KEVOS® MAKEOS · Manufacturing
Thread Milling Tool Path and Feed
What tool-centre path and programmed feed does this helical thread milling operation need?
Tool-centre path diameter, programmed centre-line feed for the required feed at the cutting edge, helical path length per revolution and cycle time for internal or external thread milling.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Thread | choice | Internal or external thread. |
| Thread major diameter (internal) or major diameter (external) | mm | Major diameter of the thread (the cutting edge reaches this diameter for internal threads). |
| Pitch | mm | Thread pitch. |
| Cutter diameter | mm | Thread mill cutting diameter. |
| Spindle speed | rpm | Spindle speed. |
| Feed per tooth at the cutting edge | mm | Feed per tooth wanted at the cutting edge (from the tool maker). |
| Cutter flutes | flutes | Number of flutes. |
| Thread length | mm | Length of thread to mill (single-form cutters). |
| Radial passes | passes | Number of radial passes. |
Method and formulas
- Path diameter = D − dc (internal) or D + dc (external).
- Edge feed = rpm × z × fz; centre feed = edge feed × (D − dc)/D internal or (D + dc)/D external.
- Revolutions = thread length ÷ pitch per pass; time = revolutions × π × path diameter ÷ centre feed (plus entry and exit).
- Example: M20 × 2.5 internal with a 14 mm cutter: program 216 mm/min on a 6 mm path.
Limitations
- Single-form (one-tooth-row) thread mill; multi-form tools cut the whole length in one revolution.
- Arc entry and exit moves are not included in the time.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Program thread milling without a CAM system
- Correct feed for the cutter path
- Estimate thread milling cycle time
Who it is for
- Machinists
- CNC programmers
- Manufacturing engineers
What you get
- Tool-centre path diameter
- Feed at the cutting edge and programmed centre feed
- Helical revolutions and cycle time
Interpreting the result
- Many controls apply the centre-feed correction automatically when cutter compensation is used; check your control’s behaviour.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2063–2070, 1292–1300. Topic reference; no source tables or recommended settings are reproduced.
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