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How would you finish bore this I.D.?

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  • How would you finish bore this I.D.?

    I'm wondering if anyone has any ideas that I haven't thought of on this. I use a Nardini MS1440 lathe. I need a way to quickly bore a finished I.D. of 2" in 2.25" x .250" wall DOM. The depth will be approximately .750".

    I currently perform a similar operation on a different part (1.3125" bore) by rough boring it to 1.300" using a boring bar, then run a shell reamer through using my tailstock. I would do this operation the same way but a 2" shell reamer arbor uses a 4MT and my tailstock is a 3MT. I know I could use a reducer adapter but that gets kind of clunky.

    Would it be possible to do this operation using a shell end mill on a 3MT arbor in the tailstock? If I can't do the bore quickly and accurately then the part will not be cost effective for me to produce.

    Bob

  • #2
    Are you really getting as good or better finish using the shell reamer?

    What about making a holder for the 2" shell reamer or an adapter that you can use on your current #3 MT holder?
    It's only ink and paper

    Comment


    • #3
      Dihart cutters are also a great way to get an accurate finished bore..
      ALthough they say they are for ally...the ones I have cut brass and mild steel with no problems..

      Rob

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      • #4
        [QUOTE=Carld]Are you really getting as good or better finish using the shell reamer?[QUOTE]

        I do not get as good of finish with the reamer as the boring bar produces. What I do get is accuracy with very little time investment. These are small production runs of 10-20 parts. Each end gets bored so that's 20-40 finished I.D.s. My current workflow on the smaller part is to face the part, run a single .060" cut with a boring bar, ream to final I.D., chamfer I.D., debur O.D., flip, measure part length, and repeat. I can knock out about four an hour doing it this way. I already know that I'll have to take two cuts with the boring bar on the larger part so time starts to add up. I can hold good tolerances with a boring bar but, that takes time.

        Bob

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        • #5
          Bob,

          Can you hold a 2" shell reamer in your toolpost? If you can buy or make a floating holder, it'll make alignment less of an issue.

          Ian
          All of the gear, no idea...

          Comment


          • #6
            Bob, I figured that was why you used the shell reamer but just checking.

            The second part of my question was, can you make an adapter to fit the current holder and put the 2" shell reamer on? If there is some way to make a sleeve spacer and still have the dogs lock into the shell reamer it may work or you could machine dogs 90 deg from the other dogs and still use the 2" shell reamer.

            What about turning down a #4 to a #3 taper?
            It's only ink and paper

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            • #7
              I would go for turning the #4 down to a #3 as mentioned above. Yes you can use a shell mill, but milling cutters always make an oversized hole compared to the actual tool diameter. The amount of oversize is not usually something to be relied on.

              Comment


              • #8
                Ideal sounding part for a turret lathe, but I would make up my own MT3 arbor for the shell reamer or turn down down the MT4 to MT3 if it wasnt too hard.

                Comment


                • #9
                  Bob,
                  What is the tolerance your trying to hold ?

                  If the boring tool is making a good finish, could you
                  just come up with a way to set that final cut accurately ?

                  You have tried a minmag (base) and a 1" dial indicator
                  on the cross slide ?

                  Totally dispense with the tailstock operation, would shorten the
                  time somewhat, I would think.

                  Comment


                  • #10
                    I might think about using a boring head in the tailstock and set to the finish size.
                    Paul Compton
                    www.morini-mania.co.uk
                    http://www.youtube.com/user/EVguru

                    Comment


                    • #11
                      +1 on the boring head in the tailstock. I would do that for sure because I have an MT3 boring head.

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                      • #12
                        How are you going to feed a boring head mounted in the tailstock ?

                        Hand feed (I have to assume) for this finish cut, I believe would
                        be ugly.

                        Comment


                        • #13
                          My metalwork teacher would have poured scorn on anyone who couldn't achive a consistent finish with hand feed. We were expected to face 4" diameter and turn 6" shafts. I can still do it 25 years later and indeed have to on the knackered ML7 at work. I don't LIKE having to do it and would always opt for a lathe with self-acts, but it's really not that hard, just dull and tedious.
                          Paul Compton
                          www.morini-mania.co.uk
                          http://www.youtube.com/user/EVguru

                          Comment


                          • #14
                            I'm thinking that turning down the 4MT arbor on the shell reamer is probably the best way to go. This bore is for a 2" tapered roller bearing race. Accuracy needs to be +0, -.001. I know that a 2" shell reamer doesn't exactly get me that accuracy but I've found that if I burnish the edges of the cutter down with a piece of drill rod, I can get there. I've never cut a MT before. Would it be best to take it to a grinder or is it something I should be able to do myself?

                            Bob

                            Comment


                            • #15
                              You could try to get a BIG tap wrench on the shell holder and float the reamer on a center in the tailstock.
                              You just need to stop the spindle as the reamer breaks thru.

                              It's quick, and you probably already have all the stuff.

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