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Why are machine reamers so long

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  • Why are machine reamers so long

    The title pretty well asks the question. I was drilling and reaming some 1/2 inch holes this afternoon. The secquence was locate hole, drill hole 1/64 under 1/2 inch and then crank the table down a bunch so I could get the reamer in the chuck. Ream the hole,then remove the reamer and then crank the table up to get ready to drill another hole. I know I can cut the shank of the reamer to a shorter length but is there a reason to leave them full length?

    Thanks
    Pete

  • #2
    With a lathe unless you have a perfectly aligned tailstock holder, the longer shafts tend to flex more and not push as hard off-center. A drill chuck is not a precision holder for a reamer. One day I'll buy/make a floating holder.

    For a mill it's less important, but will help if you are using a chuck.

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    • #3
      Yes, flex is the answer.
      As not to influence hole size with eccentricity.

      --Doozer
      DZER

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      • #4
        That's a continual aggravation with reamers on my mill/drill that doesn't have a knee and loses location if you raise the head. My kludge has been to make some collets for the reamer shanks (which aren't in 1/16" increments) so I can poke them up the 1/2" collet a ways and shorten them up. Overhanging length then is more nearly like the chuck and standard drill bit.
        .
        "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
          Another way to look at it is that you can always shorten the shank, but it would be be far more problematic to lengthen it.

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          • #6
            Why are reamers so long?


            Because the bean counters haven't tackled them yet. Just wait until one of them gets some spare time. You will be begging for the old fashioned, long reamers to return.
            Paul A.

            Make it fit.
            You can't win and there is a penalty for trying!

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            • #7
              Maybe they are used for smoothbore pistols and rifles?

              Checking out reamers on McMaster, I found they have MT2 tapered reamers for $70. Might be handy to make toolholders such as the one I'm considering for the boring bar head:
              http://www.mcmaster.com/#reamers/=prrf8i

              Apparently there are situations where the length of the reamer is useful, to access a hole in an assembly, perhaps. They have extra-long reamers:
              http://www.icscuttingtools.com/catalog/page_193.pdf
              http://pauleschoen.com/pix/PM08_P76_P54.png
              Paul , P S Technology, Inc. and MrTibbs
              USA Maryland 21030

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              • #8
                That's because what you have are not machine reamers. Machine reamers have morse taper shanks and parallel flutes, so only cut at the nose end. If you are using ones with parallel shanks and a square on the end, they are hand reamers, which have taper flutes for about half the flute length, and parallel for the rest.

                Richard
                '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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                • #9
                  Originally posted by Richard P Wilson View Post
                  That's because what you have are not machine reamers. Machine reamers have morse taper shanks and parallel flutes, so only cut at the nose end. If you are using ones with parallel shanks and a square on the end, they are hand reamers, which have taper flutes for about half the flute length, and parallel for the rest.

                  Richard
                  Actually that statement is not entirely true and possibly a little misleading Richard.
                  Machine reamers or chucking reamers can have straight or MT shanks and can have straight or spiral flutes, though always parallel of course and entirely correct that they only cut on the nose end.
                  If it has a square on the end then you are quite correct in that it will be a hand reamer.

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                  • #10
                    Originally posted by Peter Neill View Post
                    Actually that statement is not entirely true and possibly a little misleading Richard.
                    Machine reamers or chucking reamers can have straight or MT shanks and can have straight or spiral flutes, though always parallel of course and entirely correct that they only cut on the nose end.
                    If it has a square on the end then you are quite correct in that it will be a hand reamer.
                    Yes, of course you are right, I'd forgotten about chucking machine reamers.

                    Richard
                    '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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                    • #11
                      They are Chucking Machine Reamers with parallel flutes. So what does a "floating holder look like or even better who has a set of plans for one.

                      Thank you for all the replies, I guess I will look at the table cranking exercise as a reason I don't need a gym membership.

                      Pete

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                      • #12
                        A floating reamer holder allows the reamer to be off center, not wobble, just be out of alignment with the hole. I'd have to think about it a bit, but I believe they're used only where the reamer is not rotating, the work is. In the CNC lathe we use very short stub reamers with good results.

                        No, I don't think reamers are meant to flex to follow a hole. The usual procedure is to drill, then bore to align the hole for reaming.

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                        • #13
                          I basically agree with DR. I asked this question a long time ago. The answers were very similar to this thread re: flex. I don't really buy into that argument -- not least of which because if it does, the resulting offset still will affect hole cylindricity and size. Expecting a solid steel shank to 'S' bend is a little much. The inaccuracy, at least, has been proven out in my own workshop experience.

                          I don't really understand the very high cost of "floating" reamer holders. All I can guess is that it is a bit specialized so not sold in the large quantities of more common tooling. For any hole, say, over 1/4", a boring bar will very near always produce a more accurate bore with precision matched by the operator controlling it. Very inexpensive too, in comparison. If you would like to make a holder, though, inexpensive kits + plans are available from Hemingway Kits.

                          There are a number of variations in design for floating reamer holders. Some contrain the movement to eccentricity while maintaining angular parallelism. Others control both and allow independent adjustment of each. Still others are as simple as sandwiching the tool mount from the outer holder body with an o-ring. That is how most straight shank, turret lathe holders are historically made (Brown & Sharpe No.67). Those type are also the most numerous to find used -- and the least expensive. Other designs often use wave washers with a solid nut to compress them. This makes for more or less restriction to movement. The currently produced ETM holders rely on ball bearings which are mounted to races restricting possible movement either laterally or angularly. (Never seen inside one of those. My understanding may be incorrect there). Basically, the whole lot relies on a tool mounting interface that is loose in a housing with two pins on the back. The two pins are driven by two oversize, (usually blind) bores in the holder body.

                          It may sound like a complicated ruse, but the accuracy of the bores in relation to reamer size is dramatically increased when these holders are used. That is my experience with them. It also can help for tool length variation. There is absolutely no benefit to leaving a long shank with a reamer held in a floating holder. You can shorten them right up to the mounting nose of the holder. You may even notice in some older machining texts the mention of a reamer designation specifically shortened. Maybe 'screw-machine reamers' or 'turret reamers' or... ? I don't remember. They may still be available, but they're certainly not in any of the modern catalogs I've seen.
                          Last edited by Arthur.Marks; 12-12-2013, 12:41 PM.

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                          • #14
                            Those of us that use "mature machines" in our shops find out that drills only drill "kinda round" holes. The quality of sharpening, feed rate, and material among other things affect the size and roundness of the hole produced. A bored hole will be much closer to round than a drilled hole. I was taught drill, bore, ream in that order and with each speed and feed appropriate.

                            Yesterday, just for giggles, I skipped the bore part of the process. The result was the reamer followed the path of the drill and produced a off-sized hole. Same drill but with the boring step included produced an on-sized hole.

                            The temptation is to cut the reamer to a shorter length. This will be followed by needing to have all the length of a factory fresh reamer.

                            Thanks for all the input
                            Pete

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                            • #15
                              Originally posted by Stepside View Post
                              They are Chucking Machine Reamers with parallel flutes. So what does a "floating holder look like or even better who has a set of plans for one.

                              Thank you for all the replies, I guess I will look at the table cranking exercise as a reason I don't need a gym membership.

                              Pete

                              THIS is floating reamer holder


                              Z

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