Machining
Threads and tap drills
In short
Tap drill for cutting or forming taps, pitch and minor Ø, depth: M, UNC/UNF, G, Rp, Rc, NPT. Example with the default values: Tap drill = 8.50 mm.
Calculation
Example calculated with the tool’s default values.
Inputs
- Thread
- ISO metric (M)
- Size
- M10
- Tapping
- Cutting tap
- Hole
- Blind (form C tap)
Results
- Tap drill
- 8.50 mm
- Drilling depth (118° point)
- 22.1 mm
Worked example
Every value in this section belongs to the example, calculated with the tool’s default values.
Other results of the example
- Pitch
- 1.500 mm
- Major Ø
- 10.000 mm
- Pitch Ø (basic)
- 9.026 mm
- Minor Ø 6H min
- 8.376 mm
- Minor Ø 6H max
- 8.676 mm
- Thread engagement
- 77%
- Forming tap drill (65 %)
- 9.34 mm
- Tapping depth
- 19.5 mm
Step-by-step calculation
Pitch diameter
d2 = d − 0.649519 · P
10.000 − … × 1.500 = 9.026 mm
Basic minor diameter
D1 = d − 1.082532 · P
10.00 − 1.0825 × 1.500 = 8.376 mm
Thread percentage
% = (d − foret) / (1.299 · P)
(10.000 − 8.50) / (1.299 × 1.500) = 77 %
Forming tap drill
Ø = d − 0.0068 · 65 · P
10.000 − 0.0068 × 65 × 1.500 = 9.34 mm
Tapping depth
L + 3 · P (entrée C)
15.0 + 4.50 = 19.5 mm
Drilling depth
+ point = (Ø/2) / tan 59°
19.5 + 2.6 = 22.1 mm
ISO metric: tap drills
| Thread | Pitch (mm) | Cutting (mm) | Forming (mm) | D1 6H min–max |
|---|---|---|---|---|
| M2 | 0.40 | 1.60 | 1.82 | 1.567–1.679 |
| M2.5 | 0.45 | 2.05 | 2.30 | 2.013–2.138 |
| M3 | 0.50 | 2.50 | 2.78 | 2.459–2.599 |
| M3.5 | 0.60 | 2.90 | 3.23 | 2.850–3.010 |
| M4 | 0.70 | 3.30 | 3.69 | 3.242–3.422 |
| M5 | 0.80 | 4.20 | 4.65 | 4.134–4.334 |
| M6 | 1.00 | 5.00 | 5.56 | 4.917–5.153 |
| M8 | 1.25 | 6.80 | 7.45 | 6.647–6.912 |
| M10 | 1.50 | 8.50 | 9.34 | 8.376–8.676 |
| M12 | 1.75 | 10.20 | 11.23 | 10.106–10.441 |
| M14 | 2.00 | 12.00 | 13.12 | 11.835–12.210 |
| M16 | 2.00 | 14.00 | 15.12 | 13.835–14.210 |
| M18 | 2.50 | 15.50 | 16.90 | 15.294–15.744 |
| M20 | 2.50 | 17.50 | 18.90 | 17.294–17.744 |
| M22 | 2.50 | 19.50 | 20.90 | 19.294–19.744 |
| M24 | 3.00 | 21.00 | 22.67 | 20.752–21.252 |
| M27 | 3.00 | 24.00 | 25.67 | 23.752–24.252 |
| M30 | 3.50 | 26.50 | 28.45 | 26.211–26.771 |
| M33 | 3.50 | 29.50 | 31.45 | 29.211–29.771 |
| M36 | 4.00 | 32.00 | 34.23 | 31.670–32.270 |
| M8x1 | 1.00 | 7.00 | 7.56 | 6.917–7.153 |
| M10x1 | 1.00 | 9.00 | 9.56 | 8.917–9.153 |
| M10x1.25 | 1.25 | 8.80 | 9.45 | 8.647–8.912 |
| M12x1.25 | 1.25 | 10.80 | 11.45 | 10.647–10.912 |
| M12x1.5 | 1.50 | 10.50 | 11.34 | 10.376–10.676 |
| M14x1.5 | 1.50 | 12.50 | 13.34 | 12.376–12.676 |
| M16x1.5 | 1.50 | 14.50 | 15.34 | 14.376–14.676 |
| M18x1.5 | 1.50 | 16.50 | 17.34 | 16.376–16.676 |
| M20x1.5 | 1.50 | 18.50 | 19.34 | 18.376–18.676 |
| M22x1.5 | 1.50 | 20.50 | 21.34 | 20.376–20.676 |
| M24x2 | 2.00 | 22.00 | 23.12 | 21.835–22.210 |
| M27x2 | 2.00 | 25.00 | 26.12 | 24.835–25.210 |
| M30x2 | 2.00 | 28.00 | 29.12 | 27.835–28.210 |
| M33x2 | 2.00 | 31.00 | 32.12 | 30.835–31.210 |
| M36x3 | 3.00 | 33.00 | 34.67 | 32.752–33.252 |
Limits
Indicative results: they replace neither the applicable standards nor the job drawings and instructions. Check the values entered and the result before doing the work.
Sources
- ISO 2306 / ISO 724 (repris dans src/calc/data/threads.ts) : Forets avant taraudage, pas gros et pas fins ; d2 = d − 0,6495 P, D1 = d − 1,0825 P
- Vargus, ISO Metric Thread Dimensions 6g/6H : D1 mini / maxi 6H (tolérance TD1 par pas) (link)
- Made Good Designs, Tap drill chart : UNC/UNF classe 2B ; taraud à refouler d − 0,0068 · % · P (65 %) (link)
- ISO 228-1:2000, tableau 1 : Filetage G : D, pas, D1, TD1 (link)
- Utilities Bunker, Pipe thread tap drill chart : Forets G et Rp (Emuge), Rc (FWB), NPT (link)
- Sutton Tools, Tapping drill size chart : Rc 1:16 : foret seul et foret + alésoir (recoupe FWB) (link)
- DIN 2197 (Lubero, Baer) : Longueur d’entrée des tarauds : B 3,5–5,5, C 2–3, E 1,5–2 filets (link)
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