BIZOMAT MAKEOS · Manufacturing
Number of Teeth for a Milling Cutter
How many teeth should this face mill or peripheral cutter have for the cut and the power available?
Recommended number of milling cutter teeth by the handbook formulas: for face mills from cutter diameter and width of cut, for peripheral cutters from diameter, depth of cut and helix angle (both for two teeth in the cut, scalable to another number), and for high-speed milling from the power available, feed per tooth, speed, depth and width of cut.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Rule | choice | Which handbook rule to apply. |
| Cutter diameter | mm | Cutter diameter. |
| Width of cut | mm | Width of cut (face milling and power rule). |
| Depth of cut | mm | Depth of cut (peripheral and power rule). |
| Helix angle (peripheral) | ° | Helix angle of a peripheral cutter. |
| Teeth wanted in the cut | Number of teeth to have cutting at once (the formulas assume two). | |
| Power available at the cutter | kW | Power available at the cutter. |
| Feed per tooth | mm | Feed per tooth. |
| Cutter speed | rpm | Cutter speed. |
| Work material (power rule) | choice | Work material constant: removal rate per kilowatt (handbook values 0.65, 1.5 and 2.5 in³/min per hp, converted). |
| Material constant K (entered) | mm³/min per kW | Your own removal rate per kilowatt for the material. |
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: Rule
- What it is
- Which handbook rule sets the tooth count: a face mill or a peripheral cutter sized for teeth in the cut, or a cutter sized by the power available for high-speed milling.
- Units and format
- Choose one of 3 options from the list: Face mill (teeth in cut); Peripheral cutter (teeth in cut); Power available (high-speed milling).
- Example
- The form opens with “Face mill (teeth in cut)” selected as a worked example. Choose the option that matches your case.
- Get it right
- Each rule uses different inputs; those the chosen rule does not use are ignored.
What this means: Cutter diameter
- What it is
- The diameter of the milling cutter measured across its cutting edges.
- 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 152.4 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- The face and peripheral rules use it; the power rule does not.
What this means: Width of cut
- What it is
- The width of work the cutter covers in one pass, measured across the direction of feed.
- 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 101.6 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Both the face mill and power rules give fewer teeth for a wider cut.
- Get it right
- Used by the face mill and power rules; for face milling it cannot exceed the cutter diameter.
What this means: Depth of cut
- What it is
- The depth of material the cutter removes, measured square to the machined surface.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 200 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 6.35 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A deeper cut gives fewer teeth in both the peripheral and power rules.
- Get it right
- Used by the peripheral and power rules only.
What this means: Helix angle (peripheral)
- What it is
- The helix angle of the teeth on a peripheral cutter, between the cutting edge and the cutter axis; straight teeth have 0°.
- Units and format
- Enter a number in °: degrees of angle. The form accepts 0° to 60°. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0° as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A higher helix angle gives fewer teeth, through the cos A term.
- Get it right
- Used by the peripheral rule only.
What this means: Teeth wanted in the cut
- What it is
- How many teeth you want cutting at the same time. The handbook rules are written for two and are scaled to your number.
- Units and format
- Enter a plain number with no unit. The form accepts 0.5 to 10. 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
- The face and peripheral results scale directly with this number.
- Get it right
- Not used by the power rule.
What this means: Power available at the cutter
- What it is
- The power the machine can deliver at the cutter for this cut, after losses in the spindle drive.
- Units and format
- Enter a number in kW: kilowatts. The form accepts 0.000001 kW to 1000 kW. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 7.5 kW as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- In the power rule the tooth count rises in proportion to the power.
- Get it right
- Power at the cutter, not the motor nameplate: multiply motor power by the drive efficiency.
What this means: Feed per tooth
- What it is
- The feed each tooth takes in one cutter revolution, also called the chip load.
- 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 0.2032 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 feed per tooth gives fewer teeth in the power rule.
- Get it right
- Per tooth, not per revolution or per minute: table feed ÷ (teeth × rpm).
What this means: Cutter speed
- What it is
- The rotational speed of the milling cutter during the cut.
- Units and format
- Enter a number in rpm: revolutions per minute. The form accepts 0.000001 rpm to 100000 rpm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 272 rpm 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 gives fewer teeth in the power rule.
- Get it right
- Used by the power rule only; convert cutting speed with n = 1000 V ÷ (π D).
What this means: Work material (power rule)
- What it is
- The work material group for the power rule, which sets the material constant K: the metal removal rate one kilowatt at the cutter can sustain.
- Units and format
- Choose one of 4 options from the list: Steel (K = 14,278); Cast iron (K = 32,950); Aluminium (K = 54,930); Enter K.
- Example
- The form opens with “Steel (K = 14,278)” selected as a worked example. Choose the option that matches your case.
- Get it right
- The built-in constants are handbook values converted from in³/min per hp; choose Enter K for other materials.
What this means: Material constant K (entered)
- What it is
- Your own metal removal rate per kilowatt at the cutter for the work material, from tooling data or your own cutting tests.
- Units and format
- Enter a number in mm³/min per kW: mm³/min per kW. The form accepts 0.000001 mm³/min per kW to 1000000 mm³/min per kW. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 14278 mm³/min per kW as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The tooth count in the power rule is directly proportional to K.
- Get it right
- Only used when the work material is set to Enter K.
Method and formulas
- Face mills: T = 6.3 D ÷ W (two teeth in the cut).
- Peripheral cutters: T = 12.6 D cos A ÷ (D + 4d) (two teeth in the cut).
- For another number of teeth in the cut, divide by 2 and multiply by that number.
- Power rule: T = K H ÷ (F N d W) (handbook example: 7.5 kW, 0.2032 mm, 272 rpm, 3.2 × 152.4 mm cut in alloy steel gives about 4 teeth).
- Example: a 152.4 mm face mill taking a 101.6 mm wide cut should have about 9.45 teeth (the handbook rounds this example to 10).
Limitations
- Guidance only; chip space, chatter and insert geometry also govern.
- The power rule protects the motor; it does not check chip space.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Choose a coarse or fine pitch cutter for a job
- Avoid overloading the spindle with too many teeth
- Check that enough teeth are in the cut to avoid chatter
Who it is for
- Machinists
- Toolmakers
- Manufacturing engineers
What you get
- Recommended number of teeth
- Basis of the recommendation
- Rounded tooth count
Interpreting the result
- Fewer teeth suit long-chipping materials and heavy cuts; more teeth suit thin walls and short-chipping materials.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 808–809. Topic reference; no source tables or recommended settings are reproduced.
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