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Dead Center Spindle Adapter

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  • Dead Center Spindle Adapter

    I still have one glaring deficiency in my workholding ability in that I don't have any way to mount a center up in my spindle. It's a 11" Logan and I believe it's a proprietary taper. The manual is strangely silent on the issue and I've never seen any info anywhere that would lead me to believe different.

    Big Bucks from Logan and I haven't seen one on E-Bay in over a year of looking. So I'd like some advice on how to make my own. Please be aware that any tapers I've done so far have been completely accidental and respond accordingly!

    First, material. Would something as soft as HRS be OK? I've got a 2 ft length of 2.5" round out there that would let me make a lot of mistakes. It doesn't cut real pretty but it also doesn't take much to polish it up real smooth.

    DTI in the compound to set the angle? How good does the compound have to be .... because mine sucks! I'd like to develop the skills to fix it someday but it is what it is for now.

    I'm thinking I'll make a threaded arbor to hold it in a chuck. That way I can unscrew the chuck and turn it around for test fitting without losing center. But if I'm way off base on this idea please let me know!

    I've read about bluing for checking the fit but never done it .....

    Assuming I get the outside right, what size MT for the interior? Got a 1 3/8" thru hole in the spindle.

    As always, any tips, advice, or general slapping about the head is appreciated. You guys are gonna make a machinist out of me someday.


  • #2

    Just change the outer dimensions to suit.


    • #3
      Obviously you need to identify the taper if you can. Either borrow one (best if you can) or get the specs. I bet Scott would give them to you.

      Then get a suitable bit of material. I've got the OE for my Rockwell, it seems to be hardened tool steel, and has MT2 inside for the similar sized spindle ID (to yours). That was fairly typical, but I don't like MT2 on one end, and MT3 in the other. Makes sharing tooling a pain as you might manage. Stupid idea on their part, but they all did it, so I have to guess there was some reason.

      I found an MT3 adapter I thought would fit. But it proved to be some sort of Jarno and just a bit too big. It's also hardened, but not much, and it can be cut. My plan was to cut it to match. But it's hard to hold with an MT3 ID that needs to be dead perfect. So I've been thinking for a while. One thing I will do when done, is clearance the center 1/3 to make fitting easier. Normally that bushing does not transfer torque, and from what I hear (I don't know) the clearance has minimal effect on load transfer due to the correspondingly large taper ID to OD. But alas, I had nothing but drill arbors to use as mandrel and it just made for a real PIA and it never got done.

      That said, I recently came into some MT3 ground and hardened extension sockets that provide a very nice option for mandrel. I think I shall soon revisit this myself to finally finish that project. At the same time I'm also making an MT2 for a friend (another poor Rockwell soul... ) who has none.
      Master Floor Sweeper


      • #4

        Good topic - I need one of these too...

        My lathe has a headstock taper that's also not a Morse - it's somewhere in size between a 6 and 7MT (65mm spindle bore). The eventual taper bore needs to be a 5 MT, same as the tailstock.

        Starting out with a 5 to 7 MT reducer sleeve seems like a good idea. These are usually hardened; can they be turned using carbide? Maybe a Chinese one would be easier to cut.

        Can't say I've seen much 7MT stuff on Ebay though...

        All of the gear, no idea...


        • #5
          On the hardness and existing taper I do have a 5C adapter for the spindle. It fails the hardness test in that I can mark it with a file ... Seems soft. I wouldn't know how to model the OD of it tho.



          • #6
            Logan taper

            You have the small end=thru hole.
            What is the big end messurement?
            How long is the taper?
            With those messurements I am sure we can figure out what taper it is. Could it be Jarno taper? Brown and Sharps? Get the messurements and let us figure itout.



            • #7
              You can get the reducing sleeves in hardened, or with the tang only hardened..... I got a 5 to 4, cut the tang off and made up a 5-C collet closer for my 12x36. I got mine at KBC, but they're probably availiable at most of the big suppliers.

              But, your right Ian, not much size 7s though... at least on this KBC page #406

              If everything seems to be going well, you have obviously overlooked something........


              • #8
                Apparently there are two possible tapers. It changed at some point.

                But, WHO CARES?

                All you need to know is what you already know........ you HAVE the taper right there.

                So set up an indicator on the compound, and line compound up with the taper.

                be sure you get the point of the DTI right on the spindle center height, which will be where it gives max reading as you raise and lower it with the indicator holder (one with the arm and the adjuster).

                Then get a piece of stock of sufficient diameter, and cut the outside taper. A couple checks with blue and you should have one that fits, even if you don't know what taper it is.

                Then set the compound up with Morse 2 taper (use t/s as model) and drill and bore the adapter for MT2 while it is installed in the spindle. That will get max accuracy, especially if you mark orientation and always put it back like that.

                I doubt you will need it hardened, if it ever gets to be unusable, you have the model right there to make another.

                Keep eye on ball.
                Hashim Khan


                • #9
                  ...what J Tiers said.

                  I think your idea of holding it in a chuck, and unscrewing the chuck without removing the work, for test fits, is sound. I'm not sure why you say you need an arbor though -- as J Tiers said, do the center taper in place, AFTER the adapter is in place.

                  Morse #2 ought to be big enough. I see no reason for anything larger, and #2 centers are cheaper than #3 (or #4, or #5...) centers.

                  I wouldn't worry about hardening and all that. It's not a "wear" item. Just show reasonable care when using and don't beat on it. You can always make another in 20 years, if need be.

                  I think I might get a decent piece of steel to make it out of, like 1144, but your generic HRS will work.
                  Try to make a living, not a killing. -- Utah Phillips
                  Don't believe everything you know. -- Bumper sticker
                  Everybody is ignorant, only on different subjects. -- Will Rogers
                  There are lots of people who mistake their imagination for their memory. - Josh Billings
                  Law of Logical Argument - Anything is possible if you don't know what you are talking about.
                  Don't own anything you have to feed or paint. - Hood River Blackie


                  • #10
                    Have you checked with Scott at Logan Accutator as to the specs for your lathe?


                    • #11
                      pntrbl, I would call or email the Logan people about the taper angle. I understand the son still supplies parts and help. He can, if he wants to, give you the specs on the taper.

                      If you have a 5C adapter why can't you use that taper to set your compound? You can mount it in a 4 jaw and inticate both ends and then set the compound to the same angle. The problem with the compound is for most tapers the compound will not have enough travel to do the taper in one pass. OTOH, you can make a taper adapter as long as you can and live with it.

                      If you machine the OD taper first and then insert it in the spindle and drill and bore it out. Then set the compound for the MT taper size you want and cut it your sleeve will be very close if not perfectly concentric in your lathe.

                      You can make the taper adapter out of cold roll or hot roll and it don't have to be hard. In the headstock you are unlikely to have the taper spin the issue will be getting the bore clean before inserting the adapter.
                      It's only ink and paper


                      • #12
                        What everyone else said. If you need to turn something between centers, you can always just chuck a piece of 5/8" or 3/4" CRS in the jaws and cut a 60* point on it with the compound. Then have the lathe dog driven by the jaws of the chuck. That way you don't have to remove the chuck and put on the faceplate. Be advised though, you'll want to cut the point again every time you remove the center from the chuck to make sure the center point is concentric.

                        Stuart de Haro


                        • #13
                          I think that may be a Morse 4-1/2. Like the clausing and a few other lathes in the 12" range.


                          • #14
                            That's right, some of the Clausings (the 5900's, 6900's,...) have an MT 4 1/2 spindle. If you have an MT 4 1/2, you can buy the stock adapter from Clausing for around $70

                            If you can post some dimensions (two inner diameters and the distance between the two measuring points), we can figure out what spindle taper you have.

                            Or surely one of the Logan owners here would know.
                            "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."


                            • #15
                              Hopefully this will provide the info you need, there's a bit of from/to ser no/model no and so on in it though.

                              logan taper faq