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Extension bed for an Atlas 681

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  • Extension bed for an Atlas 681

    Hello, As I've said before, I have a Atlas 618 in good condition. Over the years, I've managed to accumulate most of the accessories available and all of the accessories that I need. The little lathe suits me.
    There are times, though when it would be nice to be able to work longer pieces. As it happens, I have a spare bed which I sometimes consider cutting down (I don't need 54" between centers!) and, for lack of a better term, splicing on to the existing bed. I believe I've solved most of the problems (at least in theory), i.e., extending the lead screw, leveling the beds, mounting the whole thing on a steel plate, etc. But the thing that stymies me is the rack. How could one seamlessly extend the rack onto the extension bed? Have any of you ever done such a thing; and if so, how? Do any of your have any ideas? I fully expect to have have opened myself up to all sorts of snide comments about get a bigger lathe or get a SB or Sheldon or whatever. But I hope that some of you may be sympathetic and helpful. Thanks to all of you who choose to respond.

    Cheers,
    John

  • #2
    If "you don't need 54" between centers", and thus presumably the extra bed IS 54"..................

    I was not aware that the 6" ever was made in such a length, though, and if it is for a different unit, how would you graft it on????... But taking it as a given that it would work (which I do NOT know. and kinda doubt)............

    Why not swap the parts over to the 54" bed and "put up with" the extra length?

    Seems better than destroying a good long bed to add a somewhat effective extension onto a shorter one.......
    1601

    Keep eye on ball.
    Hashim Khan

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    • #3
      Atlas sold a bed extension for the 618, mainly for woodworking. I could never figure how you could get the thing aligned well enough for anything else. Never seen one in the flesh. Need more bed length? Get the real thing.

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      • #4
        Hi John,
        I take it with the 54 inch bit you meant that joining the 2 at standard length beds would give you 54 inch, which you don't need.

        I am not familiar with the Atlas, but after having a look on lathes UK I see they are just a flat bed. You could join the 2 and shim it to get them aligned, but you would have to check the dimensions of both beds to see if they will line up in width for the tail stock and carriage as you will need them to be the same for accuracy and alignment as it passes from one to the other.

        If they do match up in width and you go ahead with it, I would use a long rigid bar attached to the carriage with a dial indicator on the end, this way you can align the add on bed while the carriage is still on the original bed. Just make sure your gibs are nipped up to stop and rocking giving false readings.

        The rack should not be that hard to match together and I think it will be one of the easier things to do in the conversion. You can just elongate the mounting holes slightly and shim them to height.

        Dave

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        • #5
          54 inches!

          Hello again all, I guess I should have been more explicit. The original Between centers distance on a 618 is, of course, 18inches. The beds are 36 inches (that, needless to say, includes both head and tailstocks). So adding a stripped 36 inch bed to the existing bed would give one about 54 inches between centers. Naturally one could not use the entire stripped bed because of the cutouts for the head stock. I was thinking about having the "spare" bed cut and milled to shorter length at one of the cross piece webs and, probably mounting the original headstock legs under the milled end of the shortened bed.

          Dave, I very much like your idea of a rod with a dial indicator to help in the shimming process. Thank you!

          But I remain puzzled by the rack. It stops quite short of the ends of the lathe, so, to my way of thinking that would effectively prohibit the carriage
          from moving onto the additional length of bed. Now, it, too has a rack but that rack also ends shy of the ends of the bed. I suppose that, since I'd be cutting the stripped bed, I should have enough length to join that rack to the original rack, but quite how to do this is the puzzlement...but then, I'm easily puzzled.

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          • #6
            As I said above I don't really know your lathe other than what lathe's UK shows, so just trying to imagine what your up against.

            With the rack it looks like it is just bolted on and probably doweled, so you would just use the rack off the spare bed and mount it over the join and allow it to go as far as needed. If it ends up to short you would need to find another piece of rack, or make a piece up.

            If the surface is just rough cast where the rack has to go on the side of the bed, you will need to have the bed machined in that area.

            Dave

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            • #7
              My lathes rack is made of more then one rack where it is joined at the root of two teeth, since the rack is just used for power feed, its not 100% critical, just get it aligned and as gapless as you can.
              Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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              • #8
                I've considered this project myself, but never really got right into it.

                It,s a pretty basic bed i see no reason it cannot be done, as far as the rack, either join two together, or get a new longer one cut.
                Probably easier and better to just get a new one made.

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                • #9
                  Just an idea, what if you cut the ends off the spare bed, cut you bed in to & put the spare bed portion in the center?
                  "Let me recommend the best medicine in the
                  world: a long journey, at a mild season, through a pleasant
                  country, in easy stages."
                  ~ James Madison

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                  • #10
                    The thought that comes to my mind, is thermite welding, such as they use for joining railroad track.

                    May not be practical in this case. Would certainly require the utmost precision in the welding, AND some grinding and/or scraping afterward.

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                    • #11
                      Black Moons has the approach, cut and butt together on the root between two teeth. There is no need to go to extremes with welding, scraping and such here, just use a modicum of care and it will turn out fine. If you have a bit of the rack left over, it can be used as a gauge to achieve proper spacing when fitting the two pieces together.
                      Jim H.

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                      • #12
                        I was referring to the lathe bed, not the rack.

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                        • #13
                          Joining the beds

                          Hello, I really appreciate all the input. Thank you, all!
                          My thought had been to use machine screws to join the two beds, i.e., drilling horizontally through both and tapping one of them. Another alternative derived from a plan in Projects Four is a splicing plate that would hold the two bed sections together, but could be removed when wanted. This latter approach, of course, would necessitate removing the splicing plate whenever one wanted to move the tail stock either on or off the added section...if that makes any sense. The original drawing from a fellow named Robert W. Metz, illustrates a beautifully simple approach, but does not cater for powered apron (or come to that, any apron at all). I would attach one of the two pages from the Projects Four that have Mr. Metz's design, but I can't figure how to attach anything to this thread.

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                          • #14
                            With my 12x36 Chinese lathe the rack is in 10inch to one foot sections joined together to make up the length, and the are doweled and bolted to the bed. They must has a machine that makes this length pieces and be economical as there all like that.
                            There is also a short piece of rack that goes on the gap for the US left hand hand wheel guys, where the short piece of rack is on the tailstock end for us right handed guys.
                            I know yours is not like this, but just shows even the factory join them together.

                            With the attachments you have to host them elsewhere like photo bucket, etc.

                            Dave

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                            • #15
                              You would be better served to sell your present lathe(s) and get something bigger. Once you start cutting and joining, without the proper equipment, it's probably going to be a mess.
                              The shortest distance between two points is a circle of infinite diameter.

                              Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

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