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how to use an expansion reamer?

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  • how to use an expansion reamer?

    I have a project coming up where I will need to ream a 0.751 bore - I am making an undersized clutch slave cylinder to reduce the pedal travel (increased actuation effort is not a consideration). Rather than buying a new chucking reamer, I searched thru my bin of odd lot reamers (auction clutter, items bundled with what I was buying at the time) and found two 3/4 inch expansion reamers. I have used adjustable reamers in the past but never an expansion reamer. My understanding is that the adjustment feature is intended to accommodate reamer wear. For a one time use in brass, I would like to adjust the reamer .001 oversize. What do I need to know beforehand to adjust, to use, to avoid doing? TIA
    Click image for larger version

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    Metro Detroit

  • #2
    If these are like mine they are HAND reamers not machine. I used them by hand in steel, slow, plenty of cutting oil, very fine adjustments checking size after every small cut until correct size is reached. They bind quickly if you don't take very small incremental cuts and depending on the length of cut are easily cocked. I used a tap tee handle and learned to go slow and easy. Brass is grabby so take that in mind. More about what you are reaming and size would be helpful.

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    • #3
      Use a .750 solid reamer and hone to fit.
      Why note bore it to .751" ? ? ?


      -D
      DZER

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      • #4
        I agree with Vectorwarbirds in that it is a adjustable hand reamer, not an adjustable machine reamer. If you choose to drive it by machine, remember to go slow, slow with plenty of oil type cutting fluid. I would be careful to try it out on a piece of like material scrap.

        Sarge41

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        • #5
          They are also only useful for through-holes, as they cannot "bottom".
          4357 2773 5150 9120 9135 8645 1007 1190 2133 9120 5942

          Keep eye on ball.
          Hashim Khan

          Everything not impossible is compulsory

          "There's no pleasing these serpents"......Lewis Carroll

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          • #6
            Adjustable reamers are finicky to get set to the right size. Since they aren't solid, they have a bit of flex and sometimes tend to bind in the hole. If that happens, try to push or pull it straight out rather than turning backwards. Best to start undersize and work your way up. Measure the hole it's making, not just the reamer.
            Kansas City area

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            • #7
              Doozer: "Use a .750 solid reamer and hone to fit.
              Why note bore it to .751" ? ? ?"

              I need a better surface finish than I can achieve boring. I am trying to use what I own (the two reamers in the original posting) - if not, I would have to buy a chucking reamer and if I am buying new, I might as well buy a 0.751 reamer - I am just trying to avoid spending $25 for a one time use.


              vectorwarbirds & sarge41
              This is what I understand to be an adjustable reamer:

              Click image for larger version

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              The one in the image above has a range of 19/32 to 21/32 with 6 cutting edges - they are a miserable excuse for a reamer but with an infinite adjustment range and a very finite hobbyist budget range they are what I typically use and I agree they are prone to chatter. The expansion reamers shown in my original image do not have a range listed and have 8 cutting edges. I plan on doing a test ream but figured I might shorten my learning curve by asking if anyone had experience with the style of reamer in my original post. I found this description of an expansion reamer (just not hints on how to use it correctly) while searching for usage tips. https://external-content.duckduckgo....6pid%3DApi&f=1

              Metro Detroit

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              • #8
                Why not lap it out?

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                • #9
                  ----D
                  DZER

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                  • #10
                    At risk of taking this too far off the OP's question, the brake cylinders I have been around won't care about .001" or even more off of nominal. That is, If he's using the typical aluminum piston and rubber cup seal.
                    I cut it off twice; it's still too short
                    Oregon, USA

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                    • #11
                      Yea I forgot and someone else mentioned DO NOT TURN IT BACKWARDS! The blades are easy to break, if it sticks or binds loosen/retract the blades, remove and start again. If you use it on a machine it will break! Trust me...

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                      • #12
                        It's difficult enough to use a straight flute reamer in brass, never mind an expanding type. I would explore other options first.

                        You say in post #7 that you need a better finish than from boring. What do you have for a boring setup? When done with the right tool geometry a bored finish in brass can be very smooth, and accurate.

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                        • #13
                          Forget about expanding reamers. Just use a standard 3/4" machine reamer to get to 0.750, then spill ream it. Thats simply packing wooden spills down several of the flutes on one side, and taking the reamer through again. Thats always good for taking out an extra thou or so.
                          'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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                          • #14
                            If you are having a hard time getting a good finish with boring
                            you will likely have a challenge getting a good finish with a reamer
                            not to mention keeping the hole straight and round, something that
                            is almost easy to achieve with boring.

                            -D
                            DZER

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                            • #15
                              Originally posted by Richard P Wilson View Post
                              Forget about expanding reamers. Just use a standard 3/4" machine reamer to get to 0.750, then spill ream it. Thats simply packing wooden spills down several of the flutes on one side, and taking the reamer through again. Thats always good for taking out an extra thou or so.
                              This^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^
                              4357 2773 5150 9120 9135 8645 1007 1190 2133 9120 5942

                              Keep eye on ball.
                              Hashim Khan

                              Everything not impossible is compulsory

                              "There's no pleasing these serpents"......Lewis Carroll

                              Comment

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