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Important formulas

Cutting speed and rotational speed

v = (Dπn) : (π)

v = (v1000) : (Dπ)

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 = (P20,5) : (zl4)

P = Steigung
z = Nutenzahl
l4 = Anschnittlänge

Torques and power range

MD = (kch2d1) : (8000) Nm

P = (MDn) : (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

MaterialRm/UTS (N/mm2)Kc-Value (N/mm2)
Unalloyed construction metal-7002300
Free cutting steel-7002300
Structural steel500–9502500
Medium strength tempered steel500–9502600
Nitrided tempered steel950–14003600
Tool steel950–14003600
Stainless and acid resistant steel, austenitic500–9503200
Aluminium alloys, long chipping-550800
Copper alloys, long-chipping300–7001100
Grey cast iron100–400 (120–260 HB)1250
Alloy grey cast iron150–250 (160–230 HB)1600
Malleable cast iron350–700 (150–280 HB)1100
Aluminium alloys, short-chipping-400680
Copper alloys, short-chipping-500720

Conversion inch to mm

1 Zoll = 25,400 mm

> e.g. pitch of 28 TPI = 0,90 mm