Announcement

Collapse
No announcement yet.

Atlas Shaper Gib Issues

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Atlas Shaper Gib Issues

    I recently picked up an Atlas 7B shaper at an auction. It seemed to be in reasonable condition, and the price was right. It looks like it sat covered with oil and dried coolant in a wood shop for many years.

    I've been dismantling it for cleaning, oiling, and damage assessment, and just came across the first real problems.
    First, the non-repairable damage. Someone decided a lock screw was a good idea for the clapper dovetail, and they apparently drilled and tapped a hole on the side opposite the gib that was lined right up with the dovetail. They took the corner off the non-gib dovetail. Oddly, the matching dovetail doesn't seem to be badly damaged. I think I'll be OK leaving this alone for now.




    The real problem is the gib. It is bent and damaged in a way I can only call abuse.


    It is also badly bent.


    It appears that the gib is made of a relatively soft steel, based on the lack of damage to the dovetail and the displacement of metal on the gib. I don't have access to a surface grinder, so I don't have any way to make a proper ground gib. Looking at McMaster-Carr, I can get either 4140 prehard at C25 hardness, or a low carbon tight tolerance bar that sounds like A36.

    The machining isn't too difficult from a fixturing point of view, and I do have carbide end mills, but my mill is pretty wimpy(G0704).

    Is there a downside that I'm missing if I use the low carbon steel? Based on what I see of the existing gib, Atlas looks to have used low carbon steel anyway.

    Looking forward to advice from the community.

  • #2
    Regular low carbon should be fine. I have even made gibs out of brass.

    Super smooth ground finish is not necessarily the best. A scraped surface would be the best, but ground, or a good milled finish, either would be OK. Thickness is not critical either, since the adjusting screws will make that up if not excessive. I normally drill or mill screw pockets, and cut the edges at an angle that allows fitting the gib in place.
    CNC machines only go through the motions.

    Ideas expressed may be mine, or from anyone else in the universe.
    Not responsible for clerical errors. Or those made by lay people either.
    Number formats and units may be chosen at random depending on what day it is.
    I reserve the right to use a number system with any integer base without prior notice.
    Generalizations are understood to be "often" true, but not true in every case.

    Comment


    • #3
      I like to make the Gib Plate with ears that stop any movement of the plate. This ensures the "Friction surface is all on one face. AS to material, my preference is Bronze if possible but mild Steel is perfectly good. The choice of bronze is mostly for appearance. Keep in mind that the actual wear surface is a film of oil not the metal to metal contact. If you need some pictures of Gib assemblies I have

      Comment


      • #4
        You might be surprised with an attempt at hand straightening and polishing the gib on paper on a flat surface. Smooth and reasonably flat will work fine, I think.

        Comment


        • #5
          Given the big chew mark I think the bend is the least of your worries.

          OK, I gather that the gib is off the clapper dovetail? If so make it work for the time being even if it's over a limited range of travel. Cut the bent part off if it's the part that has the chewed out divot. You won't need it. Now the fun part. Your first project on your new shaper will be to make a new gib!

          You'll want to make it from some mild steel. Or even better would be some leaded steel so it has a certain measure of self lubrication. The trick will be to hold it. I'm going to suggest that you make it from some 1/4 by something like 2". And you'll form the gib by shaping down from both faces by equal amounts long one edge while holding the rest clamped securely to the table. After the first side flip the stock over for the second side. But not before you shim under the newly machined face to support the metal. Make it a bit wider than you need. After getting the thickness right you should be able to use a couple of custom ground tools to cut the angle on the one free edge. Then measure over with the other cutter and cut straight down with the cutter's face at the proper angle for the other edge. The final cut will present you with a nice new gib. Now mill or Dremel the depressions for the adjuster screws that also locks the strip in place.

          Lot's of good learning and practice and fun with your new machine to be had.

          A trick you might consider is to then stone the rubbing side with a known flat medium stone to flatten the tooling marks if you can't get it ground easily. The idea here is you flatten the peaks and form plateaus that all line up and are flat for better load bearing. And the valleys that are left form oil reservoirs that prevent the oil being rubbed away. Somewhat of the same reason given for ground surfaces being frosted. Just a different way of getting there.

          You COULD mill down the old gib. But then it would be rather thin and that's not a great option either. Within reason the thicker the better.
          Chilliwack BC, Canada

          Comment


          • #6
            If you put in screw pockets, movement will not be an issue.

            Mild steel is fine. You probably do not want to mill it down, because it will warp and give trouble. Plus the finish can be had very smooth ground from the supplier if you get ground plate. If you mill, you will have to mill both sides, which then means you must re-finish one side.

            The thickness is not critical, as long as it fits maybe 2/3 to 3/4 of the space available, at least. No real need to be very precise. And only ONE surface needs to be good enough for a bearing surface. The scrwes will take up the difference, and adjust it to ride correctly on the mating dovetail surface.

            Do the angled surfaces of the edges, then put it in place and use the screws to mark the plate. Drill or mill the pockets for the screws. An end mill makes a good flat pocket, if you have rounded tip, cup, or dog point screws. You make the pockets at the angle of the dovetail, so that the screws hit a flat surface.

            You actually can use non-ground plate for that gib, since it is not going to get a lot of movement. just adjustment, and maybe some advancing if you do angled cuts. Nothing like a lathe crosslide would get, more like the compound.
            CNC machines only go through the motions.

            Ideas expressed may be mine, or from anyone else in the universe.
            Not responsible for clerical errors. Or those made by lay people either.
            Number formats and units may be chosen at random depending on what day it is.
            I reserve the right to use a number system with any integer base without prior notice.
            Generalizations are understood to be "often" true, but not true in every case.

            Comment


            • #7
              Thans to all of you for the information. I wanted to be sure that I wasn't missing something. JTiers, I was thinking about how to transfer the screw pockets and never thought of using the compound screws for marking the pockets. Perfect and simple. The gib is a little over 1/2" wide corner to corner, so I can use 3/4 x 1/8 mild steel flat stock and mill the angles. I think I'll get a long enough piece to make more than one and experiment with scraping oil pockets.

              I haven't torn into the main mechanism of the shaper yet, I've started with cleaning up all the peripheral parts and mechanisms. I'm sure I'll be back with other questions.

              Comment


              • #8
                Seriously, just bend the gib back straight.
                Done all the time.

                -D
                DZER

                Comment


                • #9
                  Originally posted by Doozer View Post
                  Seriously, just bend the gib back straight.
                  Done all the time.

                  -D
                  Except for the other damage I'd agree. When I replaced that sort of gib on my Atlas lathe I used PG stock as I could get it but I suspect decently flat cold rolled would work at least as well.

                  There's a trick to fitting these: get the stock a little wider than needed. Place in the sliding member and 'clamp' into position (I used sliding parallels). Mill the top to get the algle. Flip over with a .010" shim under it with the new edge flat, clamp and mill off close to the work. You now have a gib that's maybe .005" lower in height but otherwise a perfect fit. Mount, pop some holes for the gib screws and go to town.

                  Comment


                  • #10
                    If you go for cold rolled it'll work fine too. And I do like the suggestion for using precision ground tool steel and then just leave it soft. Not as much romance as making it from heavier hot rolled stock but oh well....

                    But if you use cold rolled stock to do the last bit of flattening on the rubbing side I'd at least surface it with some fine sandpaper on a surface as flat as you've got. Surface plate would be perfect. But the table of the shaper itself would work too. It's not like this gib is a super long one after all.

                    A little bluing on the other side before you put the gib in place and run the screws in will aid with making marks that you can see.
                    Chilliwack BC, Canada

                    Comment


                    • #11
                      Wheels17: If you make a new gib, please do your self a favor and make it from cast iron, or as a secondary choice, bronze. NOT STEEL OF ANYKIND. The locking setscrew was for a special application. This was probably done so the clapper would not raise up while cutting an internal keyway. If you will look carefully, your original gib was cast.

                      Sarge41
                      Last edited by sarge41; 12-01-2018, 03:42 PM.

                      Comment


                      • #12
                        Originally posted by sarge41 View Post
                        ... make it from cast iron, ...
                        Check w/ your suppliers to see whether they carry Dura-Bar or other brands of continuous cast iron bar stock in sizes suitable for your needs.

                        Comment


                        • #13
                          There is no particular reason to use CI for the gib. With one side CI and the other steel, it still has the benefit of the CI graphite content.

                          Southbend made tens of thousands of lathes with steel spindles running in CI bearings, and thousands still are around and working without excessive wear. They also used steel gibs on CI dovetails in lathes for decades.

                          Atlas and Logan made several hundred thousand machines with steel gibs sliding on CI. No issues even with crosslides.

                          And your application is a low usage one, far less use than a lathe crosslide. Much less wear or other potential issues.

                          If you WANT TO, go ahead and make it of CI and if it makes you feel better, that's good. But you are not short-changing yourself the other way with steel gibs. There are a huge number of lathes made that way, and they work fine.

                          The CI gib is much more typically made as a fitted taper gib, adjusted not with side screws, but with screws on the ends that move it along the taper to adjust. The superiority of that type is mostly in the fact that it is more securely held, being backed up along the full length, and not just by a few screws at certain spots. It really is not a matter of it being CI. In fact, the CI might not hold up well as a thin gib pushed in by a few screws. CI does not like being bent.
                          CNC machines only go through the motions.

                          Ideas expressed may be mine, or from anyone else in the universe.
                          Not responsible for clerical errors. Or those made by lay people either.
                          Number formats and units may be chosen at random depending on what day it is.
                          I reserve the right to use a number system with any integer base without prior notice.
                          Generalizations are understood to be "often" true, but not true in every case.

                          Comment


                          • #14
                            A few items:

                            I'm pretty sure the gib that's in there is plain low carbon steel, not CI. A quick tap on the grinding wheel gives straight sparks with no showers, which I understand indicates low carbon steel. It's not the conventional taper fitted gib that is used on high quality machines. It's a flat gib adjusted by four dog point side set screws. It's very similar to the gibs on a south bend cross slide and compound. The gib measures a bend of .035 over 2-3 inches. I don't think cast iron would survive that.

                            The hole that created the damage is not related to the clapper lock. That's on the side of the clapper housing and is present. This is down on the dovetail, and has created a mess. It's clearly a hack, and not present on any pictures I've seen of Atlas shapers.

                            I was tied up today, I'm planning to see if I can chase down a local supplier of flat stock tomorrow. If not, I'll have to order.

                            Comment


                            • #15
                              To be fair, the bend in the gib that you describe is not a "feature", but actually a defect of sorts, although not a serious one.

                              But, don't bother with a CI gib, not worth it, and might cause trouble with breakage. Regular CRS is fine, just make one and put it in.... and de-burr that hole...
                              CNC machines only go through the motions.

                              Ideas expressed may be mine, or from anyone else in the universe.
                              Not responsible for clerical errors. Or those made by lay people either.
                              Number formats and units may be chosen at random depending on what day it is.
                              I reserve the right to use a number system with any integer base without prior notice.
                              Generalizations are understood to be "often" true, but not true in every case.

                              Comment

                              Working...
                              X