Sandvik Coromant logo
  • close
  • Productschevron_right
  • Learningchevron_right
  • Manufacturing solutionschevron_right
  • Supportchevron_right
  • chevron_left Back
    close
  • chevron_left Back
    close
  • chevron_left Back
    close
account_circleshopping_cart
menu
Machining formulas and definitions
Machining formulas and definitionsexpand_more
Machining formulas and definitions
Machining formulas and definitionsexpand_more

Turning formulas and definitions

When machining in lathes, turning centres or multi-task machines, calculating the correct values for different machining parameters like cutting speed and spindle speed is a crucial factor for good result. In this section you find the formulas and definitions needed for general turning.

Cutting speed vc (m/min)

𝑣𝑐=𝐷𝑚⋅𝜋⋅𝑛1000

Cutting speed vc (ft/min)

\[ v_c = \frac{D_m \cdot \pi \cdot n}{12} \]

Spindle speed n (rpm)

\[ n = \frac{v_c \cdot 1000}{\pi \cdot D_m} \]

Spindle speed n (rpm) (Inch)

\[ n = \frac{v_c \cdot 12}{\pi \cdot D_m} \]

Metal removal rate Q (cm3/min)

\[ Q = v_c \cdot a_p \cdot f_n \]

Metal removal rate Q (inch3/min)

\[ Q = v_c \cdot a_p \cdot f_n \cdot 12 \]

Net power Pc (kW)

\[ P_c = \frac{v_c \cdot a_p \cdot f_n \cdot k_c}{60 \cdot 10^3} \]

Net power Pc (HP)

\[ P_c = \frac{v_c \cdot a_p \cdot f_n \cdot k_c}{33 \cdot 10^3} \]

Machining time Tc (min)

\[ T_c = \frac{l_m}{f_n \cdot n} \]



SymbolDesignation/definationUnit, metric (imperial)
Dm​Machined diameter mm (inch)​mm (inch)​
fnFeed per revolution​mm/r (inch/r)​
ap​Cutting depth​mm (inch)​
vcCutting speed​m/min (feet/min)​
nSpindle speedrpm​​
Pc​Net powerkW (HP)
QMetal removal ratecm3/min (inch3/min)
hm​Average chip thickness​mm (inch)
hexMaximum chip thicknessmm (inch)
Tc​Period of engagement​min​
lmMachined length​mm (inch)
kc​Specific cutting forceN/mm2 (N/inch2)
KAPR​Entering angledegree​
PSIR​​Lead angle​degree​
Tangential force, Ft
\[ F_t = k_{c,D,A} \cdot \left(\frac{0.4}{f_n}\right)^{0.29} \cdot f_n \cdot A_P \]

Kc 0,4: Specific cutting force at feed 0,4 mm/r
mc: Constant, depending on material. Use 0,29 as general value.

Tangential force, simplified formula
\[ F_t = k_{c,D,A} \cdot \left(\frac{0.4}{f_n \cdot \sin(\text{KAPR})}\right)^{m_c} \cdot f_n \cdot A_P \]

When the entering angle (KAPR) is 75 degrees or longer, sin KAPR is ~1. Then this simplified formula can be used.

Rule of thumb: Ft should not exceed 90% of maximum load stated for the bar used.


All turning tools

Explore the assortment chevron_right

Want to learn more about the metal cutting basics?

Register for our free e-learning programme chevron_right

Unsure which tool to choose?

View our selection of recommended tools and cutting data chevron_right

account_circle
Create account chevron_right

Place orders, view prices and check tool availability

mail
Subscribe to our newsletter chevron_right

Join us. Stay updated.