Single Point Threading In-Feed Distances
The tables below give information on how far to feed a tool in when cutting a thread with a single-point tool on a lathe. External and internal columns are (unsurprisingly) for external and internal threads; straight and angled columns depend on whether you're feeding with the cross-slide (straight) or with a top-slide angled at 30° (angled). In practice, it's probably always worth checking against a reference thread, but I find this table to be a good start.
If doing a non-standard thread (e.g. M12×1), just pick an entry with the same pitch and the values should be the same.
I have these tables available as a printable PDF. Please get in touch if you're interested and I'm happy to email a copy to you.
Full thread form tool (numbers in brackets are for diameter-reading cross-slides):
Thread | Pitch | External Straight | External Angled | Internal Straight | Internal Angled |
---|---|---|---|---|---|
M2 | 0.4 mm | 0.25 mm (0.50 mm) | 0.28 mm | 0.22 mm (0.44 mm) | 0.25 mm |
M2.5 | 0.45 mm | 0.28 mm (0.56 mm) | 0.32 mm | 0.24 mm (0.48 mm) | 0.28 mm |
M3 | 0.5 mm | 0.31 mm (0.62 mm) | 0.35 mm | 0.27 mm (0.54 mm) | 0.31 mm |
M4 | 0.7 mm | 0.43 mm (0.86 mm) | 0.50 mm | 0.38 mm (0.76 mm) | 0.44 mm |
M5 | 0.8 mm | 0.49 mm (0.98 mm) | 0.57 mm | 0.43 mm (0.86 mm) | 0.50 mm |
M6 | 1.0 mm | 0.61 mm (1.22 mm) | 0.71 mm | 0.54 mm (1.08 mm) | 0.63 mm |
M8 | 1.25 mm | 0.77 mm (1.54 mm) | 0.89 mm | 0.68 mm (1.36 mm) | 0.78 mm |
M10 | 1.5 mm | 0.92 mm (1.84 mm) | 1.06 mm | 0.81 mm (1.62 mm) | 0.94 mm |
M12 | 1.75 mm | 1.07 mm (2.14 mm) | 1.24 mm | 0.95 mm (1.90 mm) | 1.09 mm |
M16 | 2.0 mm | 1.23 mm (2.46 mm) | 1.42 mm | 1.08 mm (2.16 mm) | 1.25 mm |
M20 | 2.5 mm | 1.53 mm (3.06 mm) | 1.77 mm | 1.35 mm (2.70 mm) | 1.56 mm |
Sharp tipped tool (numbers in brackets are for diameter-reading cross-slides):
Thread | Pitch | External Straight | External Angled | Internal Straight | Internal Angled |
---|---|---|---|---|---|
M2 | 0.4 mm | 0.30 mm (0.60 mm) | 0.35 mm | 0.26 mm (0.52 mm) | 0.30 mm |
M2.5 | 0.45 mm | 0.34 mm (0.68 mm) | 0.39 mm | 0.29 mm (0.58 mm) | 0.34 mm |
M3 | 0.5 mm | 0.38 mm (0.76 mm) | 0.44 mm | 0.32 mm (0.64 mm) | 0.38 mm |
M4 | 0.7 mm | 0.53 mm (1.06 mm) | 0.61 mm | 0.45 mm (0.90 mm) | 0.52 mm |
M5 | 0.8 mm | 0.61 mm (1.22 mm) | 0.70 mm | 0.52 mm (1.04 mm) | 0.60 mm |
M6 | 1.0 mm | 0.76 mm (1.52 mm) | 0.88 mm | 0.65 mm (1.30 mm) | 0.75 mm |
M8 | 1.25 mm | 0.95 mm (1.90 mm) | 1.09 mm | 0.81 mm (1.62 mm) | 0.94 mm |
M10 | 1.5 mm | 1.14 mm (2.28 mm) | 1.31 mm | 0.97 mm (1.94 mm) | 1.13 mm |
M12 | 1.75 mm | 1.33 mm (2.66 mm) | 1.53 mm | 1.14 mm (2.28 mm) | 1.31 mm |
M16 | 2.0 mm | 1.52 mm (3.04 mm) | 1.75 mm | 1.30 mm (2.60 mm) | 1.50 mm |
M20 | 2.5 mm | 1.89 mm (3.78 mm) | 2.19 mm | 1.62 mm (3.24 mm) | 1.88 mm |
Notes
Full thread form tool values are for tools that have the correct tip radius for the thread pitch being cut, for example if you're using a 16 ER 1.50 ISO insert in a holder. Sharp tipped tool values are for where you're using a tool ground to a 60° point (something I'd only recommend for very fine pitch threads due to the risk of tip breakage). If using a hand ground radius or a partial profile insert (like a 16 ER AG60 insert), the in-feed distances will be somewhere between the values in the two tables, depending on the tip radius.
For more detailed information, see "Thread tolerances" table on page 207 of Mechanical & Metal Trades Handbook as this is a better guide where available.
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