Harbor Freight Cordless Drill Motor and BB Gearbox Conversion

thingiverse

This project was born out of a desire for my robot project this year to have a ball bearing supported output shaft. Initially, I used a Harbor Freight cordless drill as the drive on both sides of my 12 lb bot, as well as the weapon lift. The stock gearbox housing can be employed, but it is only bushing supported, requiring periodic greasing to keep things lubricated and cool. Unfortunately, the HF gearbox isn't designed for side loads that the driveline will impose on it. So here's the solution; a mountable gearbox from three different sides with M5 fasteners. The gearbox is held together with four M5 x 35mm long flat socket head screws. Clearance at the joint allows for a 1.5" ID x 1.75" OD O-ring to keep the grease inside the gearbox. I purchased these O-rings from my local hardware store for $0.65 each. The motor attaches to the gearbox cover with the same fasteners as it was attached with the original gearbox. An original snap ring and one of the thrust washers completes the assembly with minimal endplay. The bearings are 28mm OD x 12mm ID x 8mm high shielded, obtained through Fastenal for $1.49 each; two required per gearbox. The total cost for this conversion, excluding shipping, is as follows: Fasteners: $0.92 O-ring: $0.65 Bearings: $2.98 PLA Filament: $1.16 Total: $5.71 You can refer to the O-ring specifications here: https://www.grainger.com/product/GRAINGER-APPROVED-Round-222-Medium-Hard-Neoprene-1BUX9 The bearings can be found at: https://www.fastenal.com/products/details/0474374?term=bearing&r=~%7Ccategoryl1:%22603582%20Power%20Transmission%209and%20Motors%22%7C~%20~%7Ccategoryl2:%22610631%20Unmounted%20Bearings%22%7C~%20~%7Ccategoryl3:%22612457%20Ball%20Bearings%22%7C~%20~%7Ccategoryl4:%22610637%20Radial%209and%20Deep%20Groove%20Ball%20Bearings%22%7C~%20~%7Csattr01:%5E12mm$%7C~%20~%7Csattr02:%5E28mm$ Fasteners can be found at: http://www.mrmetric.com/M10433 You can refer to the Harbor Freight drill used here: https://www.harborfreight.com/18-volt-38-in-cordless-drilldriver-with-keyless-chuck-21-clutch-settings-62873.html Feel free to modify the output shaft as desired; mine is being converted to a .375" Hex.