Fwiw and down the road with the Servo you'd have some hope of continued parts support and repair. The Asian power feeds? Who knows just how long Shars might be around or if they even care about stocking parts for a design or what ever manufacturer they currently use that might be changed at any time. Finding someone who can supply parts tomorrow never mind 10 yrs later could be an issue if that might be important enough to you. It also depends on what condition your BP is in. Adding brand new Servo feeds to an almost worn out machine wouldn't be worthwhile. And Shars isn't an actual tool manufacturer since they don't make anything themselves, but there now large enough to have there name incorporated onto quite a bit by whoever is making it for them. There a tool supplier just like Jet, Grizzly etc. I have a 150 sized Asian unit on my BP clone's X axis, it's ok I guess, but I think less smooth and with a bit more noise than the few Servo feeds I've been around. I also suspect it's actual torque output might be a bit over stated. With my own hind sight compared to when I bought my mill, table feeds are used just about every time the mill is. And while I haven't had any real issues with mine yet, if I knew then what I do now, I most likely would have spent the extra and bought a Servo instead. I also don't automatically believe any user reviews about any product. Even more so if it's Asian. If they've never used anything better they don't really have anything to compare it to.
Going by a lot of different forum posts on various sites I think all or most of the Asian clones of the Servo feeds have universally poor mounting instructions. If you did buy those Shars feeds, I'd use Servo's own and much better instructions.
http://www.servoproductsco.com/specs/0200_80003.pdf Shimming the feed units pinion gear to the bevel gear for the correct tooth clearance is a pita, but imo the most important step. The easiest method I found was to de-grease that bevel gear and color it's tooth flanks with a felt tip marking pen, install and do a few full rotations, then remove the feed and check the engagement marking. The real Servo units are probably made with a lot tighter tolerances so there recommended .015"-.025" backlash numbers on the feed screw dial would work. With anything else I think it takes a lot more trial checks and adjustments to get correct. Keep adding / subtracting shims as required with further checks. The tightest engagement possible isn't better since adds much more load onto the motor and excessive gear tooth wear. And what most don't normally mention on the forums and YT videos is those shim stacks also allow some fine adjustment later once enough wear has taken place. I don't think there an install and then just ignore for the life of the machine accessory.
