1:1 Right Angle Tapered Bevel Gearbox Mini 1 Module 20 Teeth 90° Angle Drive Steering Gear Device Simple Mechanical DIY Module with 8mm Shaft

A local business ask me to build them a cutting machine that needed an adjustable cutting height. I was surprised after a search & found this gearbox. I engineered a mounting location and pinned a threaded rod on one end and made a knurled knob for the opposite side. The gearbox worked great!

Good, but don't expect zero internal friction. Grease, not oil inside. Overall VERY nice and handy. There's a version with a solid shaft all the way through, or with 3 gears inside where the center shaft drives the other two in opposite directions from each other. Get the right one for your needs! But it won't be like a rear wheel drive car differential that drives those two shafts the same direction without them having to be the same rotational speed. That is a much more complicated design than these.

I bought these to link together with four shafts and four T-gear motors to raise and lower a cnc table's work platform. They are made well and VERY smooth!