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2714Re: Tramming Spec?

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  • gtrz240
    Jun 4, 2002
      --- In mill_drill@y..., Stan Stocker <skstocker@a...> wrote:
      > Hi Duncan;
      >
      > A 10 thou out of the crate variation isn't surprising. You may
      want to
      > clock at several positions around the table, perhaps at 12, 3, 6,
      and 9
      > o'clock. You'll likely find some front to back as well as side to
      side
      > variation. Sweep over the table, there is a slight low spot of
      about 2
      > tenths near one of my T slots. If you end up taking a reading in a
      > hollow you'll be chasing weird numbers all night! I write down the
      > numbers, selecting the lowest point, and zeroing the dial of the
      > indicator at that point, with about .1 of total indicator motion.
      This
      > ensures a consistent spring pressure at each reading point. This is
      > assuming you are using a thou reading indicator with 1/2 or more
      inch of
      > travel. If you are using a tenths reading indicator the available
      > travel is much less. I certainly wouldn't recommend a tenths
      reading
      > indicator until you are down to not more than 1 1/2 thou total
      variation
      > in any case.
      >
      > Clean the table with carburetor or brake cleaner before indicating,
      an
      > oil film can vary by over a thou. Buff the surface with a lint free
      > cloth, lint from a paper towel tends to give 2 thou worth of false
      > reading. If you rezero at the same point after each loosen, insert
      > shim(s), snug up cycle, you'll be able to tell quickly if you're
      getting
      > things better or not, or if you are making one axis worse before you
      > waste too much time.
      >
      > Depending on your patience, you can get to within a thou over 12
      > inches. Getting it down to a few thou total variation is certainly
      > worth the time, how far you go past that is just a matter of tweak
      and
      > test. Figure on a few hours the first time you do this, taking a
      break
      > now and then to avoid a sore back and head :-) The last thou may
      well
      > take an hour to chase. Make sure your gibs are adjusted correctly
      > before you start or the table may sag slightly. If you have a large
      > domed button tip for your indicator you'll save lots of time
      lifting the
      > tip clear of the T slots. Vacuum off all of the body filler crumbs
      > before cracking the bolts loose, a crumb of bondo under a shim will
      > drive you nuts as it powders a bit more with each snugging. I
      missed a
      > little bit and wasted around 1/2 an hour before I realized what had
      > happened. Try to snug the bolts evenly and to the same tension each
      > time, using a torque wrench wouldn't be unreasonable if you have one
      > handy.
      >
      > If you need a shim a tad thinner than 1 thou, rolling papers
      (cigarette
      > papers) are one thou thick, and will squeeze down to about 9
      tenths. I
      > guess you have to play some old Doobie Brothers if you use papers :-
      )
      > Always fun watching the local quicky store clerks faces when my
      going
      > grey self grabs 2 or 3 packs of Easy Widers! Rolling papers are
      handy
      > for quick edge finding too, just oil a rolling paper on the side of
      the
      > work and creep the spinning cutter in. When it justs snicks the
      paper,
      > you're 1 thou from the edge.
      >
      > Cheers,
      > Stan

      Hi Stan,
      I just purchased a used Jet JMD18 mill drill and would like to know
      more about tramming. Where to I install shims and where do I put the
      dial indicator? Sorry but I'm really new to this machining thing so
      any info would be great! Any other tips on what to buy for it as far
      as tooling? The machine is 6 years old and came with a Shooting Star
      two x,y, dro and a enco power table feed. Looks like it had lite use.
      I can also purchase a Jet rotary table and index table for another
      $200 from the guy I bought the mill/drill from, should I get them
      too?

      Thanks, Dan
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