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Bed Grind-Harrison Lathe
- Thread starter Madpiper
- Start date
HI maybe connect with @RobinHood he might have some info on that as I know he has a similar situation with one of his lathes..
Perfect application for scraping. It is very difficult to grind V way geometry to be exactly the same so it mates existing geometry. The usual process to make a lathe, at least back when the fit mattered lol...... was to grind the bed then scrape the components to fit the bed. Also why when redoing a lathe that after regrinding a bed, everything is scraped to mate with it.
It would not be difficult to scrape it to perfection, as good or better than grinding, however, if not yet set up there's a bit of leaning curve and tools to collect.
It would not be difficult to scrape it to perfection, as good or better than grinding, however, if not yet set up there's a bit of leaning curve and tools to collect.
Chipper5783
Super User
Have you measured it? Put some straight edges along (even just a quality scale). Is it way off? Is it sitting high (have to remove material)? Maybe it just needs to be shimmed up? Where are you in Alberta?
First questions I’d ask is hardened bed or soft? Are there dowels/taper pins to hold gap piece in place accurately? Is the gap high compared with bed? To me these (and budget/time available) would answer question of grind vs scrape. Or just move on to another lathe. Even if the answer is grind I’d want to scrape the bottom of gap and mating surface of bed to good match before grinding.
Yes, the gap piece on my CMT URSUS 250 is missing. The gap is 10” wide. I am in the process (very, very slow process) of making a new one.
I plan on “building it up from parts” kind of like a LEGO set. The base and side walls will probably be of welded construction (base scraped after manufacture to fit bed).
The way surfaces will be machined and surface ground separately. If I get the geometry right, I might not have to scrape them - if not, I will. Then I will come up with a way to mechanically combine the base with the way pieces. I am thinking keyed & or pinned with bolts to hold it all together.
Max Grant (Swan Valley Machine Shop), is devising some fixture to mount a grinding wheel on so that he can regrind the ways on one of his lathes. If it works out for him, I might go down that route.
The URSUS has a massively wide saddle and even without the gap piece in, there is little overhang into the gap when using any chuck. I want the gap piece for faceplate and collet work (where the saddle is much closer to the HS).
I plan on “building it up from parts” kind of like a LEGO set. The base and side walls will probably be of welded construction (base scraped after manufacture to fit bed).
The way surfaces will be machined and surface ground separately. If I get the geometry right, I might not have to scrape them - if not, I will. Then I will come up with a way to mechanically combine the base with the way pieces. I am thinking keyed & or pinned with bolts to hold it all together.
Max Grant (Swan Valley Machine Shop), is devising some fixture to mount a grinding wheel on so that he can regrind the ways on one of his lathes. If it works out for him, I might go down that route.
The URSUS has a massively wide saddle and even without the gap piece in, there is little overhang into the gap when using any chuck. I want the gap piece for faceplate and collet work (where the saddle is much closer to the HS).