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2736Re: Tramming Spec?

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  • ballendo
    Jun 6, 2002
      Hello,

      Stan mentioned something a bit earlier in this thread that I'd like
      to endorse. That is, checking the table for flatness before trying to
      tram.

      When I check a new mill/drill, first thing after cleaning and
      deburring is to adjust the gibs. Then check the table for flatness
      by "traveling" the surface with a DTI in a fixed position in/on the
      spindle ("reading" the table). I take readings every 1/2 inch or so
      and use graph paper to "map" the table (putting a +1 or -3, or
      whatever in each square; using as many squares as necessary to
      represent the whole table. Then this topographical representation can
      have "contour lines" drawn (by looking for patterns of similar +1,-3,
      etc., and connecting the "dots") which can tell you a lot about your
      mill table.

      Now as Stan says, when you go to tram the table, you won't be chasing
      the depressions inherent in your table.

      After tramming, I repeat the process of "mapping" the table, and
      store it(the graph paper) in a binder along with other "pertinent"
      details about that particular tool, such as the readings gotten when
      checking the leadscrews for errors, and the REAL downfeed travel.
      This info can be VERY useful when you are trying to make something a
      bit more precise than usual. Worth the time spent, IMO.

      Hope this helps,

      Ballendo

      P.S. I also endorse Stans mention of finding ways to do things
      without purchasing new tools. Mills can be (and have been) accurately
      trammed with a "Z" shaped rod of wire held in the spindle and feeler
      gauges...

      --- In mill_drill@y..., Stan Stocker <skstocker@a...> wrote:
      > Hi Duncan;
      >
      > Glad to be of some help.
      >
      > A DTI is fine, in fact, as you can drag the indicator and it's
      contact
      > point behind the swinging arm and avoid the whole T slot grabbing
      the
      > indicator rod hassle, while avoiding a lot of neck twisting to read
      a
      > dial. The fact that a DTI doesn't indicate true when the arm
      position
      > is changed doesn't matter in this case, you're just characterizing
      the
      > range of difference rather than an absolute from a reference point.
      > You've noticed by now that the shim thickness doesn't seem to map
      > cleanly as some percentage of the indicated reading, so it all comes
      > down to a seat of the pants creep up on the target sort of affair
      > anyhow.
      >
      > Most folks who are just tramming a mill the first time haven't got a
      > DTI, I usually try not to imply the need for yet another tool when I
      > post, it seems everytime you turn around someone is telling you to
      go
      > buy another tool when you are getting started with a new machine.
      You
      > can start thinking that boats or private aircraft might have been a
      > better choice, at least you know your wallet will get emptied by
      those
      > hobbies!
      >
      > Cheers,
      > Stan
      >
      > Duncan wrote (in HTML - you bad, bad boy! This keeps your messages
      from
      > being quotable :-( )
      >
      > Thanks for all the info Stan. I used a lever type DTI that will read
      > down to 0.0005" but not that great an overall
      > distance (0.030"?). Should I use my 1" travel 0.001" reading DI
      instead?
      >
      > Duncan
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