I recently purchased a very nice older example of the popular Rong-Fu mill (mine's an enco). despite the inherent design comprimises of the mill, I'm pretty pleased with what it's able to do. but... well, everyone wants more out of their equipment, right???
I found some very good information about these mills at Harbor Freight 8x12 and Sieg X2 Mini Mill, DRO, CNC Conversion Plans, Machining/Metalworking How-tos and Resources, specifically addressing how to remove the spindle and adjust the pre-load on the bearings. the website also had good guidance about swapping the stock belts with powertwist v-belts, which I intend to try: Grainger Dayton 2AC40A Round Column Mill Drill! Harbor Freight 8x12 and Sieg X2 Mini Mill, DRO, CNC Conversion Plans, Machining/Metalworking How-tos and Resources
anyway, the site does a great job of addressing some of these issues, but there's one I've noticed that I'm wondering if anyone else has experienc with. if I lock the pulleys and wiggle an installed tool, I notice just a little bit of play. not much, but there's just a little bit of rotational wiggle between the splines of the shaft and the nut/collar that attached the pulley to the drive arrangement. I don't know how much it is, probabably just 1 or 2 degrees of rotation, but it's definitely there. I'm an amature machinist at best, but I'd like to get other's opinions if this is a problem or not before I tear my machine apart and try to figure out a solution. I've been able to get decent finishes, but I think it could get even better with flycutters etc. if I were able to get more vibration out of the mill. it would be most useful if there were some kind of split nut arrangment to remove this play in the shaft, but from the parts diagrams it does not look adjustable.
I'm not sure if there IS a way to solve this issue. I suppose the splined shaft and/or the collar nut that rides on it could be replaced, neither would be an easy part to fabricate oneself. for critical cuts, I suppose I could slide a tapered rod down the spline from the top, and wedge it between the splines and the nut, but that hardly seems like a long term solution.
has anyone ever investigated this issue and designed a working solution? curious to hear from the experts on the board.
I have the Jet JMD15 version of that mill and mine does the same thing. I don't think it is much of an issue.
Mine is converted to CNC and the quill is never locked in place and I believe that is the root of my minor vibration problems.
Just so you know all the parts currently on my web site (in my sig) are made on that type of machine.