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Tapping Speeds and Feeds
Guide · Updated October 27, 2026
Tapping is where speeds and feeds stop being a suggestion. The feed has to match the thread pitch exactly, and the speed has to stay low enough for the tap to survive. Here's the tap drill rule, the formulas and worked inch and metric examples.
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Tap drill sizes (cutting taps, about 75% thread)
| Tap | Rule result | Common drill |
|---|---|---|
| 1/4-20 UNC | 0.200 in | #7 (0.201 in) |
| 5/16-18 UNC | 0.257 in | F (0.257 in) |
| 3/8-16 UNC | 0.3125 in | 5/16 in |
| M6 × 1 | 5.0 mm | 5.0 mm |
| M8 × 1.25 | 6.75 mm | 6.8 mm |
| M10 × 1.5 | 8.5 mm | 8.5 mm |
Formulas
- RPM: SFM × 3.82 ÷ D (in), or 1000 × Vc ÷ (π × D) (mm)
- Feed: IPM = RPM ÷ TPI, or mm/min = RPM × pitch
Conservative tapping speeds (HSS taps)
| Material | SFM | m/min |
|---|---|---|
| Aluminum | 50–100 | 15–30 |
| Mild steel | 20–40 | 6–12 |
| Stainless | 10–20 | 3–6 |
Starting points only; coated and carbide taps differ. Follow the tap maker's data.
Worked examples
- 1/4-20 in mild steel at 30 SFM: 30 × 3.82 ÷ 0.25 ≈ 458 RPM, and 458 ÷ 20 ≈ 22.9 IPM.
- M6 × 1 in mild steel at 10 m/min: 1000 × 10 ÷ (π × 6) ≈ 531 RPM, and 531 × 1 = 531 mm/min.
Step by step
- Pick the tap drill: Use major diameter minus pitch (1 ÷ TPI for inch), then round to the nearest standard drill.
- Drill and chamfer: Drill the hole to depth and chamfer the edge so the tap starts straight.
- Set tapping RPM: RPM = SFM × 3.82 ÷ D (in), or 1000 × Vc ÷ (π × D) (mm), using a slow tapping speed.
- Match feed to pitch: IPM = RPM ÷ TPI, or mm/min = RPM × pitch. Use rigid tapping or a tension-compression holder.
- Use tapping fluid: Use a cutting or tapping fluid, and in blind holes leave room below the threads for chips.
New to this? Start with drilling speeds and feeds and feeds and speeds basics.
FAQ
What size drill for a 1/4-20 tap?
A #7 drill (0.201 in) for about 75% thread. The quick rule is major diameter minus 1 ÷ TPI: 0.250 − 0.050 = 0.200 in.
What size drill for an M6 x 1 tap?
5 mm. For metric cutting taps, tap drill ≈ major diameter minus pitch: 6 − 1 = 5 mm.
What is the feed rate for tapping?
The feed must equal the pitch. IPM = RPM ÷ TPI, or mm/min = RPM × pitch. A 1/4-20 tap at 458 RPM feeds at 22.9 IPM.
How fast should I run a tap?
Much slower than a drill. For HSS taps, roughly 20 to 40 SFM in mild steel, 10 to 20 in stainless and 50 to 100 in aluminum, then follow the tap maker's data.
Does the drill rule work for form (roll) taps?
No. Form taps need a larger hole than cutting taps. Use the form tap maker's chart.
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