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  • Want to make a collet chuck...

    I plan on making a collet chuck for my lathe and I'm trying to decide whether to go with ER 32 or ER 40 collets. ER 32 goes to 3/4" while ER 40 goes to 1" and I'm wondering how often I'd actually need the extra size and what others think.

    My lathe came with a decent (Chinese) 8" 3-jaw and a 10" 4-jaw and I'm thinking that for precision work over 3/4" a high quality 3-jaw--probably with soft jaws--would do the trick. One that size won't be that expensive, should provide pretty good accuracy for the 3/4" to 1-1/2 " range. Still, there may be times when it will be nice to be able to throw something up to 1" in a collet. I've thought about this for too long and now I can't make up my mind...
    Keith
    __________________________
    Just one project too many--that's what finally got him...

  • #2
    I would suggest 5C collets instead, as ER collets will need material all the way through the collet length so that it will grip it properly and not collapse. Other option is to put some scrap piece the same diameter than the workpiece is inside the ER collet if the workpiece is shorter than the collet.

    If you want to go ER route, go with the bigger or if you have a mill, go with the set you would/could use on the mill also to save some money
    Amount of experience is in direct proportion to the value of broken equipment.

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    • #3
      5C collets may need a draw-bar though the head-stock spindle - depending on what collet holding system you use - and the hole through the draw bar will be less than that in the spindle.

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      • #4
        You need far less collets with an ER system to cover ALL sizes.
        ER's have a gripping range of 1mm or 40 thou.

        5C's are more limited.
        .

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



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        • #5
          For a lathe I would go with the ER40.
          John has a lot more experience with collets than me, but I agree with him about the 5C collets, you need a lot of collets to cover the range both in imperial and metric, but they do have the advantage of holding square and hex shapes as well as having emergency collets available.

          A lot of stores like CDCO are now selling a Er 32 or 40 collet chuck already mounted to a back plate to go onto lathes and are cheap. So it's only a matter of finding a back plate to suit your lathe to mount it.

          Another way is to make your own by buying a MT3-4 collet chuck, cutting the back end off it and press fitting it into a back plate yourself, either direct mount of back plate mounted to the lathe. This is a cheap way to go when you look at buying a collet chuck from say CTC tools in China for around $20 US, and then you have the advantage of it being hardened and ground.
          A lot of people have gone this way, and if it's back plate mounted you have the option of fixing any run out by aligning it before doing up the bolts.

          I only have a MT mount one which is a pain as you cant pass anything though the headstock like the others, but then again I am not doing production runs and it's rarely used.

          Dave

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          • #6
            Originally posted by John Stevenson
            5C's are more limited.
            Originally posted by Jaakko Fagerlund
            I would suggest 5C collets instead,
            each has their advantages/disadvantages, really you need to make two chucks . I've ended up with sets of rubber flex and 2J or 5C collet chucks for each of my lathes as there are times when one does out perform the other.

            Another difference is that with the 2J (or 5c style) you can cut right up to the collet. This is a frustrating limitation of collets needing nose cap style closers when doing very small work. If I only had one it would be 5c; you need more collets, but they there are less limitations. There are also things like pot collets and mandrels are readily available.

            end of the day though, they both accomplish 98% of what someone wants from a collet system - holding things concentric to a high degree of accuracy. So, ease of making it would be a big consideration in which to chose.

            There is a very nice collet chuck build at practical machinist: http://www.practicalmachinist.com/vb...jogren-159842/
            .

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            • #7
              Originally posted by Jaakko Fagerlund
              I would suggest 5C collets instead, as ER collets will need material all the way through the collet length so that it will grip it properly and not collapse. Other option is to put some scrap piece the same diameter than the workpiece is inside the ER collet if the workpiece is shorter than the collet.
              How serious a problem is this? What would be the minimum length of material that an ER collet could effectively hold for, say, 1/4" dia? 1/2"? 3/4"? Would 2x dia. be sufficient or will this vary with material size?

              Given a choice I'd prefer the ER system to the 5C, mainly because the ER opens from the front. As has been mentioned a 5C setup would require some sort of drawbar to operate.

              If you want to go ER route, go with the bigger or if you have a mill, go with the set you would/could use on the mill also to save some money
              A good point also. My mill has a BT 30 taper and uses an OZ 25 collet holder system but it would be handy to have both the lathe and mill using the same collets...
              Keith
              __________________________
              Just one project too many--that's what finally got him...

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              • #8
                Originally posted by LKeithR
                How serious a problem is this? What would be the minimum length of material that an ER collet could effectively hold for, say, 1/4" dia? 1/2"? 3/4"? Would 2x dia. be sufficient or will this vary with material size?
                If the collet collapses, it grips only from the very front end of the collet only and will simply not hold. I can't say how much is minimum, but I can say that recommended is the length of the collet.

                If you put a shorter than collet workpiece, first push the same diameter scrap piece to the back side of the collet. This way the collet won't collapse and you get nice and even crimping force on your workpiece. In this instance the minimum workpiece length is about anything that gets enough holding power from the collet to stay put under cutting forces and as you might guess, it depends on your material, cutter, etc. I would however recommend about one diameter length, but again, this is not carved in stone.
                Amount of experience is in direct proportion to the value of broken equipment.

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