KEVOS® MAKEOS · Manufacturing
Thread Milling Plan (Speed, Feeds, Radial Passes and Batch Time)
What spindle speed and programmed feed does this thread mill need, how many radial passes for the depth, and how long will a batch of threads take?
Plan of helical thread milling with a single-form or multi-form cutter: spindle speed from cutting speed (held to the machine maximum), feed at the cutting edge, tool-centre path diameter and the programmed centre feed corrected for the path (as the thread milling path tool), radial passes for the thread depth at your largest radial step, milling time per thread and for the batch with approach and retract time, and the cutter-size check for internal threads.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Thread | choice | Internal (in a hole) or external (on a boss) thread. |
| Major diameter | mm | Major diameter of the thread. |
| Pitch | mm | Pitch. |
| Thread length | mm | Length of thread to mill. |
| Cutter diameter | mm | Cutting diameter of the thread mill. |
| Cutter flutes | Number of cutting flutes. | |
| Cutting speed | m/min | Cutting speed for the cutter and material. |
| Feed per tooth (at the cutting edge) | mm | Feed per tooth at the cutting edge. |
| Largest spindle speed | rpm | Highest spindle speed. |
| Largest radial depth per pass | mm | Largest radial depth the cutter takes in one pass (your value for the cutter and material). |
| Approach, arc-in and retract per thread | s | Time for approach, arc-in, arc-out and retract per thread. |
| Threads in the batch | Number of threads in the batch. |
Method and formulas
- n = min(1000 v_c ÷ π d_c, n_max); edge feed f_e = n z f_z.
- Path diameter = D − d_c (internal) or D + d_c (external); centre feed f_c = f_e × path diameter ÷ D (as the thread milling path tool).
- Thread depth = 0.5413P (internal) or 0.6134P (external); radial passes = depth ÷ largest step (rounded up).
- Time per thread = (L ÷ P × passes) × helix length ÷ f_c + approach; batch = threads × time.
- Example: 2,728.4 rpm with a programmed feed of 196.44 mm/min mills the thread in 2 passes, 120.15 s per thread.
Limitations
- Single-form cutter making one helix per pass; multi-form cutters cover several pitches per revolution.
- Deflection of long, small cutters may need extra spring passes.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Program a thread milling cycle
- Compare thread milling with tapping for a batch
- Check cutter size for a small internal thread
Who it is for
- CNC programmers
- Process planners
- CNC machinists
What you get
- Spindle speed, edge feed and programmed centre feed
- Radial passes and helical revolutions
- Time per thread and for the batch
Interpreting the result
- Forgetting the path-diameter correction overfeeds an internal thread by the ratio D ÷ (D − d_c).
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2058–2070, 1292–1300. Topic reference; no source tables or recommended settings are reproduced.
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Open the Thread Milling Plan (Speed, Feeds, Radial Passes and Batch Time) calculator
