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Re: Saddle/Carriage adjustments
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I remember Ted Hansen's article about correcting the carriage when it appeared in Home Shop Machinist. If the book is the same, I was not impressed.? In the HSM article, Hansen designed an additional gizmo to help the carriage stay straight, but that ignores the real problem. The problem is the original gizmo that's on there -- the spring-loaded device?that holds the carriage down on the minilathe bed. It's a Mickey Mouse design, but it's there for a reason.? The factory didn't machine the underside of the bed, which was left as a rough cast iron surface. This surface didn't have a constant distance from the top surface of the bed, so the spring device compensated for that by pulling the carriage down no matter what the thickness?of the?bed was. But the?real solution isn't to keep this gizmo or to add extra?gizmos, but to get?the underside of the bed parallel to the top side. Then you can? get rid of the spring loaded device and use shims to adjust the keeper plates. I did that decades?ago, and my carriage remains smooth and shake-free, and so stable I haven't needed to adjust the shims in years. Here?(Under the section called "the carriage") is a link to the procedure that I used in 2002, which Frank Hoose conveniently put on his? site:? ?? I'd mostly do it the same now, but there are a few changes I would make: 1. First, I did this on? my?original 2002 bed, which was very bad, but some newer beds are much better and don't require much lapping (or perhaps any lapping). About 5 years ago I replaced my original 10" bed with a 14" bed from LMS, and I was pleased to discover that the underside of the bed was finished pretty well.? But those beds are part of the 14" bed kits that LMS sells. I don't know if the typical beds sold on minilathes are as good as that. 2.? In these directions, I used Mother's Metal Polish, which is extremely fine.? That was tedious and took hours, but I was trying to do it really slowly because I was inventing the procedure as I went along and wanted to be able to catch myself if I was screwing up.? Now this method is fairly well known, and I would recommend valve-grinding compound instead. 3.? Also, I should stress that this is to lap the UNDERSIDE of the lathe bed, NOT the top of the bed, which is precision ground.? The top side should be kept clean and lubricated, but no abrasive should get there at any time. 4. Finally, lapping two things together with abrasive always changes both surfaces, so you're changing the keeper plates also.? You don't want those changed, but this isn't a problem because they can easily be flattened on sandpaper after the lapping is over. Mike Taglieri On Mon, Jan 31, 2022, 10:41 PM Stan Gammons via <buttercup11421=[email protected]> wrote:
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