Harbor Freight Cordless Drill Motor and BB Gearbox Conversion by dz1sfb

Last crawled date: 3 years ago

This project came as the result of wanting to have a ball bearing supported output shaft on my robot project for the this year. I originally employed a Harbor Freight cordless drills for drives on both sides of my 12 lb bot, as well as the weapon lift. You can use the stock gearbox housing, but it is only bushing supported, and would therefore require periodic greasing to keep things lubed and cool. The bottom line is that the HF gearbox is not designed for side loads that the driveline will impute to it.
So here it is; mountable from three different sides with M5 fasteners. The gearbox is held together with four M5 x 35mm long flat socket head screws. It is clearance at the joint to accept a 1.5" ID x 1.75" OD O-ring, helping to keep the grease inside the gearbox. I got them from the local hardware store for $0.65 ea. The motor attaches to the gearbox cover with the same fasteners as it was attached with the original gearbox. The 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, and I got them through Fastenal for $1.49 each. Two required per gearbox.
Total cost for the conversion not including shipping is;
Fasteners $0.92
O-ring $0.65
Bearings $2.98
PLA Filament $1.16
Total of $5.71
O-ring spec https://www.grainger.com/product/GRAINGER-APPROVED-Round-222-Medium-Hard-Neoprene-1BUX9
Bearings https://www.fastenal.com/products/details/0474374?term=bearing&r=~%7Ccategoryl1:%22603582%20Power%20Transmission%209and%20Motors%22%7C~%20~%7Ccategoryl2:%22610631%20Unmounted%20Bearings%22%7C~%20~%7Ccategoryl3:%22612457%20Ball%20Bearings%22%7C~%20~%7Ccategoryl4:%22610637%20Radial%209and%20Deep%20Groove%20Ball%20Bearings%22%7C~%20~%7Csattr01:%5E12mm$%7C~%20~%7Csattr02:%5E28mm$%7C~
Fasteners http://www.mrmetric.com/M10433
Here is the drill from Harbor Freight https://www.harborfreight.com/18-volt-38-in-cordless-drilldriver-with-keyless-chuck-21-clutch-settings-62873.html
You can modify the output shaft as desired. Mine is getting converted to a .375" Hex.