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Sieg C3 Lathe 7x14 Mounting either a 4 or 5 Inch 3 Jaw

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  • #16
    I thought all the 7x lathes have an integral backing plate as part of the spindle? And the chuck body itself ends up needing to be sized to the step on it and mounting holes drilled and tapped?
    Chilliwack BC, Canada

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    • #17
      I believe the first of these type of lathes only had a 10" bed.
      BC, that's right about the spindle flange, with the use of another lathe, a 100mm 4 jaw independent is easy to modify.
      Last edited by old mart; 12-25-2020, 04:30 PM.

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      • #18
        Originally posted by wmgeorge View Post
        Nope no more shop tools. Trying to downsize and realized that 3 inch 3 jaw was limiting what use I had of the lathe. The 4 jaw I have is 4 inch but can not find the adapter plate?? Did all those 4 inch 4 jaws need a plate??
        Well I checked my machine and the 4 inch, 4 jaw I purchased a few years ago, did not need a backing plate. 4 Holes in lathe plate lined up with the 4 on that chuck? Ok thats great.


        Retired - Journeyman Refrigeration Pipefitter - Master Electrician

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        • #19
          Originally posted by wmgeorge View Post
          Nope no more shop tools. Trying to downsize and realized that 3 inch 3 jaw was limiting what use I had of the lathe. The 4 jaw I have is 4 inch but can not find the adapter plate?? Did all those 4 inch 4 jaws need a plate??
          Do you have the other set of jaws (or maybe separate reversible top jaws)?

          Because with the OD holding jaws, you can hold up to fairly close to the chuck diameter with no jaws sticking out, and all the way to it with a reasonable stickout. Really make smaller chucks more useful.

          I tend to notice that myself, because only one of the 3 jaw chucks has both sets, and I had to swap to the 4 jaw for larger work just to get the holding capability before I got that one.
          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.

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          • #20
            Originally posted by old mart View Post
            I believe the first of these type of lathes only had a 10" bed.
            BC, that's right about the spindle flange, with the use of another lathe, a 100mm 4 jaw independent is easy to modify.
            Thanks, that confirms that.

            Wmgeorge, I'm sure you're not the first to want to fit a 4" 3 jaw onto your minilathe. What does the Great Mini Lathe Modifications Collective out on the web have to say on this?
            Chilliwack BC, Canada

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            • #21
              Originally posted by BCRider View Post

              Thanks, that confirms that.

              Wmgeorge, I'm sure you're not the first to want to fit a 4" 3 jaw onto your minilathe. What does the Great Mini Lathe Modifications Collective out on the web have to say on this?
              I made a zero settable chuck back plate for a Bison 4 or 5" chuck that eventually went to Sid when gave him my South Bend 9c. The mini-lathe I had was the Micromark 7x14. Replaced by the before mentioned South Bend. It can be done, it's just a simple flange that you can add adapter flanges to. I still have that backplate I made, its a huge round chunk of 12L14.

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              • #22
                BCRider is right. The Sieg C3 lathes (i.e., the 7x machines) do not have an adaptor plate per se, but rather a flange which is part of the spindle and acts as a register.

                The C3 comes as standard with an 80mm three-jaw chuck having a recess in the back that fits directly over that flange. Sieg's optional 100mm four-jaw chuck comes with an adaptor plate having the recess for the spindle flange on one side and a larger register to fit the wider recess on the back of the four-jaw on the other. That adaptor plate will possibly fit a standard 100mm three-jaw chuck as well, inasmuch as the register sizes should be the same. The bolt holes for the chuck may be different, but that's an easy enough problem to solve.

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                • #23
                  As I mentioned earlier, I modified the register of a 100mm 4 jaw independent and drilled the body for front mounts to match the pcd of the spindle flange, an easy job, no adaptor required.

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                  • #24
                    In case you guys missed the memo a few pages ago... I have the 4 inch 3 jaw with plate ordered from LMS.
                    Retired - Journeyman Refrigeration Pipefitter - Master Electrician

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