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Lathe Chuck Size

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  • Lathe Chuck Size

    After I sold all my machinery (about 20 pieces)(health reasons)I realized that I really wanted to have a few things to work with and so am buying smaller and much less expensive things. I hope to get a Logan/Powermatic 11" lathe that passed through my hands about 6 years ago. The problem is that it is a basic lathe, no chuck, no tool post, no tailstock center, no tooling. My question is should get a 6" chuck like was on my Grizzly G4002 or an 8" chuck that was on my Clausing 5914? Either way, it won't be top of the line, just something I can do some basic non-critical turning with. 6" or 8", that is the question. It will be 3 jaw with two piece jaws. If memory serves me, it is 2¼"-8 thread mount.

    Thank you,
    Last edited by CPeter; 05-23-2023, 05:31 PM.
    Grantham, New Hampshire

  • #2
    Get a 6" chuck. It probably would be sufficient for 95% of your work.


    • #3
      For my 13x40 lathe I have 4",6",7" and 8" chucks in 3 jaw. One 8" 4 jaw. I use the 6" most always. Rarely do I use a different size.


      • #4
        I have a 6" and 3" (3 jaw) chuck. For small stuff, I use the 3" chuck. especially when clamping on the outside of the jaws. The 6" chuck is large enough to hold a Hex collet (ER32) holder. When I have time, I will make an arbor so the 3" chuck can be mounted in the 6" chuck.


        • #5
          An 8" will certainly fit. But 8's are a bit of a lump and a half to change where a 6" can be handled purely by hand. An 8" is heavy enough that you'd want a wooden carrier that rests on the ways and holds the chuck at spindle height.

          My 12x36 came with a 6" 3jaw and an 8" 4jaw. I always figured that I might "upgrade" to an 8" 3jaw. But for that once in a decade situation where I needed a larger grip I just use the 4 jaw instead. For 99.9% the 6" is just fine. And the lathe spins up and slows down so much faster compared to the 8" 4jaw that I prefer the lighter 6" chuck for day to day uses.
          Chilliwack BC, Canada


          • #6
            Possibly better to get a faceplate rather than a huge chuck. The faceplate will hold almost any large lump of metal as long as you can clamp it. Chucks are more limited, but easier to use.

            The biggest faceplate you can fit is usually the best one to have. Extra points if it has threaded holes instead of just slots.
            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.


            • #7
              Originally posted by CPeter View Post
              ...I hope to get a Logan/Powermatic 11" lathe that passed through my hands about 6 years ago. The problem is that it is a basic lathe, no chuck, no tool post, no tailstock center, no tooling. My question is should get a 6" chuck like was on my Grizzly G4002 or an 8" chuck that was on my Clausing 5914? Either way, it won't be top of the line, just something I can do some basic non-critical turning with. 6" or 8", that is the question. It will be 3 jaw with two piece jaws. If memory serves me, it is 2¼"-8 thread mount.
              You must already know--that is the worst possible way to buy a lathe--bare.

              Before getting the Monarch 10EE I had a Logan 12 x 35, which came from the maker with a 6" 3-jaw and 8" 4-jaw. That setup was good for most of my needs, but I sometimes wished for a larger 3-jaw. Cheap chucks are cheap, get whatever you want. 2-1/4"-8 is correct on the spindle.

              12" x 35" Logan 2557V lathe
              Index "Super 55" mill
              18" Vectrax vertical bandsaw
              7" x 10" Vectrax mitering bandsaw
              24" State disc sander


              • #8
                Who said anything about "buying"? This lathe came from a school with no metal working program. There were two and I had both and gathered up everything for one "complete" machine and gave the other away to a friend who put it in storage and now is giving it back. Probably less than 20 hours of running time on it. I can afford to put a little money into it to do what I need. I agree on the advantages to the 6" and will go that way. I never could find all the missing pieces but it was purchased 40 years ago and had not been turned on for the last 20 that it was in the school. It ran OK, but I think the paint was better on the one I kept (they were pretty much equal as far as condition).
                Grantham, New Hampshire


                • #9
                  By the way, when I said that an 8" can be quite a lump to handle "freehand" I learned my lesson many years ago. Here's the combo saddle and carrier that let's me lift the chuck into position and then spin it onto the threaded spindle nose. I CAN manage the weight but it's a pretty iffy thing when you're trying to two hand it onto the threading and turn it on those first couple of turns until it's "safe". Same with taking it off too. This saddle thingie just takes away all the concern and risk.

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                  The 6" I handle "freehand" other than an "oopsie" board on the ways for the chance that I might slip.

                  Mind you, if I do slip and it ends up on the floor or my foot then there's gonna be some serious hand wringing, colorful language and perhaps a little crying... I'm starting to think that at least a "safety dowel" stuck into the jaws and extending back into the spindle would be a good idea to hold it as it comes off the threads.

                  In fact..... Give me a few seconds.....

                  I found a roughly 18" piece of old PVC tubing. It sticks out like this and extends about 8 inches into the spindle. Long enough to unthread then ease it out and grab the other end of the tube. And if it did slip it would just hang there.

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                  Chilliwack BC, Canada


                  • #10
                    My rule of thumb for home shop sized lathes is 2/3s (0.66) of the swing. So 11" x 0.66 = 7.33". Past that I don't know and 8 inch IS past that. I would not buy the 8 inch unless I had all the dimensions to be sure the jaws are not going to hit the ways. Considering the possible interference with the ways, you may actually be able to hold larger diameters with the 6 inch chuck (also see PS 2, below).

                    And you mention health reasons. I assume you are referring to the weight that needs to be lifted. I am in the same boat. I would guess that a mounted, 8 inch chuck will weigh about twice what a mounted 6 inch will. Or more (8/6^3 = 2.37).

                    Unless I had a positive need for the 8 inch, it would be the 6 inch for me.

                    PS: Some years ago when I was looking at a new chuck for my SB-9, members of this board advised that a 6 inch was too big. They said a 5 inch was better. I did get the 6 inch and it has worked out fine. But it is about the biggest chuck my lathe could effectively use. (9" x 0.66 = 6") See, my rule of thumb works.

                    PS 2: When I purchased a vise for my mill, many suggested a 6" size. I did a lot of checking and found that on my mill, with it's arrangements of table slots, a 5" would allow me to hold larger work pieces within the work envelope of the machine. So I saved money with a smaller vise and can hold larger parts in it. Bigger isn't always better. I talked myself into buying a second, identical vise, partially with the money I saved. So that allows much wider parts to be held inside that work envelope. You gotta check the details.
                    Paul A.
                    SE Texas

                    And if you look REAL close at an analog signal,
                    You will find that it has discrete steps.


                    • #11
                      Paul, I very much did run into the issue of jaws fouling the ways. It was on the old Myford ML7 where I tried it with a 5 inch Bison. 7 x 0.66= 4.6". And that last 0.4 did bite me in the backside. There was a lost range of holding between the inside jaws just before they struck the bed and the outside jaws used at minimum.

                      I ended up with a 4" for the Myford.....
                      Chilliwack BC, Canada


                      • #12
                        I bought a new 8" Bison 3 jaw when I was just starting out with my first lathe,
                        a 10" Atlas. I was happy I did. It allowed me to make some heavy duty axles
                        for an off road project. The jaws would contact the bed if they were at their
                        outer extremes, but you were in the region of running out of scroll anyways
                        at that point. If you really want to make a rule, maybe you should run out of
                        scroll before the jaws hit the bed. But after I sold the Atlas lathe, I kept the
                        chuck and used it on a bigger lathe. I really think for an 11" lathe, and 8"
                        chuck is going to fit and allow a larger work envelope. But what kind of stuff
                        are you making? Piddley little shaft work, a 6" will be fine. Acutal project work
                        I would get the larger chuck.



                        • #13
                          I would go for a 6", or 160mm three jaw scroll and an 8", or 200mm four jaw independent. The 4 jaw would not be used as often, but would be very useful, occasionally. If you intend to do any work under 1" diameter, a 4" , or 100mm chuck is handy.
                          I have bought a 200mm four jaw independent for the 12 x 24 Atlas, because the other lathe at the museum, a Smart & Brown is only a 9 x 20. A mandrel to fit in the chuck which is a sliding fit in the Atlas spindle bore one end and the chuck through bore size at the other will make the chuck much easier to mount and remove without damaging the bed or fingers.
                          Last edited by old mart; 05-24-2023, 01:48 PM.


                          • #14
                            Peter, is this the Logan you're getting?

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                            I don't know why but when you mentioned 11" and the Logan/Powermatic I was thinking it might be a bigger and heavier machine. I didn't realize that Logan had made this size overall in an 11" model. Turns out ( that this is the same bed with different headstocks and tail stocks for the 9, 10 and 11" versions. The 11 having a better size spindle. So bonus on that.

                            I've worked with this size Logan some years ago in a shop I had occasional access to. It's a lovely machine for the size. But it is light enough that I think a 6 inch 3 jaw would be a far better fit than an 8". The issue being that the 8 at higher speeds would result in a much longer spin up and coast down time when doing operations that require a lot of measurement checking.

                            I'd back it up with an 8" four jaw to permit holding larger items as needed and also for times you need to do offset turning or hold square and rectangular items. The longer spin up and coast down being more livable since it's not a regular deal.

                            To that I'd also add a collet setup. Which one? I'm thinking one of the low cost ER32 or ER40 flange chucks on a thread mount backing plate.

                            Chilliwack BC, Canada


                            • #15
                              These were the two when I had them 6 years ago.Click image for larger version

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                              Grantham, New Hampshire