Loading ...
Sorry, an error occurred while loading the content.
 

Re: RF31 gib strip problem

Expand Messages
  • BobSchmoe
    Mario - Thanks for responding. I think I will eventually have to turn a new screw using the drive dog method you mentioned. The new problem (see bottom) will
    Message 1 of 17 , Jul 2, 2002
      Mario -
      Thanks for responding. I think I will eventually have to turn a new
      screw using the drive dog method you mentioned. The new problem (see
      bottom) will probably require a custom screw if it is to last.

      --- In mill_drill@y..., "Mario L Vitale" <mariol.vitale@a...> wrote:
      > Bob,
      > I guess I forgot you mentioned the excess play in the screw
      thread itself. If you have a lathe, it shouldn't be too hard to make
      a new screw with oversized threads to fit the existing female thread

      [... stuff omitted ...]

      locking screw. And guess how they make self locking screws....deform
      the threads!
      >
      Mario







      Paul -

      What model do you have? If possible, can you post some pictures of
      what the front and back adjustment screws look like? I might end up
      retrofitting it like this if my problems continue.


      --- In mill_drill@y..., "Paul Weber" <pbweber@j...> wrote:
      > I went and looked at the table in my machine again. Both ends of
      the table
      > are drilled and tapped. The gib and screw are installed in one end
      and a
      [... stuff omitted ...]
      > Paul.










      Anyway, thanks for the responses you guys gave earlier.

      A few hours ago, I pulled the gib and adjustment screw out and
      apparently the clearance between the head and slot was about 0.035".
      I ended up welding and regrinding the slot. This brought it down
      about 50%. To my dismay, the adjustment screw's head varies in
      thickness about 0.015" from one side to another! Then I flattened
      the screw head a bit... so overall its better, but far from perfect.

      I did a little more digging and found out what the *actual* cause of
      the problem was. I also looked at the other axis which has held up
      very well and does not have any of these problems. Apparently, the
      counterbore that the adjustment screw sits in was bored ~0.050" too
      big. This allows the adjustment screw to wobble radially as the
      table is moved back and forth. With time, this enlarged the threaded
      hole and lead to the excessive play and looseness. This lateral play
      also ended up grinding the gib's slot bigger, causinging to the
      binding that I described in an earlier post.

      I ended up sticking a 0.020" thick shim around the perimeter of the
      bore to take up most of the radial play. What a difference that
      made! The machine is now usable again, but its still not perfect...

      In the meantime, I will probably put some round shims behind the
      screw head to further reduce the slack in the gib's slot (Im tired of
      welding and regrinding). Im also contemplating putting a die spring
      or some belleville washers behind the adjustment screw to preload it
      and keep it from vibrating loose. Im still interested to see what
      Paul Weber's second jam screw looks like though. Eventually, I will
      have to turn an oversized screw to solve all these once and for all.



      DOH! All this because of a manufacturing defect...
    • ballendo
      Bob, Get some tubing the diameter of the head of the gib screw. Slice off a short piece. Turn a shoulder in the head of the gib screw to fit the ID of the
      Message 2 of 17 , Jul 3, 2002
        Bob,

        Get some tubing the diameter of the head of the gib screw. Slice off
        a short piece. Turn a shoulder in the head of the gib screw to fit
        the ID of the tubing. (You mentioned having a lathe; but this can be
        done on the mill with a boring head, holding the screw vertical in a
        vise. Or a hole drilled in a block of material. slice one side
        through to the hole to create a clamping ability. put the boring bar
        in "backwards" and run the spindle in reverse.)

        Assemble with CA, epoxy, silversolder or brazing. Turn the now
        oversize head to fit the slot in the gib.

        The type of spring/device to use behind the gib screw to preload it
        against one flank of the poorly-sized threads will depend on the
        amount of projection of your particular screw. Consider urethane rod
        which can be drilled to fit the screw and parted/sliced to
        appropriate length. Hardware store vinyl tubing can be a simpler
        shorter term fix. Both of these will help in the vibration arena as
        well.

        On that note, what is causing such vibration? Consider making an
        attempt to reduce this at its source, as it is likely affecting more
        than just your gib adjustment...

        Hope this helps,

        Ballendo

        P.S. Be careful of thinking that a replacement gib strip will fit
        well. These machines more than occasionally have parts which
        are "fitted" together as assembly progresses. And by this I don't
        necessarily mean fitted in the makes-it-better way; more like the get-
        it-to-fit way. Speaking of the gib strip: have you tried some
        lipstick or "blue" paste to check its fit? Sometimes a bit of
        judicious filing/stoning can make these machines MUCH better.
      • Gus_935
        Are you sure the locking screw is not missing? ... opposite
        Message 3 of 17 , Jul 3, 2002
          Are you sure the locking screw is not missing?

          --- In mill_drill@y..., "BobSchmoe" <bobschmoe@y...> wrote:
          > Hi Paul,
          >
          > Sorry. There is only 1 screw on the front side and the back of the
          > gib is open to the air.
          >
          >
          > --- In mill_drill@y..., "Paul Weber" <pbweber@j...> wrote:
          > > Does your machine have a stop screw on the end of the gib
          opposite
          > the
          > > adjust screw? My machine has a screw that forces the gib against
          > the
          > > adjustment screw placing a binding force on the adjustment screw
          > so it
          > > cannot move.
          > > Paul Weber
        • BobSchmoe
          Gus - Yeah, Im 100% positive that there is no sign of a locking screw or even threaded hole. I checked the breakout diagram in the back of the manual and
          Message 4 of 17 , Jul 3, 2002
            Gus -
            Yeah, Im 100% positive that there is no sign of a locking screw or
            even threaded hole. I checked the breakout diagram in the back of
            the manual and there is only and adjustment screw in the front. The
            back is plain.

            --- In mill_drill@y..., "Gus_935" <gus_936id@y...> wrote:
            >
            > Are you sure the locking screw is not missing?
            >






            Ballendo -
            Ive upped the shim going around the circumference up to 0.030" and
            put a little bend in the middle of it so that it binds against the
            side of the adjustment screw. The combination of the added support
            and the binding seems to keep the head of the screw completely
            stationary. It also seems to resist vibration fairly well, so Im
            going to hold off on the die spring until later.

            As for a replacement gib strip -- thats actually one reason I decided
            to weld and grind the existing one rather than order a new one. I
            didnt want to gamble with the new gib having the correct taper.

            I also should eventually get some bearing blue and polish the ways a
            bit. The machine has been in service for a long time now and it gets
            a little loose in the middle of its travel.

            In terms of the vibration, I usually do all I can to reduce it...
            but in this case I can't. Im machining 7075 with a 3/4" roughing end
            mill which has saved me many hours of milling. Also, the vibration
            it causes isnt *that* bad. Its just that the adjustment screw had so
            much play that even slight vibration would cause it to rattle loose.
            Coupled with the extra lateral motion caused by the gib going back
            and forth, the damned screw used to turn 2-3 turns in an hour!



            --- In mill_drill@y..., "ballendo" <ballendo@y...> wrote:
            > Bob,
            >
            > Get some tubing the diameter of the head of the gib screw. Slice
            off
            > a short piece. Turn a shoulder in the head of the gib screw to fit
            > the ID of the tubing. (You mentioned having a lathe; but this can
            be
            [... stuff omitted...]
            > The type of spring/device to use behind the gib screw to preload it
            > against one flank of the poorly-sized threads will depend on the
            > amount of projection of your particular screw. Consider urethane
            rod
            [... stuff omitted...]
            >
            > On that note, what is causing such vibration? Consider making an
            > attempt to reduce this at its source, as it is likely affecting
            more
            > than just your gib adjustment...
            >
            > Hope this helps,
            >
            > Ballendo
            >
            > P.S. Be careful of thinking that a replacement gib strip will fit
            > well. These machines more than occasionally have parts which
            [... stuff omitted...]
            > lipstick or "blue" paste to check its fit? Sometimes a bit of
            > judicious filing/stoning can make these machines MUCH better.








            Anyway, it seems to be holding now. I will probably have to make an
            oversized adjustment screw in the coming months depending on how long
            the current fix lasts.

            Im still interested in seeing pics of what the locking screw on the
            backside looks like. This might be very useful because this should
            keep the gib totally stationary and end the annoying change in
            tension as you go forward and back.
          • Country Bubba
            Just to jump in, Mine only has one screw and no place for the second. I have been thinking of trying to add a second for the same reason. I have a Rong Fu 31
            Message 5 of 17 , Jul 3, 2002
              Just to jump in,
              Mine only has one screw and no place for the second. I have been thinking of trying to add a second for the same reason.

              I have a Rong Fu 31 machine also.
              At 11:31 AM 7/3/02 +0000, you wrote:

              Are you sure the locking screw is not missing?

              --- In mill_drill@y..., "BobSchmoe" <bobschmoe@y...> wrote:
              > Hi Paul,
              >
              > Sorry.  There is only 1 screw on the front side and the back of the
              > gib is open to the air.
              >
              >
              > --- In mill_drill@y..., "Paul Weber" <pbweber@j...> wrote:
              > > Does your machine have a stop screw on the end of the gib
              opposite
              > the
              > > adjust screw?  My machine has a screw that forces the gib against
              > the
              > > adjustment screw placing  a binding force on the adjustment screw
              > so it
              > > cannot move.
              > > Paul Weber

              Bubba

              OLDER THAN DIRT
              Country Bubba
              (Actually the inventor of Country and Bubba)

              axtein@...
              LaGrange, GA

            Your message has been successfully submitted and would be delivered to recipients shortly.