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Dumb idea or not - adapting a dead center to take a threaded drill chuck

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  • Dumb idea or not - adapting a dead center to take a threaded drill chuck

    so, my ancient lathe of dubious lineage has a bespoke non-tapered tailstock:



    with a threaded dead center (5/16 20 I think, RH thread) that has some sort of graduations on the top and a key on the side to stop it rotating as it's screwed in and out



    I'd really like to add a drill chuck to the tailstock as it would be incredibly useful for a lot of things, but I'm a bit stumped by how to do so. One way is to make a new threaded keyed center with an appropriate taper (JT3?) or threaded end to accept a drill chuck. However, that's quite some what beyond my abilities and tooling right now (however clear the theory may be), so another option is to thread the tip of the existing dead center to accept a chuck.

    It's 10.9mm diameter at the narrowest, which is 27/64in in old money (bleh, imperial) which in turn is a sniff wider than 3/8 which appears to be a common thread diameter for 1/2in chucks. My lathe doesn't have any horsepower, hamster power perhaps, so there's no point going larger.

    Now, I can turn down the center to the correct diameter for a 3/8 24 die (which I might even have). But, would this be true enough to be useful or will I end up with horrendous run out from the chuck? I'm looking at a 2nd hand Jacobs keyed chuck off eBay as there seem to be enough of them at a price I can afford.

    Any other ideas? It would be really neat to be able to mount a live center at some point, but I could always machine and tap an adapter for that.
    Last edited by mattthemuppet; 10-18-2013, 05:27 PM.

  • #2
    The dead center is probably quite hard and therefore tough to machine. You can buy a variety of chuck adapters (from MSC and others) that would be easier to modify.

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    • #3
      Would an adapter with two different threads work? http://www.mcmaster.com/#standard-threaded-rods/=ozrwtg Put a spacer around the adapter so the chuck tightens against the spacer, not just on the threads.

      Drill chucks are rarely centered very accurately, so I doubt a little runout will be much of a problem.
      Any products mentioned in my posts have been endorsed by their manufacturer.

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      • #4
        Originally posted by HWooldridge View Post
        The dead center is probably quite hard and therefore tough to machine. You can buy a variety of chuck adapters (from MSC and others) that would be easier to modify.
        good point. I had a look at some of the chuck adapters, but I couldn't find any for less than eye watering amounts and they'd still require drilling and threading for the hand crank

        Originally posted by winchman View Post
        Would an adapter with two different threads work? http://www.mcmaster.com/#standard-threaded-rods/=ozrwtg Put a spacer around the adapter so the chuck tightens against the spacer, not just on the threads.

        Drill chucks are rarely centered very accurately, so I doubt a little runout will be much of a problem.
        thanks for the idea, although I'd need an internally threaded to externally threaded rod to be able to use the hand crank. McMaster had some one-threaded-end rods on that page you linked, but there wasn't anything with the right dimensions. I'd still have to drill and tap the center for the hand crank thread, although I might be able to use a lathe at work to do that.

        I'll check the dead center for hardness and if it's too hard, I'll see if I can sweet talk the machinist at work into showing me how to use his mill and lathe.

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        • #5
          Sorry to doubt you, but are you SURE that center can't be knocked out?

          allan

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          • #6
            Drill with the compound slide? Not sure what kind of toolpost you use, but basically anything that would hold a boring bar can also hold a drill chuck shank. Line up the rear center mark of the shank with the center point of your tailstock for expediency if it helps. My personal take is to go for broke or don't go at all. IOW make a new, MT1 quill, or don't do a thing. There's no functional difference in using the compound slide. Both it and the tailstock are screw advanced. The only difference is a small amount of time in setup... 'better than possibly ruining your only functional tailstock.
            Last edited by Arthur.Marks; 10-18-2013, 06:14 PM.

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            • #7
              Originally posted by kitno455 View Post
              Sorry to doubt you, but are you SURE that center can't be knocked out?

              allan
              doubt away, I completely hadn't thought of that!

              Originally posted by Arthur.Marks View Post
              Drill with the compound slide? Not sure what kind of toolpost you use, but basically anything that would hold a boring bar can also hold a drill chuck shank. Line up the rear center mark of the shank with the center point of your tailstock for expediency if it helps. My personal take is to go for broke or don't go at all. IOW make a new, MT1 quill, or don't do a thing. There's no functional difference in using the compound slide. Both it and the tailstock are screw advanced. The only difference is a small amount of time in setup... 'better than possibly ruining your only functional tailstock.
              I've no objection to that at all, I'd just have to mill or grind down the drill chuck shank to 1/4in width 3/8in height. Not beyond the realm of reason by all means. I have some flexibility with regards to center height too, which might be useful when holding endmills to rough finish a blind hole. It'd certainly be a simple option too.

              I'd love to make a new quill with an appropriate thread or taper, it's just beyond my abilities at home - there's no way on earth I can drill down the center of a piece of steel rod with any accuracy using my hand drill I'll go bother the machinist at work next week and see what he thinks, plus to find out what sort of beer he likes!
              Last edited by mattthemuppet; 10-18-2013, 06:47 PM.

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              • #8
                Which part of your dead center is removable - the conical tip, or the arbor in the tailstock quill (or both?)?

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                • #9
                  mattthemuppet, by your initial post, it sounded as if the possibility of a socket in the quill had already been investigated. That probability that the dead center can be removed is very high. Try and see if a long rod inserted from the back of the quill can knock it free.
                  Last edited by Arthur.Marks; 10-18-2013, 06:56 PM.

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                  • #10
                    Originally posted by dp View Post
                    Which part of your dead center is removable - the conical tip, or the arbor in the tailstock quill (or both?)?
                    the arbor in the tailstock quill - I haven't tried to remove the tip yet, partly for fear of getting it back in again!

                    Originally posted by Arthur.Marks View Post
                    mattthemuppet, by your initial post, it sounded as if the possibility of a socket in the quill had already been investigated. That probability that the dead center can be removed is very high. Try and see if a long rod inserted from the back of the quill can knock it free.
                    I'm sorry, I'm still learning the lingo, hence not being especially precise with my description. I'll find an appropriate sized rod and give it a smack tonight or over the weekend. I'm guessing that if I can get it out, I should be able to get it back in again.

                    By a "socket in the quill", do you mean some sort of commonly available adapter? If it's something I can press in I'm pretty sure I'll be able to make it myself. I have a small piece of steel rod kicking around in my box of random metal chunks which could work..

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                    • #11
                      I am leaning towards the suggestion Arthur made regarding use of the compound slide...or similar, perhaps there are other options you have not considered...

                      there's no way on earth I can drill down the center of a piece of steel rod with any accuracy using my hand drill
                      just saying, what happens at the headstock end in terms of threading of the spindle, or interior taper of that spindle...I am thinking figure out a mount for the compound or cross slide, mount some material in there and drill using the headstock end and moving the material rather than moving the drill (as would be the case with a drill chuck attached at the tailstock)...when I first got my lathe the tailstock was non-fuctional due to previous owner and broken bits so that needed repair and was, by and large, done on the lathe itself.
                      You might be able to drill through a steel rod that way but you might also be able to mount a lump of metal in place of the toolpost, drill/bore that out in a similar fashion to a size that matched some arbor with a straight shank and then mount your drill chuck on that arbor [functionally it should be close to the same as being held in tailstock]

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                      • #12
                        Originally posted by mattthemuppet View Post
                        I'll go bother the machinist at work next week and see what he thinks, plus to find out what sort of beer he likes!
                        Why not bring your tailstock quill to work and get a little professional help? Maybe the machinist could scrounge up a drill chuck and matching taper arbor.

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                        • #13
                          Originally posted by mattthemuppet View Post
                          By a "socket in the quill", do you mean some sort of commonly available adapter?
                          I mean, the quill most likely has a tapered hole in the end. The solid center has a tapered section that matches. When the solid center is inserted into the tapered hole, the two are held in place by friction. The shallow angle of the taper acts like a self-securing wedge. There are an incredible number of standardized tapers in the machine tool trade. Nearly all lathe tailstocks, though, prescribe to the "Morse Taper" standard.

                          Most lathe tailstocks use the advancement screw to remove the tool from the quill. This works by turning the handwheel until the quil fully retracts into the tailstock. If you keep turning the handwheel, the screw contacts the back of the center and pushes it out. Sometimes, a center has been used that is too short. The screw cannot reach it. In these cases, it may be necessary to completely remove the screw (as you have in the above picture) and insert a rod through the threaded hole in the quill. Use a rod sufficiently long to extend out the end of the quill. Then the rod can be hit firmly with a hammer. Be careful to place a few rags or shop towel on the bench... the center may dislodge suddenly and come shooting out!

                          IF you find that the center is indeed removable, post some pictures with a couple measurements. Members here can help you identify the taper series used.

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                          • #14
                            I agree- it's very likely that the arbor can be removed. If not, then machine something to fit over it like a socket and prepare the other end to accept the drill chuck. You can buy arbors ready to go, as someone mentioned.

                            I probably could not do without the drill chuck in the tailstock. It's handy for many things, not the least of which is holding a drill bit. With a little persuasion from a scrap held in the tool holder, the tip of the bit can be forced to begin cutting on axis and a relatively straight and aligned hole can be drilled. Amongst other applications, I use my setup to press a workpiece against a faceplate so it can be machined without requiring a center hole.
                            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                            • #15
                              Oh, so this is all one piece?



                              I thought the tip screwed into the barrel.
                              Any products mentioned in my posts have been endorsed by their manufacturer.

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