KEVOS® MAKEOS · Gears
Spur Gear Milling Set-up (Indexing, Cutter Number, Depth, Tooth Check)
How do I set up a dividing head and form cutter to mill this spur gear: index setting, cutter number, blank size, depth of cut and the chordal tooth check?
Set-up for milling a spur gear with a form cutter on a dividing head: simple indexing (crank turns and holes in an index circle) for the number of teeth (as the simple indexing tool), the involute cutter number for the tooth count (as the gear cutter number tool), blank outside diameter, whole depth of cut, and the chordal thickness and chordal addendum for checking the first teeth with a gear tooth vernier (as the chordal tooth tool).
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Module | mm | Module of the gear. |
| Number of teeth | Number of teeth to cut. | |
| Dividing head worm ratio | :1 | Turns of the index crank per turn of the spindle. |
| Index plates available | choice | Index plates on your dividing head. |
| Dedendum factor (dedendum ÷ module) | Dedendum as a multiple of the module (your gear standard); the addendum is one module. |
Method and formulas
- Crank turns = ratio ÷ z: whole turns plus holes in a circle where the remainder × circle ÷ z is whole (as the simple indexing tool).
- Cutter number from the tooth count (as the gear cutter number tool).
- Blank diameter = m (z + 2); depth of cut = m (1 + dedendum factor); chordal thickness = D sin(π ÷ 2z) and chordal addendum = m + D ÷ 2 [1 − cos(π ÷ 2z)] (as the chordal tooth tool).
- Example: index 0 turns and 40 holes in the 47-hole circle; use cutter No. 3; turn the blank to 98 mm and cut 4.5 mm deep.
Limitations
- Form cutters give approximately correct profiles; generated gears are more accurate.
- Simple indexing only; numbers it cannot divide need differential indexing.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Set up a milling machine to cut a replacement gear
- Check whether a tooth count can be simply indexed
- Prepare an operation sheet for gear cutting
Who it is for
- Machinists
- Toolroom staff
- Maintenance fitters
What you get
- Index setting
- Cutter number
- Blank diameter, depth of cut and chordal tooth check
Interpreting the result
- Check the first two teeth with the gear tooth vernier before cutting the rest.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2107–2121, 2148–2150, 2145, 2238–2240. Topic reference; no source tables or recommended settings are reproduced.
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Open the Spur Gear Milling Set-up (Indexing, Cutter Number, Depth, Tooth Check) calculator
