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While I am on milling machines...

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  • While I am on milling machines...

    The milling machine that I purchased ( has an MT3 for mounting cutters.

    Current choices are a collet (for eg., that would be held with a drawbar. It's opening would correspond to the diameter of the end mill.

    Alternately, I could use an end mill holder (for eg., also retained with a drawbar. In this case, there is also a screw that engages a flat on the milling cutter's shank (Weldon style).

    Which style would offer more accurate tool location - ie, less runout? Or, would it be too little to matter?

    The above aside, the end mill holder offers the additional security of the screw that physically locks the end mill into the holder (of course, the drawbar locks either one into the milling machine spindle). Since the collet lacks a physical lock - friction retention only - onto the end mill's shank is there a risk (slight, moderate or extreme) of the end mill being pulled from the collet due to forces exerted during milling? If yes, what precautions are required?

    Is there a better way to install end mills?

    This begs the question, I suppose of what should I do with larger cutters:
    for eg., a fly cutter, a face mill (machine specs say up to 2-1/2 inches is acceptable) or a micrometer boring head. I expect that each one would have an MT3 shank threaded for a drawbar but if not...?

  • #2
    FWIW, I use a shop built fly cutter in the collet on my machine. I use collets rather than EM holders as that's what 'skinner had when I bought the machine.

    My insert mill has a MT3 taper...
    Design to 0.0001", measure to 1/32", cut with an axe, grind to fit


    • #3
      Dunc...I use all EM holders on my mills. I have some BB ones also. They are very good as far as runnout goes. I just like the locking screw idea...personal preference.
      I have tools I don't even know I own...


      • #4
        The mt3 collets will hold plenty strong for your mill and would be the cheapest route. I have several mt3 collets and they work but I'm not a big fan of them. Endmill holders are a step up over a mt3 collet IMO.
        Down the road a mt3 tapered er32 collet chuck/set would be nice to have and will serve to hold all your end mills and drills with it's wide closing range.
        A good er32 set is expensive though. I have a ETM er32 and er11 set which are quite nice with very low runout.

        Boring bars and fly cutters, etc can be had with mt3 tapers or a 3/4" straight shank and I don't think on the smaller mills it makes much of a difference.



        • #5

          I'm not dead certain that I am correct, but I just don't like any unnecessary multiple insert/removals of tapers in my machine spindles. It has the potential to not only wear the spindle taper but to damage it with inclusions of grit etc. between the spindle taper and that of what-ever is inserted into it. It will happen. Its just a matter or managing the risk. "Wear and tear" is inevitable and increases with use. The best way is to reduce the risk of multiple changes. "Hurry" and "haste" don't help much either.

          They are the reasons that I use collet adaptors and drill chucks.

          I accept that "adaptors" do introduce an additional source of risk of "alignment/run-out" error - but I can quite easily manage or cater for that - "re-doing" the taper in a machine spindle is another matter. In my shop collets, drill chucks and collet adaptors are in the "disposable/consumables" category here as they are relatively easily replaced.


          • #6
            With the collets you will be holding closer to the bearings. Not a bad thing in a mill, especially a small one. Now i have never used the Morse taper collets so I don't know if they suffer from the same problem as R-8s in which the cutter can suck out. If they do I would consider the end mill holder style. Especially if most of you cutters are going to be the sam shank size.
            Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.