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Re: Milling large volumes

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  • Clive Foster
    ... Gents I can confirm that attempting to use an end-mill in a normal drill press will cause the chuck to walk out if it is on a separate morse taper arbor.
    Message 1 of 2 , Dec 2, 2003
      >
      > --- In taigtools@yahoogroups.com, "Del Stanton" <delstanton@h...>
      > wrote:
      >> Drill press chuck are usually installed with tapered arbors that are
      >> pressed into the spindle. Unlike the arbor on a typical milling
      > machine or
      >> CNC mill this arbor is just a "jam fit" ans side loads might cause
      > the chuck
      >> to fall out. Let me sat clearly this inofrmation comes from
      > reading, not
      >> from direct experience. But i have always heard the drill press
      > arbors or
      >> not set up to take side loads.
      >
      > This indeed is true. It is, as you call it, a "jam fit". I had the
      > priviledge of putting my drill press together from parts, and I
      > remember that.
      >
      > I toyed with the idea of modifying the arbor so it could accept
      > anything that has a 3/4-16 thread, essentially making it into a cheap
      > mill, but the accuracy of Z-axis would be horrible - plus/minus
      > something like .2" and it is not rigid with respect to side-to-side
      > forces either. At least, that's what I found to be true with my
      > craftsman drillpress. Plus I am not sure what bearings they use, so I
      > would probably kill the poor thing altogether with excessive forces in
      > the directions a drillpress is not supposed to take. There is just no
      > way to get around getting a mill someday, is there? :)
      >
      > I did get some nice ideas here though - thanks to all who responded.
      >
      > Vlad

      Gents
      I can confirm that attempting to use an end-mill in a normal drill
      press will cause the chuck to walk out if it is on a separate morse
      taper arbor.
      The chuck wont walk off a good jacobs taper so if its a press fit on
      the end of the spindle you will almost certainly be OK providing the
      tapers are somewhere near accurate.
      Unfortunately the end mill will probably walk out of the chuck! The
      spiral side flutes put a decent pulling force on the mill which the
      hard steel on hard steel grip of the chuck jaws just wont withstand for
      long.

      Light end milling on drill presses is possible. Some makes were
      specifically made with that capability eg Fobco but the bearings etc
      are a cut above the usual.
      However you can upgrade, within reason, even a cheapy for light milling.
      Do it somewhat like this:-
      To start with it is best to pick one with a morse taper arbor and a
      proper spline drive from the pulley. A single slot key-way drive can be
      used but you ill almost certainly have to make a snug fitting, full
      depth key properly retained in the drive pulley. Hard work if you
      don't have machine shop access 'cos its gotta be accurate.
      Make the end-mill holders from blank end morse taper arbours, one for
      each size of milling cutter shank. Plain holes with a side set-screw
      engaging in a flat on the cutter shank will do fine (its what is used
      for the throw-away cutters after all) but if you are feeling swanky
      thread them as well for screw in cutters. You can buy suitable morse
      taper holders but they are threaded for a draw-bar so you need add a
      tang substitute so that the ejector drift has something to work on.
      A hollow cap nut passing over the business end and screwing onto the
      spindle will stop the end-mill holder walking out. Depending on sizes
      you may want to weld on a washer to the big end of the morse taper to
      give the cap nut more to register on. Obviously the hole in the cap
      nut must pass all sizes of end mill holder.
      You need a better down-feed. Basic principle is a substantial bracket
      on the bottom of the quill with some sort of screw thread arrangement
      to push things down. Time to get creative I'm afraid but its probably
      best to have a coarse adjustment slide movement which can be locked so
      the screw thread is only used for fine adjustments. Include suitable
      reference faces so you can use your digital calliper as a down feed
      measurement device.
      Fit a good solid quill lock clamp. Squeeze is probably better than
      screw in but really the drill layout determines what you can do.
      What you do to upgrade the bearings is again dependent upon how the
      drill is designed. Perfection is the ball thrust, needle roller side
      bearing units made by SKF and others but a pair of those will prolly
      cost about twice as much as the drill did! If you are lucky simple
      substitution of good quality bearings for the originals will do the
      deed. I think the best method is to use a pair of taper roller
      bearings but these will cost you a bit of quill movement as the
      relatively large diameter will require a pair of carriers to be pressed
      on to the quill to hold the outer races. Collars on the spindle will
      hold the inners in place but you need to make provision to get the end
      pre-load right. Shims are best but need a few trial assemblies and
      appropriate comments before you are finished.

      User strategy is obviously to set the cutting depth, lock everything up
      and feed across. Apart from getting hold of, or making, suitable feed
      slides the biggest problem with a converted drill is the difficulty of
      doing a accurate down-feed cut. Naturally you have the table to quill
      registration problem endemic to all round column mill-drills to cope
      with as well.

      Its a lot more work than it seems at first sight. I converted a BIG
      power feed drill to a mill for a friend somewhat in this fashion but
      that has a no 5 morse up the spindle and suitably huge bearings so it
      was all much easier.

      HTH.

      Clive
    • Larry Richter
      Well, here I go again, into shop rumor territory. There is supposed to be a fluid coating that increases the friction between chucks and gripped tools. I
      Message 2 of 2 , Dec 2, 2003
        Well, here I go again, into shop rumor territory. There is supposed to be a
        fluid coating that increases the friction between chucks and gripped tools.
        I don't know what it is or what it looks like or how it works, just that
        there is such a thing. Duh. And double duh.

        Before being proofed the above read "gripped tooks". Which would be good
        fun for Tolkien fans. Maybe.

        Happy Holidays
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