Important formulas
Cutting speed and rotational speed
v = (D・π・n) : (π)
v = (v・1000) : (D・π)
n = Machine rotation speed (r/min)
v = Cutting speed (m/min)
D = Nominal diameter (mm)
Calculation of the core hole Ø
d4 = D - P*
D = Nominal diameter (mm)
P = Pitch
* Does not apply to TR / Rd or chonical 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 oversize corresponding to the layer thickness
ae = (P2・0,5) : (z・l4)
P = Pitch
z = Number of flutes
l4 = Length of entry
Torques and power range
MD = (kc・h2・d1) : (8000) Nm
P = (MD・n) : (9500) kW
Pm = (P) : (ηM) kW
kc = Cuting Force (Nmm2) (acc. to able)
h = Thread pitch
d1 = Nominal diameter (m)
n = Rotation speed (rpm)
Pm = Required machine drive power
ηM = Machine efficiency
| Material | Rm/UTS (N/mm2) | Kc-Value (N/mm2) |
| Unalloyed construction metal | -700 | 2300 |
| Free cutting steel | -700 | 2300 |
| Structural steel | 500–950 | 2500 |
| Medium strength tempered steel | 500–950 | 2600 |
| Nitrided tempered steel | 950–1400 | 3600 |
| Tool steel | 950–1400 | 3600 |
| Stainless and acid resistant steel, austenitic | 500–950 | 3200 |
| Aluminium alloys, long chipping | -550 | 800 |
| Copper alloys, long-chipping | 300–700 | 1100 |
| Grey cast iron | 100–400 (120–260 HB) | 1250 |
| Alloy grey cast iron | 150–250 (160–230 HB) | 1600 |
| Malleable cast iron | 350–700 (150–280 HB) | 1100 |
| Aluminium alloys, short-chipping | -400 | 680 |
| Copper alloys, short-chipping | -500 | 720 |
Conversion inch to mm
1 Inch = 25,400 mm
> e.g. pitch of 28 TPI = 0,90 mm