Machining

Machining force and spindle-power estimate

A first machine-tool check links the uncut chip area to cutting force, cutting power and required drive power. It is an engineering estimate for selecting and checking a process—not a substitute for tool-maker data or a machine capability curve.

Step	Turning estimate	Engineering check
Chip area	A = a_p · f	Use cutting depth and feed per revolution in millimetres; the result is in mm².
Chip thickness	h = f · sin κ_r	The cutting-edge angle changes chip thickness and therefore the applicable specific cutting force.
Cutting force	F_c = A · k_c · C	Select k_c for the work material and chip thickness; apply the stated correction factor.
Cutting power	P_c = F_c · v_c / 60,000	With force in N and speed in m/min, power is obtained in kW.
Required drive power	P₁ = P_c / η	Use the relevant machine efficiency and retain margin for the actual duty cycle.

ILLUSTRATIVE ESTIMATE

Check a turning operation

Assume a_p = 2.0 mm, f = 0.20 mm/rev, k_c = 2,500 N/mm², C = 1.0, v_c = 120 m/min and η = 0.80. Then A = 0.40 mm², F_c ≈ 1,000 N, P_c ≈ 2.0 kW and P₁ ≈ 2.5 kW.

RELEASE CHECK

Do not stop at motor rating

Confirm that the spindle can deliver the required torque at the selected speed.
Check tool, holder, workholding and machine rigidity against the estimated force.
Use process-specific equations for drilling or milling; tooth engagement and edge count change the load model.
Validate the final parameters with tool data, machine limits and a controlled trial cut.

Sources

Source basis: Ulrich Fischer et al., Mechanical and Metal Trades Handbook, 3rd English edition, machining-process overview and forces/power, print pp. 293–297; force and power relationships cross-checked against the corresponding 2nd-edition section, pp. 298–300. Worked values are an original application example.

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