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Why is my little ER16 Collet chuck an end mill breaker?

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  • Why is my little ER16 Collet chuck an end mill breaker?

    So I got one of those ER16 ER collet chucks on a 3/4" shank from CTC Tools. It appears to look ok, but when cutting, it seems to want to break 1/8 end mills more easily than usual. This is slotting mild steel.

    I checked the runout, and there is no more tool stickout from the collet face than usual. The only things that were kind of funny were:
    When tightening the collet nut, it feels really squeaky and creaky, despite being oiled.
    When tightened, the collet segments aren't always evenly spaced, for example, the gaps coming out radially from the end mill aren't even, and some are bigger than others.

    I broke an end mill after only cutting about 15 pieces, (end mill was still sharp and new-looking) while usually I can go 240+ pieces until the end mill wears out on my larger ER20 holders.

  • #2
    Is it flexing? Have you tried a quality collet?

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    • #3
      You probably already know, but are you putting the collet into the nut properly? You have to angle the collet and it sort of clicks in.

      Dave

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      • #4
        what does the 10th's indicator say? chuck something longer or extend the cutting tool a bit if the shank is long and indcate twice - close to the chuck and away....there could be misaligment beteen cutter and spindle axis, ie cutter isn't eccentric but moves in a cone patter...its always possible indicating in one spot could read zero...like a broken watch being right twice a day
        .

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        • #5
          Originally posted by Mcgyver
          what does the 10th's indicator say? chuck something longer or extend the cutting tool a bit if the shank is long and indcate twice - close to the chuck and away....there could be misaligment beteen cutter and spindle axis, ie cutter isn't eccentric but moves in a cone patter...its always possible indicating in one spot could read zero...like a broken watch being right twice a day
          Even a broken lathe has 0 runout twice a revolution!
          Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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          • #6
            Originally posted by beanbag
            The only things that were kind of funny were:
            When tightening the collet nut, it feels really squeaky and creaky, despite being oiled.
            When tightened, the collet segments aren't always evenly spaced, for example, the gaps coming out radially from the end mill aren't even, and some are bigger than others.
            If you've not already done it, check that the collet has been slotted correctly?

            FWIW I bought a 20mm shank by 150mm (6") long ER11 holder and collets from CTC recently for a project. The ER11 holder was held in my ER32 holder in the mill and I fully expected my 3mm end mill to go 'ping' immediately but it was good as gold.

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            • #7
              OK, I will try putting a longer object to see if the runout is the same in two places. And yes, I know how the nut on an ER collet works, and no, I doubt that the 3/4" collet holder is flexing relative to the 1/8" end mill.

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              • #8
                Sounds like the taper in the chuck is not corect for the collets. Or is out of round.
                Craftsman 101.07403
                Grizzly G0704
                4x6 Bandsaw

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                • #9
                  Originally posted by beanbag
                  So I got one of those ER16 ER collet chucks on a 3/4" shank from CTC Tools. It appears to look ok, but when cutting, it seems to want to break 1/8 end mills more easily than usual. This is slotting mild steel.

                  I checked the runout, and there is no more tool stickout from the collet face than usual. The only things that were kind of funny were:
                  When tightening the collet nut, it feels really squeaky and creaky, despite being oiled.
                  When tightened, the collet segments aren't always evenly spaced, for example, the gaps coming out radially from the end mill aren't even, and some are bigger than others.

                  I broke an end mill after only cutting about 15 pieces, (end mill was still sharp and new-looking) while usually I can go 240+ pieces until the end mill wears out on my larger ER20 holders.
                  As I understand it, it seems that your ER-16 adaptor shank is 3/4" held in collets either in another adaptor held in the collets either in the mill spindle of a seperate collet adaptor in the mill spindle.

                  If that's so it is a less than ideal set-up.

                  Comment


                  • #10
                    Originally posted by bob ward
                    If you've not already done it, check that the collet has been slotted correctly?

                    +1

                    I bought some cheap ER32 collets and found that the slits were not cut consistently. There was just a thin web at the end of about 1/4 of the cuts. This caused one side of the collet to get tight and other side did not. The endmill held in the collet was not centered.

                    I use a thin dremel cut-off disk and a thin saber-saw blade to make them all the same. Works great now. I found the same thing on several of the collets in that set.

                    Dan
                    At the end of the project, there is a profound difference between spare parts and extra parts.

                    Comment


                    • #11
                      Originally posted by bob ward
                      If you've not already done it, check that the collet has been slotted correctly?

                      FWIW I bought a 20mm shank by 150mm (6") long ER11 holder and collets from CTC recently for a project. The ER11 holder was held in my ER32 holder in the mill and I fully expected my 3mm end mill to go 'ping' immediately but it was good as gold.

                      First, Beanbag, you said you checked runout, but did you check it at two different distances from the collet face? The collet could be at an angle to the spindle axis and runout is OK near the collet but way off further out. Check runout as close to the collet face as you can and then check it 1-2 inches further out. Do this test on the same test piece without removing and remounting it.

                      Bob, re your two collet mount. You may have a good setup here or you may have a happy accident. Both of those collets and their mounts will have a certain amount of runout. These two runout figures can be in opposite directions and the net result will be a lower runout than either one individually. On the other hand, they can be in the same direction and add together to produce a greater runout than either one on it's own. This orientation will change in a random manner each time you use this setup. So don't be surprised if the results vary next time you use it.
                      Paul A.
                      SE Texas

                      Make it fit.
                      You can't win and there is a penalty for trying!

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                      • #12
                        I think that in general, if you look very closely at the rotating endmill and you don't see runout, then that isn't the problem. I would suspect that something is moving or flexing when the cutting edge hits the steel, and that would break endmills.

                        I would mount a piece of known round and smooth rod of the same diameter as the endmill shank. Have a good six inches or so of rod sticking out, and have the approximate length inside the collet that the endmill would have. Set up a dial indicator and check the runout first, and mark it if there is any. Then apply hand force against the rod and see what the indicator indicates. If the rod has more than one rest position, then it's not held securely in the holder.
                        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                        • #13
                          beanbag
                          make sure that your end mill shank is held both in the front and in the back of the collet.
                          Hilmar

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                          • #14
                            I have the same ER16 collet chuck that I use in a 3/4" side lock holder without any problems. This is a very handy little chuck for jobs where a bigger chuck would have clearance problems.

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                            • #15
                              I realise that this may sound a bit silly but have you checked for chips or other material in the slits of the collet as that can cause it not to close properly and could also cause runout .
                              I know as i put an ER32 in a holder without properly checking for clean and had to remove it and clean several chips out of it .
                              Michael

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