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  • Who don't make mistakes ?

    OK we all make them, anyone who says they don't is only lying to themselves.

    So converting some Rotabs to stepper drive and they need a combined nut, thrust and Oldham coupling to save space, Simple bit really. Milled the Oldham coupling bit on the end and start to centre drill then drill and tap for the nut part.



    Crunch, centre drill pops it's clogs off, take it out the chuck, bang it on the vise, will the damn bit fall out [ no they never do ] so right seeing as it was the damn centre drills fault it can be responsible for getting itself out.

    Stuff it in a temporary holder so as not to burn my tiny, dainty pinkies and grind it up free hand as such.



    Front.

    and



    Underneath.
    Basically it's a trepanning tool of fixed radius when held in the tailstock chuck. The radius has to be larger than the broken bit and seeing as part of it is on the tool that's the bit you have to grind past.

    Back in the 3 jaw chuck with the part, modified centre drill in the tailstock chuck and feed in slow with lube and you will get the broken bit standing up on an island.

    I was going to take a picture of it but as I took it out the chuck the broken bit fell out and disappeared into the black hole, known all over the internet as Johns Floor ™



    Not a new idea, God knows how many decades old ? but still a time saver and I though on topic for a home shop forum.
    .

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.




  • #2
    Proof that other people do 'asplode drill bits! HA HA! I AM VINDICATED! MAHAHAHAHAHAHA!


    *bookmarks thread*


    Humor aside, nice way to save a busted bit.

    Now my question is what exactly is a "trepanning tool" and why would I need one?

    ...all I come up with is trepanation which is the art of drilling holes in the skull. My lathe at home isn't quite big enough to swing a normal sized adult and I'm not sure how to get around the neck-snapping issue. Mount 'em in the tail-stock? Or is there a fixture I need to make?
    This product has been determined by the state of California to cause permanent irreversible death. This statement may or may not be recognized as valid by all states.
    Heirs of an old war/that's what we've become Inheriting troubles I'm mentally numb
    Plastic Operators Dot Com

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    • #3
      new to me

      Hey John, good trick. I know you won't believe this but I never break centerdrills, but if I ever do I will remember this. Yes, I do use them every day but always have enough speed and coolant and make sure tailstock is dead nuts centered and be very gentle. Peter. ( Is Man U going to end up on top? )
      The difficult done right away. the impossible takes a little time.

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      • #4
        Thanks for an excellent idea and pictures to match.

        Does your QC department allow chatter marks on the bottom of a hole like that? If mine did, I'd get myself a beer and in a little while QC would quit whining.
        .
        "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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        • #5
          Waste not, want not

          Now, that gem is going to save a bit of stock and a few scribers from destruction
          Ken.

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          • #6
            Originally posted by Liger Zero
            Now my question is what exactly is a "trepanning tool" and why would I need one?

            ...all I come up with is trepanation which is the art of drilling holes in the skull. My lathe at home isn't quite big enough to swing a normal sized adult and I'm not sure how to get around the neck-snapping issue. Mount 'em in the tail-stock? Or is there a fixture I need to make?
            A trepan is a tool for cutting large discs from sheet metal. Very handy tool and surprisingly accurate I've found. Easy to make.

            Here's one: http://www.enuii.org/risley/training...ing_tool_s.jpg
            Peter - novice home machinist, modern motorcycle enthusiast.

            Denford Viceroy 280 Synchro (11 x 24)
            Herbert 0V adapted to R8 by 'Sir John'.
            Monarch 10EE 1942

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            • #7
              John, just noticed that you're out of the virgin business? Were you disqualified when you hit 61?
              "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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              • #8
                No I posted before, it was the lack of them that forced me out of business.
                The last known sighting was in 1924 on the Cadbury's chocolate firms outing going to Blackpool

                Tiffiepedia fails to publish the results of the return trip.

                .
                .

                Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                • #9
                  Thats a great idea. But why not use a carbide center drill or some type of carbide cutter to remove it? If a carbide center drill was used then the hole would not be oversized.

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                  • #10
                    Who don't make mistakes ?
                    who DOESN'T make mistakes, or was that they humour bit

                    the mistake isn't busting the centre drill, its using a centre drill when you're not drilling a centre.....I have never busted the pip off a centre drill while using a spot drill

                    using a centre drill to start a hole instead of a spot drill maybe the most common shop error; there are good practical reasons for not doing so.....yet everywhere you turn people start holes that way

                    good creative corrective action though!
                    .

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                    • #11
                      I don't make mistakse. What's the prbmleo?

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                      • #12
                        I don't make mistakes either. I'm perfect.














                        Thanks for sharing John. I hate broken center drills.

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                        • #13
                          I thought I made once, but I was mistaken...................

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                          • #14
                            Here's some other "ready made" trepanning bits for those of you that have led a sheltered life ;-)

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                            • #15
                              I have to agree with Mcgyver, I only use center drills when spotting for a lathe center. I use spot drills for locating holes, center drills are too fragile. And with a 90 degree spot drill I can do a 45 degree chamfer at the at the top of the hole in the same drilling operation.
                              Mark Hockett

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