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Help, top slide re-assembling too tight

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  • Help, top slide re-assembling too tight

    Hey guys,

    A few months ago, I crashed my lathe (Jet GHB1340A) and destroyed the top slide ( the one the tool post bolts too). I ordered a new top slide from E replacement parts ( if they tell you they have it in stock, don't believe it). I built a tool block to use in the interim and it works well, it is much more rigid than the compound (thanks Sir John). I finally got the cross slide from Jet via e replacement parts.

    I have been trying to re-assemble the compound with the new cross slide. It is very tight assembly, way too tight.

    My question is, do I file the gib so that it fits smoothly or work on the dovetail?

    Tim

  • #2
    Rule of thumb. Wreck the cheapest part first. play around with the gib. hell, Just make a new one.

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    • #3
      yeah, that makes sense

      thanks,

      Tim

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      • #4
        What Rustybolt said....
        ----------
        Try to make a living, not a killing. -- Utah Phillips
        Don't believe everything you know. -- Bumper sticker
        Everybody is ignorant, only on different subjects. -- Will Rogers
        There are lots of people who mistake their imagination for their memory. - Josh Billings
        Law of Logical Argument - Anything is possible if you don't know what you are talking about.
        Don't own anything you have to feed or paint. - Hood River Blackie

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        • #5
          Isn't the gib adjustable? Perhaps you can do something to increase the range of adjustment.
          Any products mentioned in my posts have been endorsed by their manufacturer.

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          • #6
            Originally posted by winchman
            Isn't the gib adjustable? Perhaps you can do something to increase the range of adjustment.
            Winchman, yes the gib is adjustable within a fairly narrow range, I don't think I can increase the range of adjustment, but I might be able to file the gib to make it fit within it's range of adjustment.

            Anybody know what a gib is made of?

            Tim

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            • #7
              Should be cast iron.

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              • #8
                Originally posted by macona
                Should be cast iron.
                Makes sense, I don't think CI to CI will have the galling problems that you would have if you had similar steels or aluminum rubbing together.

                Tim

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                • #9
                  Too tight is much better than too loose.
                  A bit of fitting is required.
                  Dave

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                  • #10
                    New top-slide and old gib? A bad combination, should have ordered a new gib to be fitted to your machine. Is the old gib perfect flat? Have you checked on a surface plate to be sure it hasn't become banana shaped from age/stress?

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                    • #11
                      Originally posted by macona
                      Should be cast iron.

                      Hmmmm.........

                      I don't recall ever seeing a CI gib. Steel, brass...yes.

                      What type of gib is this? Flat or tapered? Tapered can be kind of tricky to make, flat are simple.

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                      • #12
                        The new parts are not going to just fit and work . You are going to have to scrape them in to fit correctly. Any replacement sliding part for machinery will have to be hand fitted to the specific machine.
                        Every Mans Work Is A Portrait of Him Self
                        http://sites.google.com/site/machinistsite/TWO-BUDDIES
                        http://s178.photobucket.com/user/lan...?sort=3&page=1

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                        • #13
                          Originally posted by Rosco-P
                          New top-slide and old gib? A bad combination, should have ordered a new gib to be fitted to your machine. Is the old gib perfect flat? Have you checked on a surface plate to be sure it hasn't become banana shaped from age/stress?
                          Is that as in Roscoe P Coltrane?

                          You are correct Roscoe, the top slide is new, the gib is old. I do believe that it is CI after looking at it a little closer. I did check it on a surface plate and found it to be a little banana shaped, but not much. The lathe has less than a hundred hours on it and the original scraping marks show no wear to speak of. It is a tapered gib, tapering .049" over 6"

                          Since I have no experience with scraping, I think what I will do is sand one side down using a granite flat as a backing plate until it fits snugly ( as in finger tight) at it's loosest adjusting point. That should leave me some adjustment for wear.

                          If I screw it up, I can always buy a new gib

                          Tim

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                          • #14
                            Originally posted by DR
                            Hmmmm.........

                            I don't recall ever seeing a CI gib. Steel, brass...yes.

                            What type of gib is this? Flat or tapered? Tapered can be kind of tricky to make, flat are simple.
                            The ones in my 10EE are cast iron. Heard stories of broken gibs in mills? They are cast iron too. Cast iron is used because it has one of the lowest coefficients of frictions of a metal. Way lower than steel and brass.

                            They may be cast iron and you never know it since if it was made from a piece of durabar you will never know until you try an break it.

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                            • #15
                              Though I'm in general agreement with the gib thing, I would have suggested first to find out why it's tight. If you know it's the gib, great, you know what area to work on.

                              Here's something I've found a couple of times- dovetail surfaces that aren't completely flat. During the machining, a bit of a burr might be raised on one edge. You can do a test and simultaneous cure with a file. Holding the file flat to a mating surface, give it one or two strokes. If it skates across easily, there probably is no burr, but sometimes you'll feel it catch on something. You can play with gibs all you want, but if anything is preventing mating surfaces from having good area contact, you're probably just going to screw up the gib.

                              One I haven't seen, but is possible, is that the mating parts aren't machined perfectly. One or both parts may have a slight twist. I would do a careful cleaning, oil lightly and wipe clean, then check for any rocking. Once the fitup is good, then play with the gib.
                              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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