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  • #61
    Interestingly enough, it is not strictly necessary that the taper fit well in order to lock. Note that in the inclined plane problem, the contact area doesn't appear in the formulas. A larger area does not give us more "friction force."
    Yes, it does. The reason stiction exists is the operation of the Van der Waals forces. These are area dependent in a direct ratio assuming the surfaces are in sufficiently close contact. The better the fit of the taper the higher the stiction force that must be overcome to make it move again. This is also why PTFE doesn't exhibit stiction. It has no exposed dipoles and doesn't display externally visible Van der Walls forces from the molecule. Stiction isn't friction but the distinction is irrelevant when holding power of the taper is the issue.
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    • #62
      Duplicate post somehow.
      Last edited by JCHannum; 02-10-2008, 04:09 PM.
      Jim H.

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      • #63
        Holding two Morse tapers together as Evan describes is of little use, as it merely tells whether they are the same or different. Again without a known standard, it is not much use.
        Ahem, I gave a known standard, a taper that fits correctly. That is all you need to compare to. That is also all I needed to make a #2 MT last night that fits correctly.
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        • #64
          Mercy, I have tried not to become personal, and certainly have made no reference to your financial practices or parentage.

          You have never displayed a reluctance to present your views on a subject, and are frequently critical of others. I find it surprising you take offense when someone offers opposing views of your posts.

          You have stated the taper was out of spec. I questioned how you determined this, since you had no true reference. When two or three items are compared, one can only determine they are the same or they are different unless one is a known standard. In this case, none of the tapers was.

          You have since made an attempt to measure them, in your own words; "a close rough estimate". Measuring a taper with a micrometer with flat faces is very difficult. It is not a problem on the large end if there is a sharp break, but the small end is problematical. It is also very difficult to locate the exact point where the measurement is made, and difficult to measure the linear distance between the two points. This is what I referred to. Truly accurate measurements will require some rather complex setups, probably a sine bar, Jo blocks and a height gage on a surface plate is the best setup for the home shop, and I agree with you that the exercise is not worth the effort.

          Holding two Morse tapers together as Evan describes is of little use, as it merely tells whether they are the same or different. Again without a known standard, it is not much use. As you pointed out that method has it's own inaccuracies.

          I am not picking on you (maybe I am a little), but just trying to point out that some things are not always as simple as they seem. I don't know if the Indian taper is out or not. It probably is, and the Bison probably is very close to ideal. For most applications, the Indian taper is probably acceptable, for yours, it is not.

          You do present a very good point in that it is prudent to inspect your purchases to make sure they are capable of giving you the results you are looking for.

          As far as Morse Tapers and the purpose of the tang, I have presently four sources that identify the tang is to drive or share the driving of the drill. These are three text books and one manufacturer's handbook as follows:
          "Machine Tool Operation" Henry Burghardt 1919, Part 1, page 142
          "Bendix Cutting Tool Handbook" copyright 1972, page 169
          "Machine Tool Operation" 1959 Burghardt, Axelrod and Anderson, pp 175 & 176 (While this is the same title and shares Burghardt as author, it is a complete rewrite.)
          "Metalwork Technology and Practice" 1975 Ludwig, McCarthy and Repp, page 483

          If anyone cares to refute the purpose of the tang, I request that he provide as least as many documented references stating that it's only purpose is to expel the drill.

          The Morse Taper was developed over one hundred years ago as a means to drive a drill. For whatever reasons, it has become a standard in many applications. When it was first designed, the horsepower of today's machines and the materials encountered in tools and workpieces were never envisioned.

          The Morse Taper was designed for low spindle power and easily machined materials. Originally, it was provided in six sizes, 1 through 6. Number 0, stub and 1/2 sizes were added at later dates. Each original size was designed to handle a specific size range of drill, and as the drill became larger, holding power became reduced. For this reason, it is not good practice to use increasing adaptors when driving drills. A lathe with a MT#2 tailstock will comfortably handle most smaller drills with MT#2 shanks, but using an MT #3 X #2 or #4 X #2 increaser without mechanically restraining it externally is asking for problems.

          Today's drills are frequently selectively hardened, the shank being drawn back to a lesser hardness than the cutting flutes. This is done to maintain a sufficient hardness on the cutting edge while not making the shank brittle. The process and degree of hardness will differ according to size and manufacturer. There is not one statement that will fit all cases.

          I find it interesting that Millipore will lock threads on PM that offer meaningful discussion on imported tooling, but come over here and interject his own meaningless comments on the same thing.
          Jim H.

          Comment


          • #65
            Originally posted by Evan
            Ahem, I gave a known standard, a taper that fits correctly. That is all you need to compare to. That is also all I needed to make a #2 MT last night that fits correctly.
            Somehow, my comments were posted before I finished. You merely made a taper that fit your tailstock. That is a simple operation. My comments are directed toward determining if a given taper is in spec. While it might fit your TS, that is not a standard.
            Jim H.

            Comment


            • #66
              If anyone cares to refute the purpose of the tang, I request that he provide as least as many documented references stating that it's only purpose is to expel the drill.
              I didn't say that, did I? Also, exactly how does the quantity of references make them correct rather than just common belief? That is a frequently used logical fallacy. Just because "everybody" thinks something is so doesn't make it true. I showed you evidence of what can happen if the tang is needed to drive the taper in the event of poor tool holding. Now it's your turn to make me believe that Morse intended that as a normal mode of operation rather than a protection against damaging the spindle. Having to rely on the tang to drive the bit means the machine and/or bits are worn beyond normal operational standards.


              While it might fit your TS, that is not a standard.
              For my purposes it is the only standard that matters.
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              • #67
                You merely showed a twisted tang that was a result of some form of misoperation.

                Four acknowledged, documented sources is far from "common belief". If your opinion is that the function is any other reason than I have presented, supply documentation to support that.
                Jim H.

                Comment


                • #68
                  Originally posted by JCHannum
                  You have since made an attempt to measure them, in your own words; "a close rough estimate". Measuring a taper with a micrometer with flat faces is very difficult. It is not a problem on the large end if there is a sharp break, but the small end is problematical. It is also very difficult to locate the exact point where the measurement is made, and difficult to measure the linear distance between the two points. This is what I referred to. Truly accurate measurements will require some rather complex setups, probably a sine bar, Jo blocks and a height gage on a surface plate is the best setup for the home shop, and I agree with you that the exercise is not worth the effort.

                  Holding two Morse tapers together as Evan describes is of little use, as it merely tells whether they are the same or different. Again without a known standard, it is not much use. As you pointed out that method has it's own inaccuracies.

                  I am not picking on you (maybe I am a little), but just trying to point out that some things are not always as simple as they seem. I don't know if the Indian taper is out or not. It probably is, and the Bison probably is very close to ideal. For most applications, the Indian taper is probably acceptable, for yours, it is not.
                  Good points.

                  Let's see if they stand up.

                  The "attempt" was pretty successful, I believe. Here's why.

                  The error was determined to be about 0.007. What would it take to get that error, in terms of a position error on the taper?

                  At 0.599 per 12", it takes about 0.120" position error along taper to get to 0.006 error of diameter. That seems pretty large, I think I can (almost anyone can) do better than that.

                  I will allow an error band of 0.05 on length, since I made a legitimate effort to hit just visibly "ON" the ground area above the tang, which has a machined 'step".

                  I will agree that I can't, therefore, be sure within 0.002 or so, of the ACTUAL taper.

                  But I will NOT agree that I cannot be sure *within the measured error* or more, that the taper is WRONG. IOW, I KNOW it's wrong, but not exactly how much, since my measurement is more accurate than it has to be to cover the observed error.

                  They might be outside the tolerance by 0.002, or might be outside by the 0.004 I suspect, or it might be outside by a full 0.006 (0.002 over my measurement). Actually less, since the 0.05 is the probable "band" and not the +-.

                  yes the two tapers is probably of less use than making a two point gage with two sharp edges with a known space between, and locating them a known distance apart.

                  Without a known standard, all the objections you brought up to a fit comparison are in play. There is, again, no info other than "these don't match" which was known to begin with.
                  Last edited by J Tiers; 02-10-2008, 05:59 PM.
                  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


                  • #69
                    Originally posted by JCHannum
                    As far as Morse Tapers and the purpose of the tang, I have presently four sources that identify the tang is to drive or share the driving of the drill. These are three text books and one manufacturer's handbook as follows:

                    "Machine Tool Operation" Henry Burghardt 1919, Part 1, page 142
                    "Bendix Cutting Tool Handbook" copyright 1972, page 169
                    "Machine Tool Operation" 1959 Burghardt, Axelrod and Anderson, pp 175 & 176
                    "Metalwork Technology and Practice" 1975 Ludwig, McCarthy and Repp, page 483
                    My machinery library is almost complete -- I have three of those four books

                    From the 1959 Burghardt

                    "The purpose of the tang is to help drive the drill, since the hold of the taper alone is not sufficient."

                    ...and for Evan:

                    "It must be understood, however, that the tang alone is not sufficient to drive the drill or other cutting tool, and consequently, the taper shank and hole must be properly fitted, clean and dry, and the shank must be firmly driven home or the taper will not do its share, and the result will be a twisted-off tang."
                    "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                    Comment


                    • #70
                      That does not explain how I am able to drill large holes in steel with MT3 drill bits held in the headstock taper of my lathe. No tang driving and no drawbar. Still works though. The tang isn't needed if the equipment is in good shape. That convinces me that the purpose isn't to drive the bit. Those quotes are not convincing as experience proves them wrong. I am not offering an opinion, just my experience using this sort of equipment over the decades.
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                      • #71
                        If ANY of youse guys had ever had to dig a center out of a spindle, you'd no longer attempt to convince us that the taper can't hold the drill etc.

                        I've had to step drill out, and then chip out, a center from a morse taper. No amount of axial knocking and banging that we were willing to do to the spindle worked, that thing was in to stay. We even took out the spindle and tried freezing, heating (as much as we dared) etc. No dice.

                        It is particularly important that it was a CENTER, since it COULD NOT have been spun in the taper, as a drill etc might have been. (and it had not been, it was known to have been forced in hard.)

                        After the bulk of the material was removed, tediously, the case hardened shell of the center popped out suddenly. No particular galling or roughness was visible. Therefore it wasn't "spin-welded" in, it was just plain stuck.

                        Quite clearly it is possible to get a taper tight enough to resist even a heavy axial impact in the "removal direction", let alone a turning force.

                        As far as authors and their opinions, authors used to deny gravity, state the earth was flat, etc. Writing maketh not truth, truth is self-evident when examined with an open mind.

                        I have no doubt that the tang CAN drive, to some extent.

                        But SHOULD it be ALLOWED to drive the drill?

                        The tang is normally only perhaps 2/3 of the diameter of the taper. It may be substantially smaller than the drill diameter. Not a good start, lots of leverage against it.

                        With an MT2, you can get a 3/4" drill, but the tang is only 1/2".

                        Then also, in order for the tang to drive, the taper must have slipped more or less, since the tang slot is considerably larger than the tang thickness. it is unlikely that the shank was inserted with the tang tight against the "driving surfaces"....

                        If the taper has slipped, it's friction has dropped a LOT, the tang will take a goodly impact, and will have to bear most of the force of driving the drill.

                        Since drills can be held by the friction of three small jaws on a straight shank, at or below the drill diameter, I would be confident that a taper of a larger diameter than the drill would easily be able to hold the drill, if knocked-in solidly.

                        Now, there ARE key-drive tapers. And there are Collis drill-holders for tanged straight shank drills,

                        The tanged drills have a tang at the same diameter as the drill, and the tangs are a fairly close fit in the holder. That is at least 30% better than the tang on a taper.

                        Keyed tapers:

                        American Standard nose key drive with drawbolt, self-holding tapers......

                        same taper as morse, but has keys on the spindle face, at a larger diameter than the taper gage line (good leverage). No tang, uses drawbar(ASA B5.10-1963)

                        American standard taper drive with keeper key, self-holding tapers.

                        Same as morse, with a key driven in through the socket and shank crosswise. Still has the tang, no drawbar, the key holds in the shank (and won't let it turn, BTW). (also ASA B5.10-1963)

                        I have left out the 40 taper etc, as they are intended to NOT be a "holding" taper.

                        Then Evan brings up a good point, that many T/S rams have no tang slots, yet they drive the drill quite well at large diameters.

                        Drills with twisted-off tangs will still be usable if the tapers are OK, and I have drills with no tang which work well, drive just fine.


                        My conclusion based on experience, as well as on the geometry of the drill and tang is that:

                        The tang is indeed "geometrically able" to drive the drill, in that it has a physical interference which will in fact put a turning force on the drill shank.

                        However, one would be far wiser NOT to let it do so, but rather to make the taper do the work, since the tang is usually soft and relatively weak.

                        The friction of the taper and socket is fully capable of doing all the driving if correctly installed in an undamaged socket.
                        Last edited by J Tiers; 02-10-2008, 08:24 PM.
                        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


                        • #72
                          Originally posted by Evan
                          That does not explain how I am able to drill large holes in steel with MT3 drill bits held in the headstock taper of my lathe.
                          You have a light-weight hobby lathe. The machine texts JC posted are referring to industrial machines.
                          "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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                          • #73
                            Originally posted by J Tiers
                            Then Evan brings up a good point, that many T/S rams have no tang slots, yet they drive the drill quite well at large diameters.
                            Many tailstock rams have no tang slots?

                            I thought most lathes with MT3 and up tailstocks have drive slots? I know the Clausing 5900's and 6900's do, and most (all) of the Monarchs.

                            The 10EE, for example, which uses an MT2 tailstock, has two hardened setscrews in the tailstock spindle that engage the tang, preventing rotation of the chuck or MT2 drills. The fact that Monarch put those tang capture screws there is another clear indication that the tang is intended for driving...
                            Last edited by lazlo; 02-10-2008, 08:40 PM.
                            "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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                            • #74
                              You folks are welcome to operate your machines in any way you see fit. If asked for advice, I will pass on that of acknowledged machine trades instructors and tooling manufacturers. If the Morse Taper were such a powerhouse one must question why it sees such little application in the real world.
                              Jim H.

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                              • #75
                                Originally posted by JCHannum
                                You folks are welcome to operate your machines in any way you see fit. If asked for advice, I will pass on that of acknowledged machine trades instructors and tooling manufacturers. If the Morse Taper were such a powerhouse one must question why it sees such little application in the real world.
                                Probably because it is a pain to install and remove.....

                                When "in" well enough to drive effectively, it is hard to get back out.

                                The 30, 40, or 50 taper have tang drive and easy removal.

                                Morse and the B&S tapers DO get a lot of use, though...

                                And, BTW, the drawbar in a drawbar-held taper does not do *one thing* to prevent rotation. And if there is a drawbar, there is NO TANG.

                                Yet drawbar-held tapers drive large milling cutters...... and do not slip much, I have never had it happen although I have had arbor keys sheared through.

                                "Well", you say, "they are held in solidly". And that is true.....

                                But of course the only resistance to ROTATION is due to friction...... the drawbar merely ENSURES the existence of that friction.
                                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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