KEVOS® MAKEOS · Gears
Helical Gear Milling Set-up (Lead, Change Gears, Cutter, Indexing)
How do I set up a universal milling machine to cut this helical gear: lead and change gears, table swivel, cutter number and index setting?
Set-up for milling a helical gear with a form cutter on a universal dividing head: pitch diameter from the normal module, the lead of the helix and the change gears from the table lead screw to the dividing head with the lead error (as the helical milling tool), table swivel, the cutter number from the formative number of teeth (as the gear cutter number tool for helical gears), the simple indexing setting (as the simple indexing tool), blank diameter and depth of cut.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Normal module | mm | Normal module of the gear. |
| Number of teeth | Number of teeth. | |
| Helix angle | ° | Helix angle at the pitch diameter. |
| Lead of the machine | mm | Lead of the machine: table travel for one turn of the dividing head spindle with equal gears. |
| Change gears available | choice | Change gears you have. |
| Dividing head worm ratio | :1 | Worm ratio of the dividing head. |
| Index plates available | choice | Index plates you have. |
| Dedendum factor (dedendum ÷ module) | Dedendum as a multiple of the normal module. | |
| Largest lead error | % | Largest lead error you accept from the gear train. |
Method and formulas
- Pitch diameter D = m_n z ÷ cos β; lead = π D ÷ tan β; ratio driven ÷ driver = lead ÷ machine lead, best four-gear train from the set (as the helical milling tool).
- Formative teeth = z ÷ cos³ β → cutter number (as the gear cutter number tool); index setting from ratio ÷ z (as the simple indexing tool).
- Blank diameter = D + 2m_n; depth = m_n (1 + dedendum factor); swivel the table by the helix angle.
- Example: lead 376.99 mm with drivers 24 and 44, driven 28 and 56 (error 0.042547%); cutter No. 3; index 1 turns and 5 holes in the 15-hole circle.
Limitations
- Form cutters give approximate profiles; the formative tooth count only picks the nearest cutter.
- Gear fit on the quadrant and the hand of helix (swivel direction) must be checked on the machine.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Set up a universal mill to cut a replacement helical gear
- Check the lead error of the best gear train
- Choose the form cutter for a helical gear
Who it is for
- Machinists
- Toolroom staff
- Maintenance fitters
What you get
- Pitch diameter, lead and change gears
- Cutter number and indexing
- Blank diameter and depth
Interpreting the result
- If the lead error is too large, try the other gear set or a compound train with an idler change.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2060–2062, 2205, 2107–2121, 2148–2150. Topic reference; no source tables or recommended settings are reproduced.
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