On 9/28/2014 8:35 PM, Gene Heskett wrote: > I too have a similar problem with my toy 7x12. And because the gibs are a > cast iron bitch to adjust, I've considered pulling the no longer used > rack, and adding an at least as long as the H wings bar front and back and > putting small ball bearings on some sort of adjusters to ride the bottom > of the front lip and back lip, which should reduce the friction from > trying to keep the gibs tight enough. Its slightly compounded on this > early 7x12 as the angle faces on the front of the way, and the angle cut > in the saddle didn't match by several degrees. With a front gib pulled up > tight, and the rear one off, the back of the H is lifted, originally about > 3/16", now maybe 5 thou. > > I milled that out to a better fit and its wearing in nicely over the last > 5 years, nearly stabilized. But with a QC toolpost, the offset from the > hold down bolt causes the tool to overhang the front of the H and heavy > cuts lift the right of it a thou or 2.
What some of those 7x Chinese lathes need (especially the early ones) is the bed mounted upside down on a big mill and the bottom outer edges of the ways cut parallel to the top. I used to own Grizzly 7x10 (actually 8" chuck face to tailstock) serial number 346 and it was a POS from the factory. At least three prior owners had abused it attempting to make it work instead of doing what was needed to fix it. There was some crud between the headstock and bed and a spot on the bottom edge of the headstock had been dinged. Cleaning it up and filing the raised ding edge got the spindle square with the bed. Where the rack and leadscrew mounted to the side was mostly "supported" by a coating of plastic filler. I put it on my Harbor Freight 12 speed drill/mill and used a fly cutter to carve all that down to iron. It required a lengthwise shift to cut the full distance, which was achieved with some careful measuring etc to ensure I wouldn't have to move the table in or out. (If I'd had access then to a big mill I would have cut the underside of the bed too. I improved it a lot by scraping with the end of a flat file.) The slide dovetails both had some taper so I used an old Chinese tilting vise to set them up. Only had 30 degree dovetail cutters, thus the need to tilt to cut 45 degrees. Once I was done with it, the lathe was actually pretty decent to use. It could have benefited from a PWM controller upgrade to replace the very simple SCR chopper - which when I got it had a resistor that had overheated to the point where it had come un-soldered. I just hit that with an iron and it was good to go. That was my second lathe. My first was a Homier "Speedway" 7x12 (14" between centers) which was pretty well as perfect as they got out of the box. There's a better grade of 7x, not made by SIEG, which has several better features. The headstock is mounted with 4 instead of 3 bolts, the saddle is rectangular, heavier than the SIEG's H shape, it has way wipers, the apron is thicker and the crank shaft has dual ball bearings. The other major improvement is a leadscrew adjusting nut on the right end with a set screw in its end. The right leadscrew support also has a ball oiler instead of a plain hole. Various companies around the world sold that version, most later switched to the cheaper one from SIEG. My Homier was the better style. I was going to buy another one but by then they'd switched to the SIEG version. Times have changed, and so have Chinese machine tools. 3 years ago, SIEG started building small lathes and mills with brushless DC motors, and adding many more products to their line. http://www.siegind.com/products.html --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ------------------------------------------------------------------------------ Slashdot TV. Videos for Nerds. Stuff that Matters. http://pubads.g.doubleclick.net/gampad/clk?id=160591471&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
