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Help with backing plate for indexing head?

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  • Help with backing plate for indexing head?

    About a year ago- I got a freebie of a old LW indexing head that looked very neglected, but after lots of hours of full dismantle, cleaning, lubing, etc.. it has been restored to silk-like operation.

    Problem is, it didn't come with any chuck. And it has an oddball thread size of 2-1/4 x 10:

    Now that I'm much more confident in doing threading, I have several projects where I could put this old girl to good use. Since I can't seem to find any off the shelf chucks or backing plates with that thread, looks like I'm going to have to make one.

    I've never tinkered with any chuck-with-backing-plate configurations, only switching out chucks on my lathe. So I have several questions about doing this operation.

    What type of chuck do I buy to attach a plate to?
    Best choice of steel type for making a backing plate?
    What thickness would you make the plate?

    And on the LW unit pictured above, does the plate/chuck just screw onto the threads, or should there be some sort of locking mechanism to secure onto the threads so it doesn't want to "unscrew" while under milling forces in use?

    Thanks for the help, I'm sure I'll have lots more questions about this as I go......

  • #2
    I'm not sure if this will be of any help but take a look at this link:

    If it were me I'd probably make it out of cast iron which can be bought as slices of a round from the various metal suppliers or possibly use a semi finished back plate of a smaller size to bore and machine to the required thread/diameter. Perhaps one of these would have enough extra meat.

    I have seen unthreaded blanks advertised in HSM as well and they are another option. Lastly, if I were really pressed for material I might consider a slice of aluminum round.

    One other thought would be to make an adapter that uses the chucks you currently use on your lathe. That way you could simply transfer the chuck, with the work undisturbed from the lathe to the indexing head negating any runout induced by using a different chuck. You could also make a driving device like the one in the photo of the 203-4000 shown in this link to the Enco catalog and place your work between centers.


    • #3
      There's a whole LW unit on ebay right now going for almost a grand... But at least I can see the correct chuck on there:

      Looks like is just screws on tight and that's it.
      Shure would like to find one of these original chucks, long shot I know.
      I like how compact it is to the body of the unit compared to making a backing plate and then mounting to that....


      • #4
        T. Hoffman,
        For chucks you'd want what are called Plain Back chucks. You machine a backplate to fit your spindle, Then machine the backplates O.D. and bolt holes to fit the chuck. You'd bolt the backplate to the chuck to provide the interface. For a face plate, Bison sell larger cast iron blank backplates without any machining done. With one of the correct size you could build a faceplate for a direct mount to your spindle. I've only mentioned Bison but I'm sure there's others that offer the same types of chucks and blank backplate castings. To be honest most work using a dividing head like this requires high accuracy so maybe a independant 4 jaw chuck would be your best way to go. Hopefully some of this helps. Nice job cleaning that head to like new condition. One further thought. Depending on your experience level and the complexity of your dividing head spindle you could make a new one to duplicate your lathes spindle. That way everything is interchangeable.

        Last edited by uncle pete; 08-29-2011, 07:37 PM.


        • #5
          I've got the little brother of yours and it takes 1 1/2"-8 chucks so I have a couple that will go right on. I would bet that if you buy a back plate for a 1 7/8" thread, there is probably enough meat to open it up to your thread. You just need to decide what size chuck to use. I would bet an 8" would be about right. Here is one example

          I've got an L00 back plate from him and it is nice.


          • #6
            I don't know anything about it, but... it looks like from the picture there is a taper on the nose there. Could it be that it takes some kind of collet too?
            VitŮŽria, Brazil


            • #7
              Post deleted, misread catalog


              • #8
                Most dividing heads use a 6 are 7 inch chuck. I prefer a 6 inch set true 3 jaw on mine. The backing plate can be made of cast iron are steel.
                Every Mans Work Is A Portrait of Him Self


                • #9
                  That spindle nose taper looks like a 5c but I could be wrong. Sharp eyes David.



                  • #10
                    Originally posted by davidwdyer
                    I don't know anything about it, but... it looks like from the picture there is a taper on the nose there. Could it be that it takes some kind of collet too?
                    Yup, on my unit there is a thru-hole and draw bar on the opposite side. I *think* it may be for 5C, but not sure. I've seem to have read that LW's had other collet tapers in there, so I really don't know.

                    I don't have any 5C collets yet to check it.

                    If it is 5C, I have also thought about some of the 5C-to-chuck adapters I've seen around too:

                    What's the best way to check/measure if it is indeed a 5C collet taper on my LW?


                    • #11
                      Check the 5C dims at Zagar, or on OWWM, etc. If it looks close, get a $5 collet and see.

                      But, if you have a reasonable collet, like 5C (I spotted that taper also), you have a good way to hold mandrels for gear etc already, no need for the chuck.....

                      I have a 3.5" LW, and I have yet to put on a chuck..... (its 1 1/2-8). I usually use a mandrel with center and T/S, and a dog driver that captures the dog tail with setscrews.

                      Ya, if you want to make dividing plates or that sort of stuff you likely want a chuck for one-sided workholding, but the collets or dog driver are more secure against twisting

                      Keep eye on ball.
                      Hashim Khan


                      • #12
                        Adapter plate

                        I used a plain back four jaw chuck on a steel plate of about 5/8 thickness when I finally fitted a chuck to my 6" vertex .

                        The four jaw makes life easier when cutting special shapes to replace previously cast items.

                        I would make an adapter that would also allow you to transfer the chuck to and from your lathe if possible .

                        That allows a lot of versatility when working on projects.


                        • #13
                          Originally posted by T.Hoffman
                          About a year ago- I got a freebie of a old LW indexing head that looked very neglected
                          It doesn't look neglected now...very nice job...can I send you my Elliot



                          • #14
                            Lovely restauration job - well done.

                            On the chuck unscrewing, I'd also be bothered about that. If you indeed make a backplate that threads on, how about then adding a through-spindle drawbar. Tightening this should reduce the chance of unthreading - especially if you use a left hand thread.

                            I can think of other ways - picking up on the spindle's internal keyway if there is one and using a loose threaded ring to hold the chuck on, but much more complicated.
                            All of the gear, no idea...


                            • #15
                              A chuck on a dividing head is not like that on a lathe - it doesn't get massive forces put through it. This will depend on what you are doing of course, but for drilling holes or cutting gears (force towards the spindle) there is not going to be much trying to unscrew your chuck.
                              I want to put a camlock adaptor on mine so I can swap chucks between dividing head and lathe. To lock the adaptor onto the D/H I was thinking of a grubscrew with a brass tip.
                              Most D/H's I've seen have a 3 jaw as the chuck. Unless you are going to stuff that is not round, I'd suggest that is the better way to go. If you think about centring work in a lathe 4 jaw it usually takes (minimum) a couple of revolutions. On a D/H that is a lot of cranking. I'd also suggest the smallest chuck that you can get away with - a 6" or maybe even a 4". My latest D/H has a 8" and I almost bust a gut getting it mounted. If you make up a faceplate at the same time you make up the backing plate, you can cope with less regular shapes that way.

                              My thoughts.