CNCTOPBAOS NMRV030 Worm Gear Reducer Speed Ratio 40:1 RV30 NMRV-030 Worm Gearbox Speed Reducer Square Type for Nema23 Stepper Motor/Servo Motor NMRV30 Output Bore/Hole 14mm Shaft

This unit is super solid and is a great price for what you get. Gearbox comes fully lubricated and is factory sealed. so don't expect to open it easily (not that you'd need to). It's full of oil and you'd need to remove the rubber gasket without damaging it somehow. The biggest issue I had was finding the appropriate hardware for driving the input side of the gearbox. The main input has an odd inner diameter of 11mm (7/16") with a 4mm wide key and I underestimated how hard it would be to find appropriate components to drive this with a larger shaft. With that said, the manufacturer included coupler that adapts this down to an 8mm d-shaft and that fits standard sized servos traditionally used for this.

I have been using this worm gear with a stepper motor for a couple of years. It is well made and has been working flawlessly since I bought it. If you need a gear reduction for a stepper motor, I can highly recommend this one.

This was a good quality gearbox and the price was very good. Being used in a prototype to determine life.

I'm using this as a 4th axis on a cnc and need it to be as rigid and repeatable as possible so the lack of wiggle is fantastic

Looks solid but did not serve it's purpose. My understanding of worm gears is that you can (should be able to) turn the gear from one side only - the worm gear itself. Turns out that I can turn this one from either side! Completely defeated my purpose for buying it. I didn't even realize it until it was too late. Maybe some worm gears are like that. But they should say so.