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Left hand drill bit??

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  • Left hand drill bit??

    OK...........I've got to there some "special" reason for having a left handed drill bit.

    I saw some advertised and cannot figure out what they would be good for except for a broken drill that will "only" work in reverse........

    A "hole" is a "hole".......whether drill clockwise or counter clockwise.........Right??

    Can someone explain what they are for??


  • #2
    one use for left hand bits is when you are drilling out a broken off bolt. A right hand bit will try to screw it in further, while a left hand one tends to unscrew it. If you are lucky (seldom happens) the broken bolt might come out when you drill with the LH bit.
    I think there is another use, but can't think of it right now. John


    • #3
      They are used for removing broken bolts. By drilling in reverse when the drill bites at the end of the hole if will spin the bolt out instead of in.
      Mark Hockett


      • #4
        Left-handed drill bits

        They are of course rotated "back-wards" - true - no joke!!

        They are primarily for drilling out jammed or rusted bolts,studs etc. They will sometime cause the thread to "walk out". The principle is the same as "screw extractors" - aka "Ezy-outs".

        It surprising how much concentration - for me anyway- when you've had a long time developing the skills and habits of sharpening right-handed drill bits!!


        • #5
          I understand left hand drill bits are used in some multi-spindle drilling machines where the adjacent chuck have opposite rotation.

          Frank Ford


          • #6
            Right hand drill bits for right handed people and left hand drill bits for left handed people, just like batters and golfers!!
            The shortest distance between two points is a circle of infinite diameter.

            Bluewater Model Engineering Society at

            Southwestern Ontario. Canada


            • #7
              Left-hand drills are used in gang-drilling machines-particularly those used to drill those rows of holes in the side panels for adjustable shelving. Every other drill is left-handed and this elliminates the need for an idler gear between drills, and allows closer spacing with a simpler gear box. Duffy
              Duffy, Gatineau, Quebec


              • #8
                They are often used in the back side spindles of screw machines, for drilling the back of parts after they are cut off. I used to have a set of fraction and number lefties. Later, when I got to dealing with graduate students and PhD's they came in handy, just the thing to drive the "smart people" nuts. The time spent regrinding them was worth it.



                • #9
                  What about left-handed allen wrenches?


                  • #10
                    left handed drills

                    They are to drill holes for tapping left handed threads


                    • #11
                      Originally posted by Frank Ford
                      I understand left hand drill bits are used in some multi-spindle drilling machines where the adjacent chuck have opposite rotation.
                      Indeed, I have seen such creatures.
                      Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
                      ~Practitioner of the Electromechanical Arts~


                      • #12
                        And here all this time I thought the left handed drill bits were for use south of the equator to counter act the Coriolis effect, you know, the way water swirls down the drain in a different direction down there, and that if you didn't use a left handed bit south of the equator, it would spin you into the ground.

                        And if you buy that, I have a big gold bridge I'd like to sell you too!
                        NRA Life Member


                        • #13
                          Left handed endmills are available for the same reason as Frank
                          Ford mentioned. Not for nothing are most single spindle mills
                          (as opposed to ganged mills) made with forward and reverse.


                          • #14
                            Down under

                            Dead right Steve.

                            Its "different down-under".

                            If you are gunna get screwed here it will be with a left-hand thread.

                            We have a good line in gold-bricks too.


                            • #15
                              Multi-spindle drill heads

                              I just need one more tool,just one!