CNCTOPBAOS NMRV30 Worm Gearbox Speed Reducer NMRV030 Worm Gear Reducer Speed Ratio 20:1 RV30 Square Type for Nema23 Stepper Motor Output Hole 14mm Shaft NMRV-030

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

I needed a Worm Gear Reducerand this was just what I was looking for. Very well made and affordable.

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.

Solidly built, smooth movement with no backlash, but I had to return two of them because the mounting holes for the NEMA 23 motor were on 49 mm centers, not the expected 47 mm (see the photo for the difference)

As others have said, the mounting holes on this gearbox DO NOT LINE UP WITH NEMA 23 STANDARD HOLES. I bought 4 of them hoping it would be OK. Also, the movement of the gears is quite stiff; definitely use with beefy steppers/servos if you can figure out how to get them to fit. Will be returning these for sure. Absolutely unusable.