Once the magic smoke comes out, things don't work any more.
John Kasunich
jmkasunich@fastmail.fm
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Sun, 17 Dec 2006
I started to put the machine at least partway back together this morning. But when I got the saddle on the ways and adjusted the gib, I noticed that it tightens up at at the tailstock end of the bed. This could partly be from wear, since the saddle never normally goes that far down the bed, but I seem to recall the same thing ever since the machine was new. I've learned a few things since then, so I decided to try to fix the problem.
Out came the precision level, the scraper, the Dykem Hi-Spot Blue, and the surface plate. First I leveled the machine both ways, then checked the flat tops of the dovetail ways every inch or so with the level. That indicated a very subtle dip in the center of the back way. Then I blued up the surface plate, lifted it up, flipped it over, and set it on the ways. Slid it around a bit, and removed it. Sure enough, the back way is low in the center, and high at the tailstock end.
I won't bore you with the details, except to mention that lifting, flipping, and otherwise manhandling an 85 lb surface plate is not this desk jockey's idea of fun. And I had to do it a lot. By late this evening though, I had the top of the ways nice and flat.
I also scraped flat the top of the saddle, where it supports the table. And I very lightly relieved the center of the slides on the top and bottom of the saddle, so that the mating surface is just a tiny bit concave. It makes solid contact at the ends, and very light to no contact in the center. That way the ends can wear a little without the sliding surface going convex and getting wobbly.
Tomorrow I need to either scrape or lap the sliding faces of the gibs. Shoptasks are notorious for having bent gibs. The factory stamps a number in the back after grinding them flat, and the metal flow/stress from stamping makes them bend. Stupid.
Once the gibs are flat, time to install the saddle, adjust the gib, and see if anything has changed. I expect the tightness to still be there (but not as bad). After all, I only addressed the tops of the ways, not the angled dovetail faces. Gonna scratch my head a little and figure out how to tell which face needs scraped to relieve the tight spot while keeping everything straight.
(posted: 17 Dec 2006 23:57) (permalink)