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  • #76
    Originally posted by oldtiffie

    Whether you choose to or not is solely at your discretion, but having said that, I am sure that you don't need me - or anyone else -to tell you that.
    No we have Tiffiepedia for that.

    .
    .

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



    Comment


    • #77
      Originally posted by lane
      All so no one in his right mine is going to copy what some one built because they want have the same junk to work with and they will have to improvise just like you are doing . right bearing are not.
      Full marks and anything off the top shelf for Lane.
      That's it, Improvise with what is available and improve, don't follow the herd.
      There are many ways to do something, not always a right and wrong way, just different ways.

      .
      .

      Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



      Comment


      • #78
        just poking fun at the Evan's claim of measuring 3 micron runout on a South Bend 9
        I guess I will have to make the video. Not sure when, right now I am taking video footage of the moon.

        Regardless of what the spec is for this bearing I was hard pressed to see any difference when measuring to the journal or to the bearing shell. That is how it is.

        You said it wasn't a choice, that it came out the scrap box.
        It was a choice to build with it or not. If I didn't like the bearing the project would wait.
        Free software for calculating bolt circles and similar: Click Here

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        • #79
          "If the balls become hot enough they lose strength and this will happen before the races. When that occurs the material in the contact patch will begin to be deformed enough to exceed the plastic yield limit. When that happens the surface layer of tbe ball will begin to form microcracks all over the surface of the ball. The next stage is that pieces of the surface will begin to break away, a process called spalling."

          Not sure if you are, but it sounds like you might be saying that bearing fatigue is due to elevated temperatures.

          Bearing fatigue failure is from so-called Hertzian contact stresses, where max stress actually occurs below the surface.

          I imagine what happens is that the initial fracture grows to the surface and then the little fragment pops off.

          Comment


          • #80
            Bearing fatigue is temperature dependent. The higher the temperature the faster it occurs and at lower values of load/rpm. Conversely, the higher the load or rpm, the higher the temperature for a given rpm or load.

            It doesn't take a lot of temperature to start changing the properties of hardened steel. Several hundred degrees will make a big difference.

            Of course gross overloading will exceed the material strength regardless of temperature. With steels as long at the maximum stress applied is less than 50% of the plastic yield limit no fatigue will occur at standard temperature.
            Free software for calculating bolt circles and similar: Click Here

            Comment


            • #81
              Originally posted by Evan
              Bearing fatigue is temperature dependent. The higher the temperature the faster it occurs and at lower values of load/rpm. Conversely, the higher the load or rpm, the higher the temperature for a given rpm or load.
              Right, and the amount of preload stresses the bearing as well. With a heavily preloaded bearing, the balls are actually deforming the race as they spin.

              There's a good video I found somewhere showing this -- I think it might be on the Barden "Bearing in Mind" DVD. The rest of the video is pretty lousy (mostly a Barden advertisement), but that part was pretty neat -- I'll see if I can find it.
              "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

              Comment


              • #82
                Originally posted by Evan
                With steels as long at the maximum stress applied is less than 50% of the plastic yield limit no fatigue will occur at standard temperature.
                This is generally true for steels w/ a TS of less that 160 ksi, and only if the surface is polished smooth. If there are stress raisers, or if we're talking about bearing steels in a hardened condition, that 50% figure is closer to 30%..

                Also, the amount of deformation at the ball-race contact point is surprising large, and the Hertzian contact stresses much larger than one would naively expect. This results in ball bearings always being loaded above the endurance limit, and means that they always will wear out due to fatigue-induced spalling.

                - Bart
                Bart Smaalders
                http://smaalders.net/barts

                Comment


                • #83
                  Originally posted by John Stevenson
                  I'll have to tell that to the motor rewinders next time they order another 5,000 bearings as a job lot.

                  "Hey George my mate on the internet says that bearing do not wear, A ball bearing that wears is contaminated with some crap that acts as a lapping compound."

                  I can just hear the answer,
                  "Well then, ask your mate where the crap comes from then when we fit factory sealed and greased bearings and running in a clean environment they are worn after a couple of years "

                  Then ask him if he heard of Brinnell or is that a brand of dog food over there ?

                  .
                  Don't be yelling at me, go yell at the bearing manufacturers, who obviously need to talk to you before they go printing more information......

                  Electric motor bearings are of reasonable, but not high quality..... And as you indirectly pointed out (Brinnell), it is certainly possible and probable, that they get slightly or severely overloaded.

                  Before you get your mind further wrapped up in knots, take a peek at the comments about perfect roundness, etc... as above. Some of the rest I don't agree with, but for sure nothing is perfect. Electric motor bearings are *a little less perfect* than spindle bearings.

                  Eventually, for sure, there will be spalling of the races. After that, there will be WEAR, because the freaking bearing has SUPPLIED ITS OWN abrasives. Just quit yelling and get used to it.

                  OK, so loading definitely affects bearing life. i surely hope THAT won't be disputed, cuz you are doomed to fail if you try.

                  Now WHY would it be that loading affects life? Why.... it affects the time until fatigue of the surface occurs..... due to spot overloading by those micro-defects mentioned. They don't hit the same place every time, but they do over time get a lot of hits on each spot.... roughly proportional to the total number of revolutions, since teh hits occur on any spot at a fairly consistent rate due to the random process.

                  Now, your overloaded belt drive motor.... operating at about 3000 rpm..... in a year of 8 hour days, it completes 288 million or so revolutions...... in two years, over 550 million revs. if they run more than 8 hours, start multiplying that number.

                  I suggest that is perfectly adequate to explain "wear" of bearings in electric motors...... Sheesh
                  1601

                  Keep eye on ball.
                  Hashim Khan

                  Comment


                  • #84
                    If you squint really hard, you can read that the first test on the Sieg chart is testing the runout of the spindle nose. That has a max runout of .04 mm, or 16 thou.


                    Geez Robert ...I'm not trying to be argumentative here.
                    go take a drive to your nearest H F store and bring a DI setup with you and measure a Mini lathe. Report back.
                    I have 3 of these damned head stocks sitting in my garage and plenty of DI's.
                    Think I am imagining this stuff?


                    And,
                    Testbar measurments that are internally located in the spindle have no place at all in this discussion as a method to prove a spindle bearing runout.

                    Steve

                    Comment


                    • #85
                      Originally posted by lazlo
                      Jerry, you said this last time during the Bridgeport spindle bearing discussion, but you still don't get it.

                      Preload, by definition, removes the internal clearance of a bearing by wedging the inner and outer races.

                      Preloading is used to remove the internal clearance of a bearing and is achieved by applying a permanent thrust load in an axial direction. Preloading is used to eliminate radial and axial play, increase system rigidity, reduce run out, increase the assembly’s tolerance for vibration, and reduce operating noise.
                      Yo...... calling Major Robert........... can you hear us Major Robert?

                      I still don't get it?

                      Excuse me, but YOU still do not get it.....

                      As far as clearance, it is ASSUMED that clearance is zero in any set-up system.... one would naturally snug up until that is taken care of...... unless your spindles are *a little different* from others.

                      And it is naturally intuitively obvious to the most casual observer that preload clearly eliminates clearance..... That isn't even a question nor an issue.... it is glaringly obvious.

                      Here is the part YOU do not get. let me know if I use big words that you need explanations of.........

                      AFTER the clearance is taken up..... "preload" applies a good deal MORE force to the bearing. It may be quite a lot of added force.

                      What does this do?

                      Well it takes up a lot of flexibility of the parts INCLUDING INCREASING THE SIZE OF THE BALL CONTACT PATCHES.

                      if you look at a graph of deflection vs force, you will see something somewhat like a horizontal half parabola, taking deflection vertically and load horizontally.....

                      Any clearance is not on this chart. It would obviously be a straight vertical line.

                      OK, so at "low" loads, the deflection increases rapidly, but as the load increases it becomes almost a straight line, with some slope a good deal less than the initial slope.

                      Preload takes the applied load up past the rapidly increasing portion, and into the area of constant slope. The amount can be varied, and may at choice not get to the straight line area. That is a matter of trading deflection vs lowered life.

                      So why do this?

                      Precisely because the slope of deflection vs applied force is LOWER than it is down near the origin, with NO preload. It may be 4 or 5 times less, and every bit of reduction that can be had is good in machine tools. The manufacturer is happy to pay for increased precision with the resulting somewhat reduced life.

                      So, while the effects you mention are true, they utterly fail to describe the true advantage to be had.... The quoted blurb adds the key bit, as well as indeed mentioning the others.

                      The 'runout" mention is a little odd, , it seems they may have a different definition, or perhaps they are considering the reduction in effect of one odd-sized ball or spot due to the loading.

                      But the main effect of preload is a drastic increase in the stiffness of the assembly... the slope of deflection vs load.


                      .
                      .
                      .
                      BTW, preload does NOT add directly with loading....... axial loading increases force on one race, but by deflecting the spindle axially, it decreases force from the race which is applying the preload...... thus removing some preload as actual load is increased.
                      Last edited by J Tiers; 01-02-2009, 11:36 PM.
                      1601

                      Keep eye on ball.
                      Hashim Khan

                      Comment


                      • #86
                        I was just in the shop and needed to switch chucks. I took advantage of the oppourtunity to make some measurements of the spindle on my SB9 using the ultra accurate Tesa indicator. Incidentally, I picked that up at the same time as my horizontal mill. Paid $100 for a box full of metrology instruments including three similar dial indicators by Tesa and Interapid.

                        I am going to make a movie of the spindle runout on the SB, but not to prove a point. With such a sensitive indicator it is possible to see the spindle climb on to the oil film as it is switched on. It takes about 2 seconds during which there are several slow excursions of about 5 to 10 microns either way, not coordinated with revs. Then over the third second it quickly assumes a steady once per rev periodic deviation of about plus and minus 1.5 microns for a total excursion of about 3 microns. This was measured directly on the spindle nose at the register surface. The belt was set up fairly tight and there was no chuck or other load applied. The spindle was set to run at about 180 rpm.

                        It's very cool to watch and it does it exactly the same each time it is started.
                        Free software for calculating bolt circles and similar: Click Here

                        Comment


                        • #87
                          Back to the shop.

                          Originally posted by S_J_H
                          Geez Robert ...I'm not trying to be argumentative here.
                          go take a drive to your nearest H F store and bring a DI setup with you and measure a Mini lathe. Report back.
                          I have 3 of these damned head stocks sitting in my garage and plenty of DI's.
                          Think I am imagining this stuff?


                          And,
                          Testbar measurments that are internally located in the spindle have no place at all in this discussion as a method to prove a spindle bearing runout.

                          Steve
                          You've got it Steve.

                          At this stage the bearing inner and outer concentricity is the issue, but as I guess the spindle OD and internal taper as well as the final cuts on the thread and locating collar will be done on assembly, it will be true to the machine.

                          And that is what counts.

                          I suggest we leave it up to Evan as its his project after all.

                          Perhaps the best way for some to prove or disprove their hypothesis is to get off the side-lines and into their own shop/s, make one themselves and let us know how they get on.

                          Comment


                          • #88
                            Evan. You might want to rethink the spindle nose. Just my 2 cents, but it looks like the perfect opportunity make a D type spindle, or any spidle type thaqt ian't threaded. I only mention it because of the tendancy for a threaded chuck to unwind when in reverse. The tendancy increases with the size of the chuck.
                            I know you said ths wasn't going to be used for threading, but...............sooner or later you know you're going to do it.

                            Comment


                            • #89
                              Originally posted by S_J_H
                              Geez Robert ...I'm not trying to be argumentative here.
                              go take a drive to your nearest H F store and bring a DI setup with you and measure a Mini lathe. Report back.
                              I have 3 of these damned head stocks sitting in my garage and plenty of DI's.
                              Think I am imagining this stuff?
                              I don't think you're imagining it Steve. It's not simple or easy to measure the runout of a machine tool.

                              I don't need to go to Harbor Freight to measure the runout on a 7x10 - I own a 7x10 mini-lathe - it's sitting on my workbench right now. As I posted yesterday, I re-measured it, and it has about a thou runout. Gagetbuilder's 7x10 has a little bit better: 8 tenths runout. If you go to the Yahoo 7x10 group, that's pretty typical, (about a thou runout), and according to the Sieg test report, the 7x10 has a runout spec of .04 mm: 1.6 thou.

                              So your three 7x10's have 5 times less runout than Sieg's accuracy spec, my 7x10, and Gagetbuilders', and most of the machines posted on the Yahoo 7x10 group
                              Last edited by lazlo; 01-03-2009, 10:46 AM.
                              "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                              Comment


                              • #90
                                Originally posted by oldtiffie
                                Perhaps the best way for some to prove or disprove their hypothesis is to get off the side-lines and into their own shop/s, make one themselves and let us know how they get on.
                                Originally posted by Evan
                                So, it appears that the bearing has a couple of microns runout. Thanks for your offer Robert but I don't think I will need that bearing.

                                2 microns = 0.00008 inches.
                                OK, I pulled the Millrite Timken roller bearing I was offering to send to Evan, and measured the runout as .006 micron -- that's 2.36220472 × 10-7 inches! I'll post some pictures later today -- I need to make a lathe with that bearing!
                                "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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