DIY External Gear Drill Pump

This is a complete DIY External Gear Drill Pump project – a compact, portable positive displacement pump that uses a standard cordless drill as the power source (no motor, no batteries).

-> animated FreeCAD file incl.

Key Features

• Flow rate: up to ~2 L/min (depending on drill RPM) [measured at 20 cm vertical suction]

• Total weight equipped (with brass plugs + 20 cm hose): 211 g (core pump < 200 g)

• Gears: quadruple helical (35° helix angle) – printed in PETG, Ø 22.5 mm × 20 mm height, extremely low noise and pulsation

• Watertight: 15 mm wall thickness housing with integrated TPU flex seals, Dichtol impregnation (seals pores < 0.1 mm), and precise 0.2 mm air gap jig

• Visual monitoring: CNC-machined transparent acrylic (PMMA) top

• Assembly: only 14 parts total, including 6× M4×8 mm screws, 2× SKF 608-2RSH sealed bearings, 2× 8 mm aluminum axles (50.00 mm & 25.10 mm length, ground to D-shape)

• Power: attaches directly to drill chuck

• Noise: None. You only hear the power drill. Period.

Print Settings (recommended)

• Material: PETG (good lubrication & water resistance)

• Layer height: 0.1–0.15 mm (gears); rest: 0.2–0.25 mm

• Perimeters: 4+

• Infill: 25 % (3D honeycomb)

• Supports: only for the case, preferably organic

• Post-processing: Apply Dichtol (by Diamant Polymer Solutions) impregnator for full waterproofing

Included Files

• .3mf full assembly

• .3mf files for all printable parts 

• .dxf file for acrylic top

• .FCStd full assembly file (motion, exploded view, etc.)

Additional Materials and Tips for Success
For best results and durability, consider these optional extras:

• Brass screwing plugs (G1/4" thread, ~13 mm outer diameter) for secure, corrosion-resistant inlet/outlet connections

• 20 cm flexible tube for practical fluid transfer

• Epoxy glue – apply it sparingly to the outside of the screw holes around the brass plugs to stiffen that area and better distribute the force transmitted to the housing wall. Otherwise, the layers may crack, so screw them in carefully.
  Besides that, use it to secure the bearings on the gear axles and to bond the bearings into the case

• Transparent sealing glue (clear silicone adhesive) for extra edge sealing if needed

• PTFE tape (Teflon thread seal tape) – wrap 1 turn on brass plug threads for leak-free connections

• Silicone spray – light application to gears and axles after printing to further reduce friction and improve long-term smoothness

Tested with water – primes easily, no leaks observed. Oil/viscous fluids should work even better. Open for remixes, improvements, or variants (different flow rates, materials). Feedback welcome!

License: Creative Commons – Attribution (CC-BY 4.0) – feel free to share, modify, and use commercially with credit.

Print, pump, enjoy! 🚀