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Why is it so hard to get a centered 5C collet?

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  • Why is it so hard to get a centered 5C collet?

    A middle of the road brand like Lyndex has a TIR spec of 1.1 thou. (I have measured a few, and they are pretty good about giving you exactly that.) A fancy pants brand like Hardinge is only .5 thou. The super fancy pants "special accuracy" collets from them have .2 thou. I thought 5C was supposed to be the epitome of "don't worry, it'll be concentric" type of work. Don't you just grind the inside and outside of the collets? The spindle taper on the cheapo chinese lathe I use is PERFECT (as measured by me) so it would be a shame to ruin it with a collet.

  • #2
    Remember that "perfect" is a moving target. Temperature, material, usage, and finally limits of metrology all play a role. Repeatability to a thou isn't to be sneezed at. Strive for perfection, but don't be a slave to it. My .02.

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    • #3
      I don't think so my as it is supposed to be perfect in runout, but perfect in repeatability. And it is still going to be just as good as the chuck you have unless you have something with the taper built in like a HLV. And that is still way better than a 3 jaw and won't mess up work.

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      • #4
        I have two sets of metric C5 collets that came with my Chinese) Tool & Cutter grinders.

        There is neglible run-out/TIR when used in the T&G grinder work-heads.









        That's all I use C5 collets for as I pretty well universally use ER-32 collets for everything else.

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        • #5
          If you must have "perfect" collets buy some "emergency" or soft collets and machine the ID in your lathe. They should then be as true as possible to your machine.

          However, as previously stated .001" TIR is more than acceptable for the vast majority of work. If it must be closer, work between centers or use a four jaw and dial it in to within a "wiggle".

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          • #6
            Originally posted by beanbag
            A middle of the road brand like Lyndex has a TIR spec of 1.1 thou. (I have measured a few, and they are pretty good about giving you exactly that.) A fancy pants brand like Hardinge is only .5 thou. The super fancy pants "special accuracy" collets from them have .2 thou. I thought 5C was supposed to be the epitome of "don't worry, it'll be concentric" type of work. Don't you just grind the inside and outside of the collets? The spindle taper on the cheapo chinese lathe I use is PERFECT (as measured by me) so it would be a shame to ruin it with a collet.
            What are you using the 5C collet for or in?

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            • #7
              The spec is just the maximum runout. I have cheap chinese/taiwanese ER-32 collets here, they said 0.01 mm TIR but have found that only in 2 of a whole set, the others less than that.

              So I would not perhaps worry that much and if you truly need the precision, buy the more tightly spec'd collets
              Amount of experience is in direct proportion to the value of broken equipment.

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              • #8
                Originally posted by beanbag
                A middle of the road brand like Lyndex has a TIR spec of 1.1 thou. (I have measured a few, and they are pretty good about giving you exactly that.) A fancy pants brand like Hardinge is only .5 thou. The super fancy pants "special accuracy" collets from them have .2 thou. I thought 5C was supposed to be the epitome of "don't worry, it'll be concentric" type of work. Don't you just grind the inside and outside of the collets? The spindle taper on the cheapo chinese lathe I use is PERFECT (as measured by me) so it would be a shame to ruin it with a collet.
                Like all tooling, you get what you pay for !

                There is no "Perfect" in manufactured components. !
                Better is more $$$$

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                • #9
                  Originally posted by oldtiffie
                  What are you using the 5C collet for or in?
                  Trying to measure the runout on my ER16 collet chuck.

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                  • #10
                    Originally posted by beanbag
                    Trying to measure the runout on my ER16 collet chuck.
                    Eh..if I didn't miss anything, you check that by measuring the chucks taper/bore, not the collet. If you measure collet when installed, you are actually measuring the combined TIR of the chuck, the collet and whatever is in that collet.
                    Amount of experience is in direct proportion to the value of broken equipment.

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                    • #11
                      +1

                      I rather got the same impression as Jaakko Fagerlund.

                      Using one collet adaptor as a reference to check another is hardly the way to go to get the required result if the reference itself is questionable on at least two or three levels.

                      Just to clarify the issue, can the OP post a pic of the set-up please.

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                      • #12
                        FWIW, Hardinge 6K collets in my South Bend 10K have a tenth or less measured runout indicating off a dowel pin.
                        ----------
                        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.
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                        • #13
                          Originally posted by SGW
                          FWIW, Hardinge 6K collets in my South Bend 10K have a tenth or less measured runout indicating off a dowel pin.
                          Sounds about right....

                          if you can't get any better than a thou with collets, you are as well off to use a 3 jaw chuck as a collet.

                          That said, using a collet in a closer in the taper of a spindle is adding up several tolerances.

                          Using a collet in a collet chuck screwed onto a spindle is even more tolerances added. Same for a cam lock or other "real" spindle system as well. If your machine takes the collet in the spindle directly, you should do better than in a closer or chuck.

                          While I agree that measuring stock held in a collet adds more tolerance, if you check with a good ground pin in a collet that is in a taper socket made as part of the spindle, the resulting measurement is going to reflect about the best you can do with that collet in that machine. After all, they ARE intended to actually HOLD a part, and the *holding* is what is supposed to be concentric and true.
                          1601

                          Keep eye on ball.
                          Hashim Khan

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                          • #14
                            Originally posted by Jaakko Fagerlund
                            Eh..if I didn't miss anything, you check that by measuring the chucks taper/bore, not the collet. If you measure collet when installed, you are actually measuring the combined TIR of the chuck, the collet and whatever is in that collet.
                            The er collet chuck is 3/4 shank on one end and ER16 on the other. What am I supposed to use to hold the shank and spin it?

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                            • #15
                              My experience with Lyndex 5C collets (I bought a full set) is that they had worse run out than the cheapo chinese ones and on top of that some of the threads were out of spec.

                              I ended up sending the Lyndex set back and getting a chinese set but I bought individual Hardinge ones for the sizes I use often.

                              There is one other US manufacture that still makes 5C and R8 collets but there name escapes me right now, it will probably pop in my head later and I'll post it back.

                              Paul T.
                              www.power-t.com

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