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  • Expanding Mandrels

    I am looking for any input on locating a reasonably priced set of expanding mandrels for lathe work. I am looking for the type that are held between centers, and vary in size from 1/2" to 2". Thanks!
    Arbo & Thor (The Junkyard Dog)

  • #2
    Expanding mandrels? They're not very accurate, they don't hold well, and their closest proximity ro accurate holding is near their minimum size.

    As expanding mandrels expand they go hour-glass shaped meaning they grip the work on the corners of the bore. The work has to be manually centered for grip as the tapered part of the mandrel is thrust in. If you sock it home the waist of the hour class deforms and holds moderately well provided any thrust is in the direction of hold.

    Expanding mandrels are convenient but I'd never trust them for accurate work or work on which I had to do much machineint. I'd rather make a spud expanded with a screwed in pipe plug as time consuming and expansive as that is than trust an expanding mandrel.

    The last time I saw expanding mandreals used in a production setting was for aligning, spacing, and welding on water tight door inges.

    On the other hand I'd love a set of chilled iron solid mandrels by 1/16" from 3/8" to 2 1/2". Fat chance. They were expensive even back when they were used a lot.

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    • #3
      I just always use a temporary self locking mandrel, better accuracy. Are you aware how to make one?
      Michael

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      • #4
        I have a fair assortment of KO Lee expanding mandrels that are held between centers.

        They aren't cheap.

        I use them for tool grinding, among other uses. I believe they're quite accurate over their complete range of expansion, I'm sure they're well with .001" TIR.

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        • #5
          The story is, this guy is hot-rodding a big F-250 for pulling competition. He is fabbing up some sort of dual clutch system. What is happening...the mounting hub in the clutch plate gets removed. Chuck it in the lathe, and removed splined hub area from the center. Then, weld in a larger splined hub. Then, return to the lathe...hopefully mounting said splined hub on some type of arbor or mandrel mounted between centers, and taking a truing cut on all outside surfaces. The clutch plate and hub assembly will then be reassembled together, and installed in the truck. The only part I have in this is the actual welding and machining. Another experienced machinist friend told me that an expanding mandrel would be the way to go. I have never used one, but it sounded promising to me. If I could get a piece of the splined shaft, that would work with some locking collars, but the customer tells me that isn't possible. Any other ideas to mount this thing up for a truing cut would be appreciated. The way I see it, I need to count on the ID splines to ensure concentrcity on the OD of the part.
          Arbo & Thor (The Junkyard Dog)

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          • #6
            This set doesn't reach 2" but is it what you had in mind?
            http://cgi.ebay.com/Lathe-expanding-...QQcmdZViewItem
            I think Enco has a set up to 2" but it's around $500

            [This message has been edited by johnc (edited 07-15-2005).]

            [This message has been edited by johnc (edited 07-15-2005).]

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            • #7
              Make your self an alignment shaft out of bar stock. Turn piece to fit snugly in hole in clutch hub .. If a spline is needed mill a couple ok slots in your shaft then make a key to fit the hub Jim
              jim

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              • #8
                It would be better to build/machine a fixture to hold averything in location as you weld it.

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                • #9
                  Forrest,

                  <font face="Verdana, Arial" size="2">Expanding mandrels? They're not very accurate, they don't hold well, and their closest proximity ro accurate holding is near their minimum size.</font>
                  Does that include the KO Lee mandrels? Probably so, but they seem to bring enough on Ebay that I always figured they had to be pretty good.

                  Mike
                  Mike Henry near Chicago

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                  • #10
                    http://www.kolee.com/mandrels.htm

                    These are accurate and grip parallel. They are not for heavy cuts, but will serve the purpose when used properly. I think they are more suitable to grinding than lathe work.

                    They are expensive. It is usually easy enough to make a dedicated expanding arbor for the job at hand. It will be just as accurate, or better. The price is right, and you will have it in 15 minutes.
                    Jim H.

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                    • #11
                      I use expanding mandrels as a last resort,if all you need is+- .001" they are fine.

                      Usually what I di is chuck up a piece of barstock larger than the bore in the part and machine a 45 or 60 cone on it to fit in the bore,then just put the part between centers using a pipe or bullnose center.Tailstock pressure provides enough friction to machine the od of the part so long as light passes are made.
                      If the ends of the workpiece are true(the clutch hub most likely will be)it will work fine.
                      I just need one more tool,just one!

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                      • #12
                        I use expanding mandrels quite often, They are good for.001-+, they have to be taken care of, I see people toss them around all the time like the were and old piece of bar stock, they do the same thing with centers, files and reamers.
                        Non, je ne regrette rien.

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                        • #13
                          How about making a tapered mandrel? .006 inch per foot taper turned between centers to fit the part you need to turn.
                          THAT OLD GANG 'O MINE

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                          • #14
                            Thanks - I picked up a set of 3 nice ones at auction a few years back for $25 or so. I don't need them very often and was wondering if they should be Ebayed. Sounds like it's better to keep them.

                            Mike

                            Mike Henry near Chicago

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                            • #15
                              I recently bought a set of 5 expanding mandrels ranging in size from 1/2" to 1" from Wholesale Tool for $89.

                              They are well made and appear to be excellent materials. I often have some in between size to work with that my regular madrels can't handle. So instead of filling up the place with every size I got the expanding ones not expecting them to be much good. Surprise. They work just fine and I wish I had bought them earlier.

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