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ER Collet for lathe use on short parts?

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  • ER Collet for lathe use on short parts?

    Hello,

    I've dived into using an ER40 collet set on my home lathe to hold parts (logan 210). It works very well for pieces that are long enough to go into the collet a fair ways, but short pieces don't really work.

    In alot of ways I'm kicking myself for not spending that money on a 5C collet chuck, but I digress....

    Basically I've run into the problem where you try to hold a part feature that is short and the collet doesn't tighten up right. I've put plugs inside the back of the collet that match my work piece but unless you have plugs for every size you plan to machine I don't think this is even a good approach. I don't want to buy $800 worth of gage pins for every size from 0.120"-1.000" just to justify my $150 ER40 collet set!

    Does anyone know of an adjustable plug that you can make fit your part (maybe a short expanding arbor or something?). Any other tricks to using these collets?

    Thank you,
    KEJR

  • #2
    You could start by not abusing the collet set you bought and try something intended for work holding.

    Comment


    • #3
      Can't say as I have run into this problem....I make sure that there is enough stock sticking into the collet to reach past the gripping area.

      I can see where it would be a problem though for second-op work where the stick-out on the piece is short...the ER collet doesn't clamp evenly. Unfortunately, the only way to get it to clamp evenly is by introducing a spacer at the back of the clamping surface...just as you are doing.

      Just had a thought...
      If your collet chuck attaches to your spindle without a drawbar, maybe you can measure the distance from the left-end of your spindle to the back of the collet. Now cut a length of stock turned to the desired diameter and 1/2" longer than the measurement. Insert it from the left-end of the spindle into the collet. That should make it easier to handle than trying to deal with a small plug that might (will??) fall out of the collet each time you loosen the nut. Of course, you will still have to make a new piece every time you are dealing with a new diameter. Not sure how you would get around that one....

      Andrew

      Comment


      • #4
        Soft jaws

        Originally posted by KEJR
        Hello,

        I've dived into using an ER40 collet set on my home lathe to hold parts (logan 210). It works very well for pieces that are long enough to go into the collet a fair ways, but short pieces don't really work.

        In alot of ways I'm kicking myself for not spending that money on a 5C collet chuck, but I digress....

        Basically I've run into the problem where you try to hold a part feature that is short and the collet doesn't tighten up right. I've put plugs inside the back of the collet that match my work piece but unless you have plugs for every size you plan to machine I don't think this is even a good approach. I don't want to buy $800 worth of gage pins for every size from 0.120"-1.000" just to justify my $150 ER40 collet set!

        Does anyone know of an adjustable plug that you can make fit your part (maybe a short expanding arbor or something?). Any other tricks to using these collets?

        Thank you,
        KEJR
        Too or very short stuff is potentially a problem for any collet - and any chuck.

        The best solution is soft jaws on a 3-jaw chuck.

        Comment


        • #5
          Simple solution: just cut another 1/2" of stock off after turning to the diamiter of your work. make plugs as needed.
          Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

          Comment


          • #6
            Originally posted by Black_Moons
            Simple solution: just cut another 1/2" of stock off after turning to the diamiter of your work. make plugs as needed.
            Thats what I do, but make it like a top hat & use blu tac to stop it dropping out.
            store them in a block of polystyrene (write the size on).
            john
            John

            I used to be indecisive. Now I'm not so sure , but I'm not a complete idiot - some bits are still missing

            Comment


            • #7
              A ER collet isn't intended for that kind of abuse.
              They work perfect as long as the material sticking inside is at least as long as the collet.
              Collets that are only half slit (only from one side) work better.
              But for short parts, collets like these were invented. Maybe you call them stepped collets, I don't know. They are not so easy to get.


              HTH,
              Nick

              Comment


              • #8
                Hardinge?

                Thanks Nick.

                Here is the Google translation German >English of that link:
                http://translate.google.com/translat...ft&sl=de&tl=en

                So far as I am aware, those collets are available from Hardinge and "Royal" (Sp?) and would be for R8 or C5 perhqaps - and MT? I don't recall seeing them in ER collets.

                Comment


                • #9
                  As has been mentioned, get a work holding collet.

                  The 5C is the most common, although the Logan spindle probably is not large enough to have the collet inside the spindle like it should.

                  The ER collet as a work holder is mostly a "hobby" thing. I don't recall ever seeing them used this way until recent years. And, never in production shops.

                  Comment


                  • #10
                    Originally posted by MuellerNick
                    A ER collet isn't intended for that kind of abuse.
                    They work perfect as long as the material sticking inside is at least as long as the collet.
                    Collets that are only half slit (only from one side) work better.
                    But for short parts, collets like these were invented. Maybe you call them stepped collets, I don't know. They are not so easy to get.


                    HTH,
                    Nick
                    Agreed BUT In a jobbing shop, where you may be doing only 1 or 10 off, if you havent got a 5c that size but an ER that fits..... Collets should be treated as disposable items & replaced when worn.
                    John

                    I used to be indecisive. Now I'm not so sure , but I'm not a complete idiot - some bits are still missing

                    Comment


                    • #11
                      Originally posted by jugs
                      Agreed BUT In a jobbing shop, where you may be doing only 1 or 10 off, if you havent got a 5c that size but an ER that fits..... Collets should be treated as disposable items & replaced when worn.
                      The way I do it is using 5C emergency collets bored to size. We are a job shop.

                      Over the years I've accumulated probably a hundred or more soft collets. When an odd size or short part comes in we bore the collet to fit.

                      Start with small parts on a new collet. As other jobs come in over time we keep boring it larger and larger until it's used up. For the fairly expensive Hardinge soft step chuck collets (2" and up in size) I've been known to weld in inserts to reuse the collet.

                      Comment


                      • #12
                        Pot chucks?

                        Originally posted by oldtiffie
                        Here is the Google translation German >English of that link:
                        http://translate.google.com/translat...ft&sl=de&tl=en
                        Sometimes (most of the time with technical language) Google translate is NOT your friend .

                        Stufenspannzangen = stage riser clamps? I think not!

                        I believe these are called pot chucks in English. Yes?


                        .
                        Thomas

                        Problems worthy of attack prove their worth by hitting back
                        - Piet Hein

                        Comment


                        • #13
                          Translation

                          Thanks Thomas - points noted.

                          But as I don't have a clue about any language other than English any usable translation is better than none - mostly - as I can usually work it out from the context once I 've got a usable start.

                          I can even make a lot of sense from "Chingalish" - at last - but it took a lot of time, effort, frustration and heart-ache.

                          After that effort "Google" translation looks pretty handy to me.

                          Comment


                          • #14
                            Soft jaws

                            All or any of these "pot chucks" (thanks Thomas) are OK if and only if you have the adaptor for them on your lathe.

                            I can't see why soft-jaws on a 3-jaw chuck are not considered as a good solution. If you have a 3-jaw chuck that can take soft jaws you have all that you need. Making or buying the soft jaws is quite feasible and very practical.

                            Further, you can leave the job in the soft jaws and remove the chuck from the lathe to the mill and back again if needs be. Most "pot" collets don't have that portability.

                            Comment


                            • #15
                              DIY Pot Chucks

                              Like KEJR, I got an ER collet set but in my case it is used for long items where the stock protrudes into the spindle. The answers in this thread indicate using ER's for short items may not be the easiest approach.

                              To hold short items I make pot chucks to fit into my 3 jaw chuck, basically split sleeves with a shoulder on the outer end for alignment. If marked so their orientation vs the jaws can be repeated they typically have about 1 thou runout. It takes a little time to make them but I am slowly building a small collection so I do get to re-use them occasionally.

                              See: http://www.gadgetbuilder.com/MiniMods.html#PotChuck
                              The examples shown are for very short items but I now have some for longer items with smaller diameter - works well for them too although there is a lower limit dictated by the thickness of the slitting saw.

                              John
                              Location: Newtown, CT USA

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