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  • BOX WAYS

    I was wondering...
    On a machine running on Box Ways;
    What exactly are they?
    What is the bearing surface?
    How are they different than gibs?
    Are they truely more rigid than todays modern linear bearing(truck)type.
    What happens in term of wear on box ways? Once worn are they repairable??
    Thanks for the info guys,
    JD


  • #2
    AFAIK, box ways are basically ways without Vees. My Maximat 7 has box ways, flat topped and square edges.

    In the lathe case, the carriage sits flat on the top of the ways, and the rear "lip" rides on the edge of the rear way. The front of the carriage has a gib which adjusts pressure against the edge of the front way. Just a front to back grip (with other strips to prevent lifting of the carriage, of course).

    added - They are much easier to re-grind since you don't have to deal with the Vee geometry.

    Den

    [This message has been edited by nheng (edited 08-13-2004).]

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    • #3
      Box ways have 90 degree included vees at each of their corners

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      • #4
        I gave some thought to the different types of ways when I was considering making my own lathe and other kinds of special purpose machines. The Vee style ways on the South Bends and a lot of other lathes are perhaps the hardest to produce in the home shop. You almost have to make a casting and then have a machine large enough to mill them. Then scrape them in. I never could come up with a way to make them from standard, available shapes.

        The dovetail is easier to make in that they can be machined from flat stock, although it tends to be large flat stock for decent size machined. Two or three pieces can be bolted together to form the rough shape and then machine it like you would a casting.

        The box style way is easier to do in that a piece of stock can be purchased and all you need to do is scrape it in. Some are purchased as "flat ground stock" and used as is.

        Then there are rod style ways where the moveable parts ride on two round rods. Hereyou just buy drill rods and drill/ream equally spaced holes for them. Lathes and other machines have been made this way. This
        is perhaps the easiest way for a home shop to make ways.

        However, ease of fabrication comes with a price. Rod ways are more fxexible than the other types and it's hard to adjust any slop. Box ways require gibs or adjustments at three places (front or back edge and front and back bottom). Dovetail ways require only one gib and it takes up both vertical and horizontal slack. The Vee ways as used on a lathe are self alighing with gravity and the forces of the machinning and only require front and rear clamps to prevent vibration.

        Another advantage of the Vee ways is not completely apparent at first glance. By using four guiding surfaces instead of the two that the rod, dovetail, or box designs provide you can have more stability in the moving carriage. South Bend and others took advantage of this by placing the headstock, tailstock, and most accessories on the inner two ways and the carriage on the outer pair. This immediately gives the moveable carriage a wider base in the front to rear direction. Then they added extensions to the carriage to wrap around the headstock and tailstock to provide additional length and stability in the left right direction. The result is that the carriage is much more stable and accurate.

        Amazing how smart they were 100+ years ago.

        Back to the original questions, with box ways, essentially the whole surface is the bearing surface. I suspect that certain areas will wear more due to the forces applied but contact is on all four sides with a gap on the bottom for the support structure.

        Paul A.

        [This message has been edited by Paul Alciatore (edited 08-14-2004).]
        Paul A.

        Make it fit.
        You can't win and there is a penalty for trying!

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