Grinding removable Leblond lathe ways - Page 3
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  1. #41
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    My only experance with regrinding bolt on ways was with a BPT 412 machining center that spent all it's life cutting Invar. Way's were deeply scored, about 0.005 or so. Turcite needed replacing to but that was easy. Talked at lenght to the engineers at the factory in England and was nervous about doing this. Removed the saddle and used a 1/4 inch chissle to dig out the mogilise in all 10 SHCS holding the rails down. Put the rails on a Bloom?, you know, German made surfice grinder and cleaned them up with minimal grinding. Did it myself. The bolts were in a staggered patteren. One on the left and one on the right, all 10 of them on each rail. Had to refill the boltheads again and scrape them down, you know the procedure.
    Put it back together with bluing to catch the pattern and geometry and the rails were all cattywompest. Twisted back and forth at each hole or bolt. Only about a few tenth's but I was not happy. Rescraped the sadle and let it go.
    I have no problem with bolt on hardened steel ways on a machine but they should never be unbolted in my opinion unless you know the factory procedure and I talked at lenght to the engineers that design it. I was told that I would be up against a brick wall, trying to shove a wet noodle up a snakes ass and should have taken the advice I was offered but I wanted to save the machine. It did produce good parts untill they went out of busness so it was a little of a success but I was not happy with it. Just my opinion.
    Bill

  2. #42
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    At Cincinnati the guys would build skin mills. These were milling machines on steroids. Multibles of fifty foot bed sections laid end to end and also side by side. Tables would be sixteen foot wide and hundreds of feet long. These ways were bolted on. After they were bolted, the guys would have injection sites and they would have a water thin concoction that had to be mixed and then it ran in between any air gap between the ways and bed. You had to know what you were doing by way of modeling clay dams and such. If the stuff found a way out, out it would go. After a period of time it would become rock hard. Weird stuff

  3. #43
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    Oh! you are going to see every screw. I don't care how fierce and frightning you make your ways. Our Giddings&Lewis hbm's had four inch thick and six inch wide (This is from memory, but thick and heavy nonetheless) Ways on them and the surfaces were scraped underneath. I don't know what they made them out of but they were as hard as Chinese arithmetic. Under neath the protected surfaces of the saddle and carriers were covered with reulon. Sort of a fancy red turcite. These machines were remarkably accurate workhorses and I was involved in reworking several of them. You could look down the ways and see every bolt area. The ways would actually look scalloped. Wouldn't affect a thing. After awhile you just quit looking at the funny pattern. Other than visually noticable I guess the microfine dips formed oil wells.

  4. #44
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    chevy43:

    This is the math I used to regrind my LeBlond ways. Mind you, this is not a recommendation, as my lathe is not yet back together and properly working. It's just documenting the process. If anyone wants to challange my math, please do so. This method made sense to me. The goal here is to regrind the ways so that the carriage (and half nut centerline) drop only in the vertical plane. The quick change box and rear leadscrew support must also drop in the vertical plane an equal amount.

    If you stand at the end of the front way by the tail end leg, looking toward the headstock:

    For each .0010" stock removed from the "short" edge of the front way the carriage will drop .000342" vertical AND move AWAY from the spindle centerline .000939"

    For each .0010 stock removed from the "long" edge of the front way the carriage will drop .000939" vertical AND move TOWARDS the spindle centerline .000342"

    So... a little stock removed from the "short" edge moves the carriage away from the spindle centerline "almost" an equal amount with a small vertical drop. However, a little stock removed from the "long" edge moves the carriage back towards the spindle centerline only a little, while the vertical drop is "almost" equal. This means that more material must be removed from the "long" edge of the way (by a factor of 2.7473 or .00093969/.00034202)for the carriage to drop only in the vertical plane. (Sorry about all the decimal places; I did this on AutoCAD.)

    Your thinking is correct in that an amount equal to this total vertical drop must be removed from the "long" edge of the rear way (and from the vertical location surfaces of the quick change box and rear leadscrew support bracket.)

    Keep in mind that a cast iron carriage has been sliding on a 62-64Rc way surface for years, so the carriage has already dropped and moved a bit (away from the spindle centerline, I would guess.) Rescraping will move the carriage a bit more, so you might "intuitively" allow for this.

    Be mindful that the leadscrew/half nut centerlines are not in "dead nuts" alignment with the front way. From Connely's MTR book, which mirrors the NMTBA tool room lathe standards of that era: 0 to .004" parallel with ways horizontal and vertical for the leadscrew and 0 to .006" alignment of half nut horizontal and vertical. A large swing lathe such as yours allows more deviation in these alignments.

    Mike

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    TomPracMac I would only mount those ways on the machined surface of the bed. If you try and raise them up they will no longer be alinged by the bed and whatever twist or bows they have your lathe will have for ever more. That would be my fear anyway.

    Mike, Thank you for your exelent response!

    Treven.

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    I read a piece about a machinist who had a precision job to do and the only lathe at his disposal was one with the ways and leadscrew pretty well worn out near the headstock end. He chucked and trued up a piece of barstock in a four jaw and roller steady rest and machined the end of the bar stock to replicate the end of the spindle on the machine. He then installed another chuck on the newly machined spindle extension, and performed the close tolerance work at hand on the unworn portion of the ways and leadscrew.

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    Lathefan, I'm glad to hear about that. I've contemplated that idea more than once but never have done it.

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    Hmm!

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    traytopjohhny,

    Can you please explain what a skin mill is? It sounds like something you could place a wing on, or...??
    Not something I have ever heard of.
    Good reading your (and others) comments so far.

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    A skin mill was exactly that. We made a lot of machines for the aircraft industry. The skin mills profilers etc had sectional beds and could theoretically been made as long as desired. I was never involved in the assembly of the product Milacron produced. I repaired, rebuilt, aligned, installed, moved, adjusted and cussed at the equiptment Milacron owned to produce the parts. The aviation profilers, skin mills, etc some times had multiple heads that would move in unison making as many parts simultaneously as the machine had heads. Some machines were sometimes five axis and huge. We worked for any major aircraft manufacture. Boeing knew who we were as well as airbus. We made a machine that unrolled a bunch of tape and made Stealth bombers. It was pretty neat. We made special purpose machines. Spar mills etc. Actually, everything we made was probably special order and for an intent purpose.

  11. #51
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    A rather small machine we made but one of the slickest I can remember was a drilling and tapping machine that once you installed the tracks in an airplane that would hold the seats you would plop this thing down on the floor and it would automatically drill tap cobore cosink whatever it took all the holes on an aircraft floor. There are a lot of holes on the floor of anairliner.

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    I thought I'd chime in after TTJ on the skin mills.

    I have a Cincinnati Milacron Profiler sales brochure from 1982. It has some great photos of these huge skin mills. I'll try to scan a few pages and post them a bit later.

    TTJ & I have always lived in a world which was full of new and special, state of the art machine tools. We saw these everyday without realizing that what was commonplace for us was very unique to others.

    Mike

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    Those skin mills have been all over the Los Angles area scrap yards in the last few years. Boening etc dumped most of them for newer CNC and also the air craft industy is dying or dead in So.Ca.I was at one place a few years ago and looked at one. The owner asked if I was intrested. I said maybe and he said I could have it for free. It had about 3 50 taper heads on it. It was too big for me to take home. I'm sure they are all in the Ying Shee ( or whatever it is called ) dam in China by now.

  14. #54
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    Treven....give me an e-mail, if you would, please, on '[email protected]'

    (I lost all my e-mail files with the e-mail addresses when our computer malfunctioned recently)

    cheers

    Carla

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    I wouldn't be surprised if skin mills wern't being scrapped. If you used to build airplanes and it is no longer fashionable to fly, the skin mills would be in the way of the next renter of the building you are in where he wants to open up a laser tag operation or maybe even an indoor driving range. Maybe even an indoor 9 hole golf course.

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    Chevy43 Just curious. Was this machine in one piece? Most skin mills would probably need eight or ten ten trucks if not more just to move. You are not perhaps mistaking a Hydrotel for a skin mill? Is this a possibility. You would need a building with a fancy crane just to erect it. I'd be scared to think of the foundation. A fortune many times over just for the concrete and rebar.

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    Chevy43, I agree with your concern and advice about the problems and dangers of trying to shim the re-ground ways back up to their original position.

    The suspension points ( ... step n) in my post
    indicated I left out the hard parts:
    (1) Devising a yet-to-be-devised method for modifying the bed, or removable ways, or the hold-down bolts or some combination thereof to permit positioning re-ground ways in their original horizontal positions, and
    (2) Devising a yet-to-be-devised gage for positioning the front way very accurately in its original horizontal plane.

    If I come up with something worth sharing, I'll post it. And if I ruin things, I'll confess.

  18. #58
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    Just sittin here after work doodling on the cad system and I got to wondering how much material removed from where did what on a Leblond regal front way. I drew it up, (hey it's been a long day and I'm too tired to go find my calculator lol), and to keep the front way in the same location as original, compared to the spindle centerline, just moving it straight down, it takes .0009 off the 20 deg top face and .0003 off the other smaller face to move the carriage down .001".

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    I have really enjoyed reading this thread as I have just bought a nice 15" Dual Drive and have learned a lot from you fellows with so much experience. Thanks!!
    Michael

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    I seem to recall an article I saw years ago where the ways were air hardening steel that was hung by one end and induction heated, Honeywell bought a new 16" LeBlond and the handbook might have had that information.


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