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Position of the endmill

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  • Position of the endmill

    I normally use an endmill holder for endmills with weldon shank but for others I use a collet. With the Weldon shank, the depth with which the endmill is inserted is automatically adjusted by the flat spot, however when the endmill is held by the collet there's more flexibility. So, the question is, when the endmill is held by a collet can you insert it deeper to get more rigidity, or should the entire fluted portion of the endmill always be exposed (will that damaged the collet?) ? As always, thanks for your many good advices.


  • #2
    Since the bearing surface inside a collet is relatively short, I wouldn't recommend having anything other than solid shank held by a collet. Except for end mills that happen to be the o.d. of the shank (3/16", 3/8", or whatever), the flutes wouldn't contact the collet (e.g. 5/16" end mill with 3/8" shank), or they wouldn't fit (e.g. 7/16" end mill with 3/8" shank).

    If your setup isn't rigid enough, think about getting a stub end mill...or taking lighter cuts.
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    • #3
      Collets are the best holders when it comes to concentricity...the weldon shanks, when used with a set screw, are not as concentric, but they are much more rigid...Only hold on to the smooth shank....The flutes, whether it be a drill or endmill, shoould never be held onto...



      • #4
        Be very careful when using an end mill in a collet if you are making a deep cut. The spiral on the flutes can pull the end mill out of the collet and cause all kinds of trouble.


        • #5
          I have had end mills come out of my collets. Is that usually because of my cuts being too deep? Is my end mill turning to slow? Fast? Just curious as to what some of the causes are for this?


          • #6

            If you have an ER collet system and have a plain steel nut get a Ball Bearing Nut - it allows greater tightening torque than a plain nut. HSS endmills tend to pull out less than solid carbide endmills or drills do.

            TG style collets are better than the ER type.

            Hydraulic collet chucks offered the highest clamping pressures and best high speed balance prior to the development of the shrink systems.

            The best endmill holders out now are the shrink systems for the NT40 and larger tapers. The metal of the toolholder is heated with RF and it expands enough to insert the endmill and preset it. It is then allowed to cool and the toolholder shrinks around the endmill shank in a death grip. This is as close to a one piece tool at a reasonable price we have come.


            • #7

              can you please explain what ER and TG is? Have never heard of these.

              Apart from R8, have only used Clarkson collet system. These seem very common here. The cutter is screwed in to the collet, then the collet nut tightened. The cutter will not move.

              Rotate, for normal milling, I would not put flutes up into the collet, I can't really say why, just habit? May be hard on collet and cutting edges of cutter? You can get cutters with different flute lengths. You are not trying to use Long series cutters for normal milling are you?


              • #8
                Peter S:
                ER collets are a self releasing (when used with a Ball Bearing Nut) double angle precision collets. TG is a heavy duty (around 7* angle?) collet that grip with enormous force - they can leave collet marks on the shanks of crappy tools.

                If you would like to see the various types check out - they also have the shrink system on that site.

                I considered the Clarkson Milling chuck but found plain shank endmills are cheaper and easier to get (I can get what I want locally).

                [This message has been edited by Thrud (edited 06-09-2002).]


                • #9
                  I use colletts for milling. Concentricity and even flute wear. I use the holders as well, but not as often. They do have a big place in my shop though

                  The best way to hold an end mill in the collett is to have the flutes exposed all the way, 1/8" of the shank below the collett face. Rigidity is one factor. Another reason I have found directly is that chips follow the flutes up into the collet in some cases, gumming up the flutes, sticking in that wierd area, damaging the collett.

                  CCBW, MAH


                  • #10
                    I agree completely. And collets are not cheap.


                    • #11
                      To me it just makes no sense to get the flute up inside the collet, since collet jaws don't clamp on air very well. However, one of the guys I work with routinely chokes up on endmills more (ER collets), and I have to admit that we have less trouble with tool vibration that way, especially with 1/4 and 3/8" end mills. But I agree with spope that chips packing in there can be a problem.