Important formulas
Cutting speed and rotational speed
v = (D・π・n) : (π)
n = (v・1000) : (D・π)
n = speed (rpm)
v = cutting speed (m/min)
D = nominal diameter (mm)
Calculation of the core hole Ø
d4 = D - P*
D = nominal diameter (mm)
P = pitch
* not valid for TR, RD or conical threads
Oversize on the tap for a given coating thickness
h = 2・(a : sin α)
a = layer thickness
α = 1/2 flank angle
sin 30° = 0.5
sin 27.5° = 0.461
sin 15° = 0.259
Calculation of chip thickness
ae = (P2・0.5) : (z・l4)
P = Pitch
z = Number of grooves
l4 = Gate length
Calculation of forces during thread cutting
MD = (kc・h2・d1) : (8000) Nm
P = (MD・n) : (9500) kW
Pm = (P) : (ηM) kW
kc = Specific cutting force N/mm² according to table
h = Thread pitch
d1 = Nominal Ø (m)
n = Speed (rpm)
Pm = Required machine drive power
ηM = Machine efficiency
Conversion inch to mm
1 inch = 25.4 mm
> for example, 28 whole per inch correspond = approx. 0.90 mm
| Material | Rm/UTS (N/mm2) | Kc-Valor(N/mm2) |
| Unalloyed structural steel | -700 | 2300 |
| Free cutting steel | -700 | 2300 |
| Structural steel | 500-950 | 2500 |
| Quenched and tempered steel, medium strength | 500-950 | 2600 |
| Nitriding beam, quenched and tempered | 950-1400 | 3600 |
| Tool steel | 950-1400 | 3600 |
| Stainless and acid resistant steel austenitic | 500-950 | 3200 |
| Aluminum alloys, long-chipping | -550 | 800 |
| Copper alloys, long-chipping | 300-700 | 1100 |
| Gray cast iron | 100-400 (120-260 HB) | 1250 |
| Alloy gray cast iron | 150-250 (160-230 HB) | 1600 |
| Malleable cast iron | 350-700 (150-280 HB) | 1100 |
| Aluminum alloys, short-chipping | -400 | 680 |
| Copper alloys, short-chipping | -500 | 720 |