is
- Time to replace the edges or the cutter for high-speed milling.
- Units and format
- Enter a number in min: minutes. The form accepts 0 min to 1000 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
- Adds to the equivalent tooling-cost time.
- Get it right
- Time a tool change including any presetting.
What this means: Cost of the edges or cutter regrind (high-speed…
- What it is
- Cost of the edges or a regrind for high-speed milling, excluding GST.
- Units and format
- Enter a number in A$: A$. The form accepts 0 A$ to 100000 A$. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 A$ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Adds 60 × cost ÷ hourly rate minutes to the tooling time.
- Get it right
- Use the price per change divided by the uses you get.
Method and formulas
- Spindle speed rpm = 1000 V ÷ (π D); feed rate FR = z f_z rpm (mm/min).
- Cutting time per part = passes × Dist ÷ FR (minutes).
- Equivalent tooling-cost time T_V = T_RPL + 60 C_E ÷ HR (minutes).
- Total cost per part c_tot = HR × (passes × Dist ÷ FR) × (1 + T_V ÷ T) ÷ 60.
- Saving per part = c_tot(slot) − c_tot(high-speed); per batch = saving × parts; ratio = c_tot(high-speed) ÷ c_tot(slot).
- Example: slotting at 3,233.8 mm/min costs A$0.33787 per part and high-speed milling at 17,991 mm/min costs A$0.06073, 17.975 % of the slotting cost.
Limitations
- Costs of idle and slack time are not included, as in the handbook comparison; add handling and set-up with the milling cost tool.
- The feed per tooth, cutting speed and tool life for each strategy must come from your tooling data at the same tool life basis; the handbook values are for its example steel and cutters.
- Results hold for perfect milling conditions (no run-out, accurate sharpening), as the handbook notes.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Decide between slotting and a light radial-cut strategy for a feature
- Show the cost effect of more teeth or a higher feed per tooth
- Put a figure on the saving per batch for a process change
Who it is for
- Process and production engineers
- CNC programmers
- Estimators
What you get
- Spindle speed and feed rate for each strategy
- Cutting time per part
- Equivalent tooling-cost time
- Total cost per part for each strategy
- Cost ratio, saving per part and saving per batch
- Spindle speeds against the machine
Interpreting the result
- A light radial cut lets the feed per tooth rise sharply for the same chip thickness, so the feed rate and cost per part improve even when more passes are needed.
- More teeth raise the feed rate in both strategies but also the tooling cost per change; compare with the right edge cost.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1167–1169. 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 · Library collection
Milling cutters and milling strategies: speeds, feeds, chip thickness and parts that are easy to mill
What it covers: How milling works, the main cutter types, climb versus conventional milling, calculating speed and feed, chip thinning, adaptive toolpaths, chatter and design rules that make milled parts cheaper.
Useful alongside · KEVOS® original book
Milling: feed per tooth, chip thinning and feed rate
What it covers: Calculate milling feed rates from feed per tooth, correct for radial chip thinning and lead angle, and estimate removal rate and time for side milling and face milling.
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.