| Gallery, Projects and General > Project Logs |
| Building a New Lathe |
| << < (34/171) > >> |
| vtsteam:
I attached the new 600 line encoder to the toy motor and ran 375 rpm. The FORTH code handled the data rate fine all the way through 6TPI pitch - the coarsest I plan on. And likely requiring lower spindle speeds anyway, as it's usually found on larger diameter work. However the stepper motor started to miss step at that spindle speed. Finer pitches worked fine. It's a 20 year old used stepper. Not the motor that will go in the lathe. And I was only running 12 volts. I can run 24 v and that will allow higher step rates. So it does look like the high resolution encoder won't outrun the board. And the electronic leadscrew has a good chance of working out. |
| vtsteam:
Spent part of today scraping the edges of the bed ways . I finished the back outer edge and am using it now as a reference to scrape the front edge. After that is done, I'll work on the two inner edges. Some things I learned long ago in woodworking are very useful while scraping an edge parallel with another. To correct a tapered board with a joiner, you drop the narrow end down onto the bed just past the cutter head, so a bit of uncut edge rests on the stationary table. This cuts progressively deeper at the wide end of the board. When parallel, you then take a full pass to remove the slight bump. While scraping I realized that to bring an edge parallel to another edge you want to concentrate your scraping at the high spots closer to the wide end (if the high spots haven't fully reached either end). And leave the unscraped high area near the narrow end to support the straightedge. (Just like the stationary table on a joiner) . Which seems anti-intuitive. The tendency is to want to scrape all the high spots off full length. The edge will then end up straight, but it will not be parallel, and you will eventually have to scrape to bring it in. Instead, take off metal only near the wide end, and leave high spots near the narrow end untouched even though the narrow end hasn't been reached with marks. This will force the marking progressively down the wide end. Once the scraped portion is parallel by measurement, you can then continue to scrape evenly. all the high spots at both ends to bring the edge flat. Hard to explain, but it does work. Anyway, thought I'd pass that on.... |
| rowbare:
In one of the scraping DVDs I have (I think it is Richard King's) he describes scraping by zones to get rid of a taper. For example if you know that you usually remove about a tenth per pass and you are 1 thou high, divide the length into 10 zones. Starting from the high end, scrape the first zone. For the next pass scrape the first and second zones, for the third pass scrape the first, second and third zones and so on. Then once you have your alignment you finish scrape for flatness and bearing. bob |
| vtsteam:
I think I might have seen that video years ago, Bob. Did it have a segment at the end showing the casting of straightedges? Anyway, that method would work, too. I do kinda like mine -- it only takes occasional measuring, and no special marking. They both finish up the same way once parallel is reached. I also want to reiterate from the scraping yesterday (with my tools) that on narrow work, one filing is worth ten scrapings, and if anything is more than a thousandth off I can cut down hours of work by grabbing a handle-less coarse file, laying it flat and going at the high spots until I reach a thousandth or so rough tolerance. Nothing wrong with files! |
| vtsteam:
I've finished scraping 3 of the 4 way edges today and the fourth is about half way done. Just a progress update. It will be nice to switch to pattern making and casting shortly. |
| Navigation |
| Message Index |
| Next page |
| Previous page |