23.62 inch / 600mm Ball Screw RM1204 SFU1204 (End Processing) with Metal Ball Screw Nut and BK10/BF10 End Supports for DIY CNC Machine and 3D Printer

Best ball screw nut to screw fit I've seen in the past year over a dozen or so Chinese ball screws from 12mm to 20mm. Once it was cleaned (yes YOU clean it) and lubricated (again YOU), the motion was consistent over the 400mm with little to no binding and no grit. The fit was great.. I'm used to having to repack the but with bigger balls to get a proper fit, but this one was spot on. For you newbies, you do not want it to just spin freely. Packaging was great and shipping time was quick. Now the bad.. how is it possible to send these out with diameters that do not fit inside the bearing blocks? They're oversized and will not go! Little bit of elbow grease fixed it but I don't understand how that slips through QC. Overall, great deal for the price.. but do not expect perfection.

Good: The bearing blocks, hardware are quite ok. Less than .0005" runout between the ball screw races and ball nut. Bad: operation to turn the screw ends down was done poorly. Bad surface quality. Chuck marks catch the ball nut at either end of travel on the screw. Heres the tir i got from the ball nut to either screw end .003" runout on fixed end. Nearly .005" on the floated end. If end user wishes? You can make a ball nut ball retainer on your 3d printer, take the nut off, clean up the screw and repack the nut. Can re-grind the ends also concentric to the ball nut and take down any holding/tooling marks with a stone and flex abbrasive. My other option was a used thk that cost 10x more. Little elbow grease saves a lot of money. Be aware what you're getting into.

This ball screw if one of the worst I've experienced. Out of the packaging it has a thick goo on the screw that must me removed to even get started. Some of it had melted off and soaked the cardboard box. after careful cleaning, the motion is still jerky and not smooth like it should be. There's a lot of resistance in movement of the bearing block. Might be ok to replace a simple leadscrew in a cheap 3d printer, but it's far from precision.