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  • Lathe build underway: Part 1, the spindle

    I am starting a new machine project. My South bend is a very capable lathe but it lacks one thing that often presents a problem. It doesn't have enough swing. It isn't often that I run into jobs that are too long but swing is often a limiting factor. So, I am building a lathe that will solve that problem.

    Rough specs are about 16" swing, 18" between centers, strong as hell and rigid, all steel and cast iron. Maybe 2 to 3 horsepower and a large and solid carriage with very long cross travel. No CNC at present and no threading. Electric drives using servos with feedback for speed control so computer control is easily arranged.

    This isn't going to be a showpiece build, just a very functional machine that I am putting together entirely from materials on hand, mostly scrap and recycled parts with the possible exception of a motor and VFD.

    One of the reasons for the short center distance is portability. I need to keep the weight of the bed down to something that can be moved by two people without equipment so it may not weigh more than 150 lbs or so (just the bed). Same for the headstock and tailstock as well as the main drive. Further details are to be worked out as the build progresses. This is a design as I go project although I already have nearly all the elements worked out in my head.

    I decided to make the most difficult and most critical part first, the spindle. I used a large chunk of 300 series stainless steel I had laying around. It was cleaned up and the required bearing seats and spindle nose threads laid on. It is designed to be able to use my chucks from the SB so it has a 1 1/2" x 8tpi nose. The next step was the hard one, boring out a little over 12 inches of somewhat work hardened stainless steel.

    It will have a through spindle capacity of 1 inch. That is the most the nose diameter can accomodate and still also accomodate a #4 morse taper. I am using MT4 with a sleeve to make it possible to use my existing tooling.

    The spindle bearings are some that were given to me by a board member, Tryp, when he moved back east. He is also the person who gave me my Whipp 16 Shaper.

    The main spindle bearing is a SKF 5310 CZZG twin row angular contact bearing with an RPM rating of about 6000 and a dynamic radial load capacity of 10 tons, axial capacity of 8 tons. ID is 5 cm and OD is 11cm. The spindle tail bearing is similar but only single row.

    Here are some pictures. Fortunately for the boring operation I have a very good quality set of Sheffield Steel drill bits that are up to the job of drilling hard SS. Still, it wasn't easy with the job requiring proceeding in small stages. First a pilot hole is drilled on center and then a hole is driven a couple of inches with a 1/2" bit. Then that is enlarged to 3/4" to provide chip relief and the half inch is used again for another couple of inches. Then the 1" bit is used to provide chip relief for the 3/4" bit and the 3/4" is then used to drill the additional 2 inches following the lead of the 1/2" bit. This sequence is repeated until the 1" bit is the only remaining bit with enough reach and it is then powered through as far as it will go with the preceeding bore to maintain alignment.

    The spindle is reversed and the same operations performed. In this case I left the nose portion bored only to 3/4" to allow for laying in the correct taper once the lathe is operational.

    Total drilling time to get from the top image to the bottom image about six hours.










    I will be posting more images in this thread as I complete the rest of the parts for the rear spindle bearing and drive.
    Free software for calculating bolt circles and similar: Click Here

  • #2
    WOOT!
    That looks like... T3h ub3r spindlezzzorrz (MY PERSONAL LIFE IS NOT ON TRIAL!)

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    • #3
      Why do you have the bearing mounted while working on the spindle?

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      • #4
        Hi Evan.

        That looks like a great (and ambitious) project. I have some novice questions.

        Why are you machining it with the spindle bearing in place? Is it a press-fit on the shaft and you don't want to risk damaging it by pressing it off?

        Since you are building the entire lathe, why not make the shaft and leave the spindle end blank, then machine the nose thread & taper with the machine assembled?

        Looking forward to seeing this project come to fruition - please update as often as possible.
        Peter - novice home machinist, modern motorcycle enthusiast.

        Denford Viceroy 280 Synchro (11 x 24)
        Herbert 0V adapted to R8 by 'Sir John'.
        Monarch 10EE 1942

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        • #5
          Didn't GW Ewan* IIRC post one he built a couple, three years back. Pretty good swing with screw cutting capabilities?

          * Seeing as how the adnim has disabled the members list I think that is the name.
          Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.

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          • #6
            Evan,
            Very nice work on the spindle. Now that is quite a bearing!

            I will be looking forward to your future posts on this project.

            Steve

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            • #7
              Your quickest way in would be riser blocks....... but for 16" you would need about 3" or so. Might be a bit large for your bed.

              If you could live with 12 to 14" your blocks would be more reasonable.

              I fully understand the approach you are using, since you may be in somewhat of a machine desert, at least for usable ones. When the local shops get done with one, I suspect there isn't much left..........
              1601

              Keep eye on ball.
              Hashim Khan

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              • #8
                Wow, that is some bearing. I am really looking forward to this thread. I hope all the nay sayers, high jackers, back seat drivers, .... stay out of this thread and let it stay on topic. Building a tool with your own ideas, design, and with what you have at hand is very much in the tradition of Maudslay, Whitworth, and other original concept types.

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                • #9
                  Only thing I can see that matters is that double row bearing is a preset and non adjustable.

                  .
                  .

                  Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                  • #10
                    That bearing is intended to be a very tight press fit. I made the bearing seat wider than the bearing with a few tenths of a taper to help start it on. Once in place the bearing doesn't sit on the taper. I tried it for fit and it worked great. Too great. I didn't want to press it back off and there was no reason to do so so I left it in place.

                    Since you are building the entire lathe, why not make the shaft and leave the spindle end blank, then machine the nose thread & taper with the machine assembled?
                    The machine won't have threading capability, at least not to start with.

                    I already have two machines that can do threads. This lathe will be outfitted for computer control at some time in the future. That will also include spindle positioning, not just spindle encoding.
                    Last edited by Evan; 01-01-2009, 06:06 PM.
                    Free software for calculating bolt circles and similar: Click Here

                    Comment


                    • #11
                      "I need to keep the weight of the bed down to something that can be moved by two people without equipment so it may not weigh more than 150 lbs or so (just the bed)."

                      Oh come on Evan, you of all people should be able to figure out how to move a 1000 pound lathe around you shop all by your self. A friend and I put my 2000 pound LeBlond in my basement in about an hour with out any death or injuries. Gary P. Hansen
                      In memory of Marine Engineer Paul Miller who gave his life for his country 7-19-2010 Helmand Province, Afghanistan. Freedom is not free, it is paid for with blood.

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                      • #12
                        Only thing I can see that matters is that double row bearing is a preset and non adjustable.
                        This bearing is what is known as a Conrad style construction. The contact angles diverge from center instead of converging. According to SKF it can be preloaded in either direction and this style with diverging contact angles gives it high rigidity.
                        Free software for calculating bolt circles and similar: Click Here

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                        • #13
                          Thanks Evan yeah I should have spotted that - you did put it in the original post *embarassed*.
                          Peter - novice home machinist, modern motorcycle enthusiast.

                          Denford Viceroy 280 Synchro (11 x 24)
                          Herbert 0V adapted to R8 by 'Sir John'.
                          Monarch 10EE 1942

                          Comment


                          • #14
                            Evan I make lathes all the time and I wonder why you chose SS for material for the spindle I always thought that SS expands more with heat and can cause problems if your bearing gets hot or warm and I would be affraid for one of those days when the SS thread will grip to a Chuck back plate and cause big problem, Here is an example of a 32 inch lathe that I made


                            [/IMG]

                            Good luck with your built
                            Bazz

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                            • #15
                              I had always thought (and New Departure helped me think it) "conrad" bearings were the traditional groove types...... Which might not be the best type.

                              I am glad you mentioned preload.......

                              OLD type New Departure double row were available in zero clearance preloaded versions. The preload was established inside the bearing as manufactured.

                              Logan used that style for their early machines, with no external preload system. If you ever replaced the bearings, that type is no longer made* and you would get a bearing (as I did FROM Logan) that is chattery and almost useless.**

                              The cure is to retrofit preload for the nasty thing, at which point it becomes very usable and perfectly OK. That isn't necessarily easy on an existing design, but if you are scratch building it's not an issue.

                              Logan changed to an externally preloaded system pretty fast. The new system uses large belleville spring washers inside the headstock.

                              When you say "diverging angle", exactly what do you mean? There are two ways the angle could 'diverge".....

                              The most rigid, again per N-D, is to have the lines of pressure converge outside the outer race, which makes the "pressure diamond" wide along the shaft. The balls contact the inner race near the bearing faces, and contact the outer race near its middle.


                              * at least not made for sale unless ordered at high cost and minimum orders.

                              ** the clearance was almost 0.0013 for the bearing I had. Preload with belleville washers and an extra bearing fixed it.
                              1601

                              Keep eye on ball.
                              Hashim Khan

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