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When drilling on the mill

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  • When drilling on the mill

    do you typically use a collet (R8) to hold the drill bit, or do you chuck the bit up in a drill chuck ? The reason I ask is it seems a collet would be more concentric and afford a couple more inches Z room. But, drill bits usually have embossed writing on the shaft which might bugger up a good collet.



    Appearance is Everything...

  • #2
    Not to mention you'd need quite an assortment of R8 collets for all the drill bits you might use!

    I use a drill chuck, personally. They make arbors that have an R8 on one side and JT on the other so you don't need a collet at all. I suppose an ER collet might work ok. Not sure how much holding power they'd have though, especially as the drill bit gets small relative to the range that the ER collet grips.


    • #3
      I use collets in the cnc mill (a mix of ER-16 and TG-75) because they are more concentric and I lose less Z clearance. But I generally use a drill chuck in the knee mill for convenience and so I don't have to stretch to loosen the draw bar (really need to build a power draw bar). From my experience, collets generally hold better, but you have to have a lot of them to cover all of the drill sizes.


      • #4
        I use both,but I also use screw machine length drills which most times eliminates the need for spotting.

        The stamped numbers I file off,not only do they prevent full contact in a collet,they also produce runout.A few strokes with a small file slicks them off flush.
        I just need one more tool,just one!


        • #5

          A centering drill in a chuck will pretty well centre itself - even in an eccentric chuck.

          I have a (metric) ER-32 and ER-16 collets, each of which has a "gripping range" of 1mm (0.040"). They grip very well indeed.

          I prefer to mark out and centre-punch all the holes I drill. The smaller/"spotting" drill works fine to pick up and locate (to) the centre-punched mark. That works just about as well on a pedestal drill as it does on a mill.

          Unless there are compelling reasons otherwise, I do all my drilling on the pedestal drill. Its a lot easier than setting up the mill.

          But, if the mill is needed - I use it.

          A vertical mill or a mill-drill used as a drill are only a better class of pedestal drill after all.

          Accurate marking out and centre-drilling are skills well worth learning - and maintaining.


          • #6
            Collets... if the drill is a nominal size.
            Drill chuck... if it's a screwball size, or if I'm Drilling and Tapping.
            (Collets hold better).


            • #7
              slight eccentricity in the drill chuck won't matter, its how how accurately the lips are ground and what its following (pilot, spot drill, centre punch mark etc) that'll determine dimension and whether the hole is straight. I use a drill chuck, way quicker than changes collets, my fav for small stuff has a 1/2 arbor which is the most frequently used collet in my mill....but like Tif said, after spotting all often just use the drill press


              • #8
                Collets, if the drill is 1/2" or bigger. TG100 on the horizontal & R8 on the knee mill.
                Chuck, if it's smaller than 1/2".


                • #9
                  For some of us there is a third alternative -Morse Taper drills... faster than any of the other solutions and they preserve the Z, and remove another source of runout.
                  I always use them when I need an accurate hole (providing I have the size of course.)

                  MT drills are useful when your Tailstock, Pillar drill and Mill all take them.


                  • #10
                    I use whatever I have at the time, ER, Chuck, and DA collets. Thats about all DA collets are good for, drilling and reaming.


                    • #11
                      OK, Looks like there are no hard and fast rules and it depends on the circumstances... Thanks all !


                      (I ended up using a Jacobs chuck )

                      Appearance is Everything...


                      • #12
                        Drill chuck for me, but you guys have given me an idea- I have a number of boeing surplus drill bits, ones which have a certain sized end to fit a purpose built holder. I could make a holder to fit those, and then make up a few more using the smaller sizes of drill bit, ones that I don't have with that shank on them. I'd just be using a bit to drill its own hole in a piece of rod of the same size as those boeing drill bits shanks. I'd have the option to crimp this onto any drill bit, providing I roughed it up enough so the crimp would grip the bit strongly enough. Conversely, I could silver solder the bit into its shank, and in either case I have the option to set the length of the bit sticking out.

                        Often enough I can't get enough length out of a small diameter bit to allow the drilling job without the chuck jaws interfering on some part. These add-on shanks would solve a couple problems, provided I could get an accuratly centered hole in the shank piece.
                        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


                        • #13
                          I used to use a chuck a lot until I got an R8-ER40 collet chuck. Now I just grab a collet and drill, and rarely ever use a drill chuck.

                          One downside to the ER chucks is that all my drill chucks, boring heads, facemill arbors, etc are R8 native, so to use those I have to remove the ER-40 chuck.
                          "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."