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SB Heavy 10 Mystery

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  • SB Heavy 10 Mystery

    While cleaning up the SB Heavy 10L that Fred gave my, I've encountered something puzzling. This is a 1963 vintage machine that spent most of its life in an old line job shop in Modesto. Fred said it was their "good machine". Here's the mystery. The cross-feed has, after tightening the nut, .040 lash (.080 on the dial) with no indication of wear on the screw. The ways, however, are PERFECT, no visible signs of wear at all.



    The black line on the way at the left is the forward most edge of the carriage travel. With the exception of a couple of small dings in the area of the chuck, I can detect no signs of wear. These are not hardened ways, at least there is no label indicating such and no sign of there having been one. Without leveling the lathe (extremely rough and irregular concrete floor, the lathe rocks about 1/4 in.), I measure less than .003 drop on the carriage from tail to head.

    I'm truly thankful that it's not the other way around, the cross-feed nut is a cheap, easy fix.

    Can anyone suggest a job-shop scenario where the cross-feed nut got this much wear and the ways suffered none? I'm certain that the ways were not re-ground.
    It's all mind over matter.
    If you don't mind, it don't matter.

  • #2
    It's probably a missing spacer between the screw and the housing , or a worn collar.
    That will give a lot of slop , sometimes on a tight screw assembly

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    • #3
      Like 754 said, the leadscrew often has a something that is effectively a thrust washer.

      But it occurs to me that the play may be between the nut and leadscrew or the leadscrew and the cross slide. Have you figured out which one it is?


      Dan
      At the end of the project, there is a profound difference between spare parts and extra parts.

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      • #4
        It could just be that the ways got more lube than the leadscrew, is there an easy way to get oil on the leadscrew.

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        • #5
          While it is not enough to cause any concern, I do see what appears to be wear on the ways.

          Quite often a large portion of the backlash in the crossfeed is attributable to slop in the feed screw handwheel assembly, not wear in the feed screw or nut. This can be adjusted out or removed by shimming the assembly. It has been a while since I have had one of these apart, but disassembly and cleaning should reveal the procedure. This should be done prior to replacement of parts, as backlash in the feed screw is inevitable and easily dealt with in most cases.
          Jim H.

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          • #6
            As JC says there appears to be a fair amount of wear on the ways. The scraping is all gone, isn't it?

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            • #7
              My SB heavy 10 is a 1953. It came out of the RCA Sarnoff Labs where it was installed in a lab not in their big machine shop. So it is about as pristine as any lathe I have ever seen. They had 3 for sale at a sealed bid auction. Had I known I could have gotten all 3 for the $500 I paid for this one I’d have bid on them all!

              One thing about V ways on a lathe. They remain straight on the horizontal plane as they wear and the tool drops a bit but the effect on diameter when cutting is very small.

              Comment


              • #8
                Originally posted by garyhlucas View Post
                ....
                One thing about V ways on a lathe. They remain straight on the horizontal plane as they wear and the tool drops a bit but the effect on diameter when cutting is very small.
                As long as both wear the same. If the front one wears more, which is reasonable to have happen, it tilts the cutter away from the work where the wear is, which can be much more significant.
                1601

                Keep eye on ball.
                Hashim Khan

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                • #9
                  That machine almost certainly has a hardened bed. I have a 1960 10L with hard bed, no tag, and no frosting on the bed ways.

                  Regarding the cross feed- as has been said, most SB's suffer from poor thrust bearing surfaces in the handle, in addition to screw and nut wear. You can see a gap open up behind the dial, and a feeler gauge can tell you how much of your lash is from that gap.

                  allan

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                  • #10
                    Exactly, grab it firmly pull and push and look for a gap..

                    Comment


                    • #11
                      Those are not wear in that picture, I believe they may be lines of oil from the wipers. It's hard to get a good picture, here's a little better one.



                      I believe I can feel a little wear with my fingernail, but it's very minimal. No flaking/scraping on these ways anywhere, it would appear that they may be hardened even though not marked.

                      Originally posted by danlb View Post
                      Like 754 said, the leadscrew often has a something that is effectively a thrust washer.

                      But it occurs to me that the play may be between the nut and leadscrew or the leadscrew and the cross slide. Have you figured out which one it is?
                      Dan
                      Ding, ding, ding.... No more calls please, we have a winner!
                      I was watching the screw for signs and noticed some movement at the back end thrust bearing, behind the taper attachment. I put an indicator on the end of the screw and, lo and behold, there's the missing .040! I'm going to adjust it, but I feel some "lumpiness" in the screw, like the thrust bearing(s) may need attention.

                      Thanks to everyone for playing.
                      It's all mind over matter.
                      If you don't mind, it don't matter.

                      Comment


                      • #12
                        It sure bears mentioning, Always check that when buying a lathe.
                        If you know it's a spacer, its a fairly easy fix, but you can say, I am not happy with all this slop in the crosslide..

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                        • #13
                          Originally posted by MrWhoopee View Post
                          Ding, ding, ding.... No more calls please, we have a winner!
                          I was watching the screw for signs and noticed some movement at the back end thrust bearing, behind the taper attachment. I put an indicator on the end of the screw and, lo and behold, there's the missing .040!
                          I had the same problem. There is no real adjustment there. When I removed the lead screw I found there is an integral thrust ring on the screw that was worn into a cone shape. I chucked it up in another lathe a faced it square again. I took enough off that I could add an off the shelf oillite thrust washer.
                          I had to measure carefully so I had just enough axial clearance that everything turned smoothly. I did this almost 20 years ago and the backlash is still below .005 inches today.

                          Comment


                          • #14
                            Ah, did you say it had a taper attachment originally? The 10L has a telescoping cross feed screw in that case- all the thrust is taken up by the two bearings in the rear half, either side of the tube the taper attachment clamps. Fortunately, this mechanism is sometimes adjustable- tighten the nut on the back end of the screw, unless it is up against the shoulder already.

                            allan

                            Comment


                            • #15
                              A strange thing.... most SB I have seen have a small flat on top of the v way. That one looks as if it is actually pointed, no flat.

                              Suggests it was re-ground, and is not original. That could be good, or not as good, depending.
                              1601

                              Keep eye on ball.
                              Hashim Khan

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