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Re: [mill_drill]Collets vs end mill holders

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  • Mario L Vitale
    Everyone who has made a comment on this subject has made a very good point. However, the discussion seems to indicate that it is a black or white issue. As
    Message 1 of 32 , Oct 5, 2005
      Everyone who has made a comment on this subject has made a very good
      point. However, the discussion seems to indicate that it is a "black or
      white" issue. As we all know, not very much in life is black or white.
      Let me just throw out a few thoughts that might help folks decide when
      they could or should use collets versus end mill holders.
      As someone already mentioned, end mill holders do have a positive means
      of retaining the end mill ... a set screw in combination with the relief on
      the shank of the end mill. The collet depends solely on friction.
      Two things that cause an end mill to pull out of a holder are high axial
      loads (higher than the interference the collet produces) and vibration.
      High axial loads are caused by large (>1/2"dia.?) and very heavy cuts (high
      chip load).
      Vibration is caused by, well, ....ah, well lots of things, which I won't go
      into now, but you know when you have it!
      It seems to me that, if you are are using a small diameter cutter with
      appropriate RPM and feeds, which should result in minimal vibration, you'll
      be just fine. On the other hand, if you are using a 7/8" diameter end mill
      doing some aggressive roughing I wouldn't be surprised if the end mill
      pulled down in the collet.
      It is my opinion, that in the home shop it is likely that most of our
      machining will be done in the former as opposed to the later conditions. It
      is also my opinion that if you have a lot of vibration, something is wrong
      ... either too aggressive machining or inadequate rigidity.
      The answer is easy at either extreme, but as with most things in that
      grey area, it's hard to know where the "tipping point" is. That's where a
      little experience and a lot of common sense, not to mention caution, helps!
      I hope this helps some of the "newbies" ... and some of us more
      experienced amateurs who are still learning.

      Happy chip making,

      Mario


      ----- Original Message -----
      From: "Daniel Miller" <miller@...>
      To: <mill_drill@yahoogroups.com>
      Sent: Wednesday, October 05, 2005 11:38 AM
      Subject: Re: [mill_drill] Re: New #33686


      > I'm sort of a newbie but collets seem rather straightforward--for the
      > situation William described below would an end mill holder have held
      > better than a collet, or under the same forces and vibrations would the
      > end mill holder probably loose its grip as well?
      >
      > Seems like when I use a collet I just slide in the end mill, draw it up
      > tight in the spindle, and the end mill is now basically an extension of
      > the machine. Can't see how anything else would hold better, but please
      > tell me what I'm missing.
      >
      > Thanks,
      > Daniel Miller
      >
      > Rupert Evans wrote:
      >
      > > --- In mill_drill@yahoogroups.com, William Abernathy <william@i...>
      wrote:
      > > > For most jobs they are plenty secure. For a few, they are not. I
      > > have only had
      > > > problems with collets losing their grip when cutting deep slots and
      > > had a
      > > > harmonic vibration set in. Other than that, holding tools with
      > > collets has
      > > > worked out fine.
      > > >
      > > > If collets do not hold end mills securely, why are there collets?
      > > >
      > > > --W
      > >
      > > Collets require more care and knowledge than end mill holders.
      > > Therefore end mill holders are better for newbies than collets.
      > > I stand by my advice.
      > > Rupert
      > >
      > > >
      > > > Rupert Evans wrote:
      > > > > It is not good advice to suggest that a newbie should buy R-8
      collets
      > > > > for holding end mills. He should get a 3/8" and a 1/2" end mill
      > > > > holder. Collets do not hold end mills securely.
      > > > > Rupert
      > > > >
      > >
      > >
      > >
      > >
      > >
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    • wombat4622603
      Thanks for the information; there is no substitute for direct experience. They do show six slits in their photographs, but that obviously doesn t mean
      Message 32 of 32 , Oct 17, 2005
        Thanks for the information; there is no substitute for direct
        experience. They do show six slits in their photographs, but that
        obviously doesn't mean anything.

        David Wimberley

        --- In mill_drill@yahoogroups.com, "Greg Jackson" <greg@t...> wrote:
        >
        > I buy ER collets by the hundreds. I normally use known suppliers
        that I
        > trust, but once I got stuck on a short lead time and tried to fill
        in with
        > Shars. I have never seen such junk. I sent them all back. As far
        as I'm
        > concerned, Shars is on par with Harbor Freight for quality.
        >
        > They might have been 0.0004", I don't know. That's actually a
        pretty
        > minimal spec. I do know they cut the nut grove the wrong place so
        most nuts
        > wouldn't work. They also did 4 slits instead of 6 and the slits
        didn't go
        > very far so the "spring collet" was a spring that could support a
        Mac truck.
        > It took so much force to close the collet that there was little
        clamping
        > force on the tool itself.
        >
        > G. Jackson
        > Tormach
        >
        > -----Original Message-----
        > From: mill_drill@yahoogroups.com [mailto:mill_drill@yahoogroups.com]
        On
        > Behalf Of wombat4622603
        > Sent: Friday, October 14, 2005 6:40 PM
        > To: mill_drill@yahoogroups.com
        > Subject: Re: [mill_drill]Collets vs end mill holders
        >
        >
        > Shars tool company has ER Collets with guaranteed concentricity
        > of0.0004". For example, they have a set of 11 ER-32 collets with an
        R-8
        > holder for $173.95.
        >
        > David Wimberley
        >
        >
        >
        >
        >
        >
        >
        > Yahoo! Groups Links
        >
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