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Just 'Cuz Robotics

12mm Hex Hubs Pair, 4mm Bore (for DartBox & More)

12mm Hex Hubs Pair, 4mm Bore (for DartBox & More)

Regular price $15.00
Regular price Sale price $15.00
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These hex hubs are perfect for mounting wheels or 3D printed custom parts to 4mm motor shafts such as our very own DartBox Gearmotors. Made from strong yet lightweight 6061 aluminum, at 1/3rd the weight of brass or steel, these hubs will fit in well on almost any bot with direct-driven wheels! There are two extra tapped holes for inserting long set screws or normal M4 screws on the hex side to help secure narrower wheels, gears, pulleys, and more. And unique to these hubs is a precision turned 12mm diameter for adding bearing (sold here) or bushing support to protect otherwise fragile direct-driven wheel setups.
Each package contains two (2) hubs, two (2) M4 x 10mm flat head screws, and four (4) M4 x 4mm set screws! 

NOTE: Starting in November 2023 these hubs no longer have a thread on the end, they will have a 4mm straight bore all the way through. They might also come with 4 set screws installed in each hub - you may need to back them out to insert the hub into your motor shaft or remove those you aren't using. 

These hubs are compatible with:

  • DartBox Viper & Dragon Drive and HR 4mm Gearmotors
  • DartBox Gecko 4mm
  • Servocity Premium Planetary Gear Motor
  • Servocity Econ Spur Gear Motor
  • Rectified Robotics Brushless Gearmotor
  • Botkits 22mm DC Gearmotor
  • Double Geared 25mm Motors
  • Any other 4mm shaft motors!

Note: These can be drilled out to a through bore 4mm to slide down a motor shaft, which is required for use with an SSP kit. Or even drilled to 6mm to support our 6mm shaft upgrade for DartBox Drive or other 6mm shaft motors.
CAD model included here.


  • Material: 6061 Aluminum, strong and lightweight
  • Total Length: 18 mm (0.71 in)
  • Weight: <5 grams each with two set screws, <10 grams (0.352 oz) per pair!
  • 12mm hex, compatible with many off-the-shelf or custom wheels!
  • 4mm round bore
  • Short M4 x 4mm set screws on the rear section
  • Precision turned 12mm diameter for bushing or bearing support! (bearings sold separately)
  • Longer set screws (not included) can be used to secure custom wheels, gears, pulleys, etc on the hex end
  • Included flathead screw can be used to secure wheels, pullies, etc from sliding off the end
  • CAD Model Download Here
  • Drawing below, all dimensions in mm

drawing 4mm hex hub

    Note: these hubs have a 4mm bore perfect for DartBox Gearmotor 4mm shafts. If you need to use these with a 6mm shaft, try our 6mm hex hubs! For larger shafts, they can be drilled. Insert the 4mm screw into the end before drilling to keep those threads, or drill the whole thing out to fit it onto a longer shaft. DartBox gearmotors and bearings are not included.

    Customer Reviews

    Based on 1 review
    Chad Jones
    Multi-Purpose Hex Hubs

    Bought quite a few sets of these 12mm Hex Hubs to incorporate into my 4-WD wheel hub assemblies. They are another example of careful designing and thorough manufacturing. I drilled out several to fit my Viper 6mm drive shaft. Enjoying the extra set screw mounts for the longer screws I need to have with my wheels. I have yet to use a bearing with these but the hex design helps to align itself into the wheel hub.

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