📓 INTERACTIVE CALCULATOR

Coolant Pressure Drop Calculator

Estimate the pressure a gundrill or BTA tube loses to flow friction — the first step in sizing the high-pressure pump so the tool tip still sees cutting pressure.

CALCULATOR

Line Pressure Drop (Darcy–Weisbach)

Flow rate (L/min)

Coolant passage ID (mm)

Tube length (mm)

Fluid

—

m/s

Flow velocity

—

Reynolds number

—

bar

Pressure drop

—

psi

Pressure drop

Assumes a straight circular passage and smooth wall. Real gundrill tubes have a D-shape passage and fittings — add 20–40% for a conservative sizing margin.

FORMULAS

How It's Calculated

Velocity v (m/s)= flow(m³/s) / (π/4 × d²)

Reynolds Re= ρ × v × d / μ

Friction factor f= 64/Re (laminar) or 0.316/Re^0.25 (turbulent)

Pressure drop Δp (Pa)= f × (L/d) × (ρv²/2)

⚠️ Tip pressure is what matters: the spec on a gundrill is the pressure at the drill tip. If the line loses 30 bar over a long tube, the pump must supply cutting pressure + 30 bar. Size accordingly — see the Coolant System Guide.