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How do you measure swing on a lathe?

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  • How do you measure swing on a lathe?

    Do you measure from center,diagonally to a way?
    Or measure vertically to a point half way between the ways?

    One measurement makes my machine a twelve inch.
    The other way makes it a thirteen inch.

  • #2
    I would measure from the centre-line to the nearest thing it will touch, since that is what matters to what you can mount in the chuck.
    Peter - novice home machinist, modern motorcycle enthusiast.

    Denford Viceroy 280 Synchro (11 x 24)
    Herbert 0V adapted to R8 by 'Sir John'.
    Monarch 10EE 1942

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    • #3
      I am probably inconsistent with the world on this but I consider it the largest diameter at which you can remove metal. It may be possible to get a large swing with a gap bed but if you have no tools that will reach the OD then you have a large swing area within which you have a smaller work area. For me the swing area is nice to know but what I need to know is the working diameter. And of course I'm limiting my definition to home shop machinist class machines.

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      • #4
        There are two different ways to measure the swing.

        One is the swing over the ways. Find it by measuring from the axis of the lathe to the closest point on the ways, typically the top of the V on the back side of the ways then multiply it by 2.

        The 2nd is to measure from the axis to the top of the cross slide. Again multiply by 2 and you'll have the swing over the cross slide.

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        • #5
          North America uses the swing IE: the diam that can be turned over the bed.

          England and other "colonies" use the center height IE: the distance from the lathe center to the bed or 1/2 the swing.

          I use the cat method. Tie a cat by its tail to the center of a chuck and turn the lathe on. If the cat doesn't survive then you didn't have enough room to swing a cat by it's tail.
          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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          • #6
            Loose Nut, sounds like about the same to me. Moral of the story buy a big enough lathe or own a small cat. Seems to me the larger production lathes measure over the cross slide while the smaller cheaper models measure over the ways, My American Pacemaker is tagger a 14" but measures 17"+ to the ways. Just my opinion.
            "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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            • #7
              Originally posted by loose nut View Post

              England and other "colonies" use the center height IE: the distance from the lathe center to the bed or 1/2 the swing.
              Not always. My Denford '280' swings - 280mm diameter.
              Peter - novice home machinist, modern motorcycle enthusiast.

              Denford Viceroy 280 Synchro (11 x 24)
              Herbert 0V adapted to R8 by 'Sir John'.
              Monarch 10EE 1942

              Comment


              • #8
                Myford ML7 or Super7 = 7" swing, but was advertised as a three and a half inch lathe.


                .
                Thomas

                Problems worthy of attack prove their worth by hitting back
                - Piet Hein

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                • #9
                  Originally posted by Thomas Staubo View Post
                  Myford ML7 or Super7 = 7" swing, but was advertised as a three and a half inch lathe.
                  .
                  Thomas,

                  The 7 in ML7 was merely the next model number after the ML6. My ML4 is also a 3 1/2" lathe. I believe the ML2 was 3 1/2", and the ML1 and ML3 were 3 1/8". The ML8 was a woodworking lathe.

                  George

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                  • #10
                    Seems there was a time when 'swing' meant the length of stock one could swing arount the center without hitting anything. Then, just like with hp ratings on electric motors, as soon as somebody started using the term to describe max stock diameter, everyone followed along.

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                    • #11
                      Originally posted by Peter. View Post
                      Not always. My Denford '280' swings - 280mm diameter.
                      My reference was back in the pre-metric/EU days, the Myford 254 was a 10" lathe
                      The shortest distance between two points is a circle of infinite diameter.

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

                      Comment


                      • #12
                        I use the cat method. Tie a cat by its tail to the center of a chuck and turn the lathe on. If the cat doesn't survive then you didn't have enough room to swing a cat by it's tail.[/QUOTE]


                        Thats sum funny crap right there!!

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                        • #13
                          I sort of looked at it as a regular kids swing- how long are the ropes- 8 ft long, that's the swing, even though it would sweep out a 16 ft diameter. But I do think it's a point to keep in mind that it's specified different ways. No point in buying a replacement lathe that's 'larger', only to find out is won't swing as much as the old one.

                          I look at swing over the cross slide the same way- in terms of radius, not diameter.

                          What dp said is interesting. I've run into this several times- not being able to position a tool to a point where you could cut on the outside diameter of a workpiece. If the tool can't reach, then the machine doesn't have the capability- at least without modifying it. You would have to define the worn 'turn'. Usually that means remove material, as in 'turn the piece down', but it could be taken as simply rotating the part without having it smash into things.

                          My lathe should be called a 2-7/8 (swing over cross slide)
                          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                          • #14
                            I am trying to id an old Sebastion lathe.
                            I can find some info on thirteen inch but no info on twelves.
                            So I will rephrase the question: How do the lathe manufacturers measure their machines?

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                            • #15
                              The usual I've seen is to tell what is the maximum diameter over bed and the maximum diameter over the saddle, as both are quite necessary to know if planning work for the machine. Plus the maximum length between centers of course.
                              Amount of experience is in direct proportion to the value of broken equipment.

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