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End mill holders vs ER collet

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  • End mill holders vs ER collet

    I'm referring to the holders that you slide an end mill into and secure with a set screw from the side. I've never trusted them much for runout, but I'm not sure how much that matters. I don't worry about the set screw too much when using HSS end mills, but I'm kind of worried that I will crack a carbide end mill.

    On the other hand, I had an end mill start to pull out of an ER collet when I thought I had it snugged down pretty reasonably.

    Both the end mill holder and ER collet are on 3/4" chucks that slide into a modified R8 collet. What are the pros and cons of each type of holder? Which is more rigid?

  • #2
    beanbag,
    Lots of variables, a good tool holder with a set screw will likely have less runout then a cheap collet holder with collet. Ultra High rpm machines I believe use collets almost exclusively.
    The set screw will not crack carbide cutters, that is a given.
    I put it like that so someone will argue the point

    Your set up will likely have more runout then a single R8 tool holder or a fixed R8 Collet holder.

    If you have good collets and holders, either, tightened properly should do you well.

    Comment


    • #3
      With the ERs cleanliness is VERY important, and you are SUPPOSED to lightly oil the tapers while making sure the endmill and ID of the collet are VERY clean and oil free. I'm guessing you are using ER32s? They take a butt of torque. ER40's are supposed to be tightened to something like 130 ft lbs. I'm not sure where the ER 32s are supposed to be, but I'm sure they aren't far behind.

      A quality set screw holder will have very little runout, and you aren't going to crush a carbide endmill, I can guarantee that. You may end with a bit more runout on an R-8 deal since you'll be hanging out there and any error will just be multiplied.

      I only use the ER's for finishing, with 3/8 and up, but use them exclusively for anything under 3/8".

      Comment


      • #4
        There are ball bearing nuts for ER 32/40 around that let you tighten them up easier, maybe give that a try. Here are a few on Ebay the 40's are not listed at the moment but usually are.

        http://cgi.ebay.com.au/OZ25-collet-c...item56379f87c4

        http://cgi.ebay.com.au/ER32-collet-c...item5637ba9074


        Also talk of them here, and a US supplier.
        http://www.candlepowerforums.com/vb/...d.php?t=251457

        Dave

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        • #5
          Woah 130 ft-lbs? No wonder people complain about the odd slip up.
          Any idea what kinda torque one should use on the drawbar when using R8 collets?
          Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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          • #6
            Originally posted by Black_Moons
            Woah 130 ft-lbs? No wonder people complain about the odd slip up.
            Any idea what kinda torque one should use on the drawbar when using R8 collets?
            Thats what I'm wondering, how are you guys running ER32,40s off an R-8 tightening 'em. An ER-16 doesn't take much, but those big collets, you have to wail on them.

            A few years ago when the first Cat40 machine showed up in the shop, I stuck a gage pin in an ER-40 holder(new collet, new holder good spindle) gave it a squeeze and was getting .0015 of runout, well indicated runout, I was pretty Maritool stuff, later that night I ran across a thread on the other board where Frank Mari was talking about proper torque on the collet nuts, went back out to the shop, took the same holder and collet, it was still in the machine, put it in the nice little Cat 40 holder that was bolted to the nice heavy bench and LEANED on it as hard as I could. Popped her back in. TIR was about 4/10 of the way between the lines on a .0001 indicator, so .00004, 40 millionths, not too bad. The went to

            Drawbar torque on an R-8, no idea, I always used a stubby half inch wrench so it could swing around 360, and just gave her a good yank, I'd pull out a real wrench if I was going to do some real milling, and I had a few tools pull out. I think if you had a light oil in your taper and on your threads and nice oil free and clean collet ID and endmill shank you should be pretty good. Somebody somewhere suggested a light scuff on the endmill shanks with some sandpaper, especially the really shiny carbide endmills.

            On the ball bearing collet nuts, I like the idea, but they seem to break pretty easy and its another place for crap to gather, since the balls move they supposedly can throw off the balance of the tool. And they cost more.

            Comment


            • #7
              Originally posted by beanbag
              I'm referring to the holders that you slide an end mill into and secure with a set screw from the side. I've never trusted them much for runout, but I'm not sure how much that matters. I don't worry about the set screw too much when using HSS end mills, but I'm kind of worried that I will crack a carbide end mill.

              On the other hand, I had an end mill start to pull out of an ER collet when I thought I had it snugged down pretty reasonably.

              Both the end mill holder and ER collet are on 3/4" chucks that slide into a modified R8 collet. What are the pros and cons of each type of holder? Which is more rigid?
              Set screw holders may have some inherent runout, though they may be rather tight fitting and slightly off center to reduce this. For small cutters, this matters a great deal but set screw holders are frequently used on larger cutters where slippage may be more of an issue. If you are making 0.010" chips, 0.001" of runout isn't such a big deal. On a 10mil diameter end mill, it may be the sound of broken carbide. I have seen posts to the effect that set screw collars were the only ones (out of a wide range of systems) that poster had not seen slip. Oh, I have one end mill that won't fit in the appropriate sized set screw holder short of resorting to shrink fit - it is about 0.0003" larger in diameter than the ones that fit. Not a huge amount of play there.

              ER collets want to be clean, clamped very tight, and with the shank more or less the full length of the collet since ER's clamp front and back. If your shank or work doesn't go to the back of the collet, you may need a same diameter plug back there. Otherwise, your collet deforms into a taper. Many other collet systems primarily clamp in the front which is better if you don't have much depth in collet but doesn't center the part angularly on axis so you may need to nudge it on axis before tightening fully. One random vendor recommends clamping torques of 21, 37, and 77 foot pounds for ER16M, ER16, and ER32, respectively.

              There are also shrink fit and collet chucks (very shallow taper collet backed up with needle bearings).

              On the set screw holder, you have the R8 fit, the 3/4" fit, and the end mill fit. On the ER, you have the R8 fit, the 3/4" fit, the ER outside taper fit, and the end mill fit. On an actual R8 collet or an R8 end mill holder, you would only have two fits instead of 3 or 4. More places to get runout, more places to slip.

              I lean towards collets for smaller end mills and set screw for larger ones but varies depending on the precision and torque required for the particular cut and what is available.

              You mileage could vary a bit from other peoples' based on differences between the fit and finish of the particular tooling you have and proper use or lack thereof and the circumstances of use. Do your own side by side tests.

              Comment


              • #8
                bobw53: Id really hope they are using a spanner (the proper spline type, Not some crecent wrench -_-) on the quill drive spline to provide that torque.. or a spanner on the ER32/40 collet chuck itself. (And not on the R8 drawbar)
                Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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                • #9
                  Originally posted by bobw53
                  Thats what I'm wondering, how are you guys running ER32,40s off an R-8 tightening 'em.
                  There's a big-assed monkey wrench that comes with the collet set. 130 ft-lbs sounds about right for ER-40, which is what I use on my R8 Excello.
                  "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                  • #10
                    you guys crack me up, only an anal homeshop machinist would know exactly how much torque ft-lbs he puts on his R-8.

                    I just tighten the fuggin thing and have never had an endmill pull out yet and I dont over tighten them either, I have seen guys rip the threaded portion of cheap R-8's right out of the collet by over tightening. That's always a fun repair getting the draw bar out.


                    okay I have had a few "pull out", but it was because I forgot to tighten the damn thing when I was sidetracked by something else.

                    Comment


                    • #11
                      Originally posted by mochinist
                      okay I have had a few "pull out", but it was because I forgot to tighten the damn thing when I was sidetracked by something else.
                      You mean I'm not the only one who's done that?

                      The only time I use EM holders is for extension to get past obstructions. Otherwise, it's just collets, and never a problem. No torque wrenches here either, at least not on collet draw bars.
                      Russ
                      Master Floor Sweeper

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                      • #12
                        Originally posted by lazlo
                        There's a big-assed monkey wrench that comes with the collet set. 130 ft-lbs sounds about right for ER-40, which is what I use on my R8 Excello.
                        I know that wondering how easy it is to get that much torque while the holder is in the spindle, or do the ER extensions have flats or a place for a second spanner?

                        Comment


                        • #13
                          Originally posted by bobw53
                          I know that wondering how easy it is to get that much torque while the holder is in the spindle
                          My point was that with the size of the spanner they give you, it's pretty easy -- it's a cinch tight plus a grunt Like tightening a bolt on a car tire. The ER-32's and especially the ER-16's are much easier to tighten.

                          I have the ETM ER collet sets, and they have the square spline teeth and a matchng spanner with spline teeth across 180°.

                          The Chinese sets have a hook spanner, even on the ER-40 sets. I don't know how well that works...
                          "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                          • #14
                            I looked up the torque spec of an ER40 collet: 146 ft lbs!!!!!! That requires you to really lean on a 2 ft breaker bar. My lug nuts only require 80 ft lbs.

                            Even for something dinky like an ER20 collet, the torque is 60 ft lbs. That is way beyond "snug".

                            Using this much torque may create enough clamping force to crush the outer electron shells of the end mill, causing it to collapse into a mini neutron star.

                            Comment


                            • #15
                              Messureing the torque you use on an R8 has one major benifit: the result can be transmited over the internet.
                              How tight is 'snug' 'really tight' 'striped' 'loose' 'kinda tight'. Nobody knows!
                              If you tighten your R8 with the normal wrench, then take your torque wrench and messure the exact point where it starts to tighten more, You can then tell others who can do the same and tell if they are using less or more torque by compairing the numbers. And then someone can 'learn' to feel just how 'tight' it should be, without using the torque wrench, because they now have a refrence they can compair to.

                              Im not saying use a torque wrench EVERY time, but use it so what you say actualy means something. 'Tight' is meaningless.
                              If more people read recommended bolt torque charts and used torque wrenchs as a learning aid insted of 'as that funny tool you might need for engine cylinder head bolts' we would have less striped nuts&bolts (and drawbars) in the world.
                              Last edited by Black_Moons; 12-10-2009, 05:04 PM.
                              Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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