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  • Reamers

    I am changing the design on the tool I am (re)designing. I'm thinking of using a precision(?) reamer to get a hole to size. Having never used a power reamer before, I need some advice and direction before proceeding. All work is done on my little 4 x 10 lathe.

    I'm drilling a center hole in 7/8 - 14 threaded rod, 1.5" deep, 0.440" diameter. I will have a hole 3/8" already in place. Can I proceed from there, or shall I first enlarge my preliminary hole with a 7/16" bit before attacking it with the reamer? The reamer:

    http://www.ebay.com/itm/250463876973...84.m1423.l2649

    Pops

  • #2
    7/16" = 0.4375" You want 0.440" That's only 0.0025" difference. The 7/16 bit will likely be oversize by more than that. Perhaps 27/64 (0.421875") would be a better choice.

    The rule of thumb I've been told is to drill 1/64" smaller and then ream.

    Andrew

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    • #3
      I second Andrew. Use coolant and ream at half drilling speed. Around 300 to 350 Peter
      The difficult done right away. the impossible takes a little time.

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      • #4
        Personally, I would bore it out to around 0.420" and then ream it
        Tel

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        • #5
          Here's some reamer info. Maybe a lot to digest.http://www.yankeereamer.com/techinfo.asp

          Hope this helps. Allen

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          • #6
            Do a test hole in a scrap piece to see if the 7/16" bit you have will drill oversize. If you are really concerned bore it as suggested before.

            There is no magic to a reamer that I know of, just go a bit slow and put it in a nice tailstock chuck.

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            • #7
              Crisco shortening for baking works real well when reaming too. Idea is stolen from one of the Machinist's Bedside Readers. Load the flutes and it both lubricates and drags the cuttings out too. Clean the tooling, Hole real well afterwards. Rancid animal fat in any cut would not be pleasant.

              I'd also agree about boreing first before reaming for anything critical. Then again that's a long small diameter hole.

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              • #8
                Your final hole size will also be affected by the concentricity of the 3/8" hole and the runout of your work holding device. The more runout the larger the hole. So I would recommend drilling and reaming in one set up, if possible. If the 3/8" hole is already in the part there's not a whole lot you can do about that.

                You may also want to check into decimal sized reamers that are available from multiple distributors. If push comes to shove you may even want to go with an adjustable reamer. No you're not suppose to use them as machine reamers, but I have done so as have many others.

                BTW, the recommendations for vegetable shorting and drilling 1/64" under are right on the mark.

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                • #9
                  Originally posted by Tel
                  Personally, I would bore it out to around 0.420" and then ream it

                  Yup ! Sounds like a winner.

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                  • #10
                    One thing I didn't mention is that only the first 1/8" of the hole is critical in size, with the rest being just clearance critical.

                    This is the type of information I'm looking for (and, have come to expect, here) so keep 'em coming, please.

                    Pops

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                    • #11
                      Will the hole be precisely centered- or does it matter? It's not easy to accurately chuck threaded rod, nor measure it for concentricity. Is this a part of the equation in this project?
                      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                      • #12
                        Originally posted by darryl
                        Will the hole be precisely centered- or does it matter? It's not easy to accurately chuck threaded rod, nor measure it for concentricity. Is this a part of the equation in this project?
                        I'll be coming in from the front of the unit with a 3/8" cut to depth, then following with the sizing. I'll be drilling through the guide plug in the outer nut, then through the cutting plate, then into the threaded rod. Without changing the set up, I would then like to size/ream the cutter plate and the rod hole. Then, without changing the set up, I'll cut the guide angle for the plunger. That should give me the concentricity I need, as all three holes are drilled on the same line.

                        Therefore, I will set the threaded rod in the chuck, align it to rotate true with the DI. Then I'll mount the end nuts, with the delrin plug in place. At that point, I am into the precision cut portion of the job.

                        Pops

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                        • #13
                          "Guide plug"? "Cutting plate"? What in the world are you talking about?
                          How long is this piece? If you want it concentric, put it in a collet and BINGO, there it is. If it only needs 1/8" on size, how will you get the clearance behind that area?

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                          • #14
                            Originally posted by tdmidget
                            "Guide plug"? "Cutting plate"? What in the world are you talking about?
                            How long is this piece? If you want it concentric, put it in a collet and BINGO, there it is. If it only needs 1/8" on size, how will you get the clearance behind that area?
                            Die, cutter, shaping rod, push mandrel, all-in-one.

                            The 1/8" critical at 0.440" is part of the shaping portion of the operation. The hole in the threaded rod is to be about 1.5" deep, but only a tiny bit at the beginning is critical in diameter. Once the cutter ram is past that, all I need is clearance behind that point to allow it to bottom in the shaping cylinder.

                            Imagine this a bit. Hold a piece of threaded rod, 7/8 - 14, 2.5" long, faced on each end in your hand. Looking at one end, you will see a 3/8" rod screwed into it. At the other end, you will see a pair of 7/8-14 nuts, silver soldered together, looking like one nut. There will be a slit of ~0.030" at the join. The outer nut will be filled with a Delrin plug. Now, looking at that plug, you will see a countersunk hole, ending in a round hole, 0.440" in diameter. If you look down into that hole, you will see the other end of the 3/8" rod, which is 0.157" diameter (+- 0.001") with a domed tip at that point. Now, pick up a piece of 1/2" CRS rod, 2" long, with a 60* countersunk in the end, ending in a 0.21" (+-0.001") hole. The first 1.25" of that 1/2" rod has been reduced to 0.437" (+- 0.001".)The other end of that rod has a 1/4" hole in it that ends in a shoulder down inside.

                            You now have seen the device I'm re-designing. Some day I'll have pictures to share.

                            Pops

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                            • #15
                              No, I haven't seen diddly squat. Post a picture or forget it.

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