Surface grinding marks, any ideas? - Page 3
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  1. #41
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    That makes a lot of sense: the pattern is due to resonance frequency vibrations. As mentioned earlier, despite I'm completely ignorant in grinding, I suspect that the issue is with the table. Obviously, it results in movements at the chuck below detection limits (at least when the spindle is still and not grinding). But at the edges of the table/saddle the deflections could be on the measurable range.
    If the machine had traditional ways, the oil film would be plenty enough to damp them and any false contact could be tested with a blow hammer tapping on different places on the ways to feel (judging by the sound) if there is good contact or there is a slight gap.
    In machines with ball or roller bearings, I'd be obviously more hesitant in doing so. Maybe, it is worth doing it by pounding with the hand and listening with a stethoscope.

    Paolo

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    Wheels can be carbide drill indented for balancing (HSS drill likely would work OK), actually crushed with the drill not even need be sharp. Yes the ring test proves the wheel still good and one can loose (crack) a wheel doing that(but not often). Wheel best set on a flat board and hand or drill press drilling. A mount up should line be pen-marked on any and all wheels so one can put them back on the mount the same way up.
    *Do check the wheel head is solid fixed with an indicator set and a hand push this way and that.. That the spindle has no end play…
    As Richard pointed out a sound check… you can also do that with a steel rod touching the spindle and then to you closed off ear. (push your ear lobe over the ear hole and hold the rod tight to the spindle at each end at starting, running and coasting to stop...
    Check the wheel front face is verticl square with the chuck using a precision hand square or a parallel off a 123 block or angle plate.
    Check that the fresh dressed wheel touches the the already ground part squarely with wheel front bottom and back bottom just marking blue with long travel and down feed increments of .0001 with using no cross feed..Just down on the part, with an off part wait time at each pass. Then when you get a just touching blue begin cross travel. first in cross ,then out cross to see if there is and change..*Yes pause off the part for a wait time so no heat part expansion is included in the test.

    A bad motor bearing or the motor to spindle mechanism can cause a vibration you can sound test or hand feel.

    How good is the fresh dress wheel, with only the 0001 per long pass down feed, with off part pause wait time and no cross feed finish? showing the marking or not?

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    interesting thread. what do you think about this?



    fotos kostenlos

    foto hochladen

    the piece is 40 mm, around 30 hrc and the pattern is measurable, around 0.5 mu in depth. dont mind the scratches, they got there later. its on a small hydraulic oil way grinder, dry.

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    Looks like the worst of the issues I had. Is your wheel showing darkening in several spots around the cutting surface? Do the marks vary in pitch if you feed slower or faster?

    --or--

    Flip them over, oven on 450F, butter and garlic. Looks like scales.

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    Give up or still trying?
    By now you should have.. Sound tested the spindle bearing – run a long-travel only grind- one hand shove all grinder parts to see anything loose- tried a balanced wheel- tried cross in and out going to see any difference- run a tenth indicator over a chuck held flat parallel- test to feel any end play in the spindle- check the wheel is vertical square and angle square to long travel- made sure the wheel is tight-be sure the machine is well set on the floor and level- check for wheel face wobble- what else did we suggest?
    You might get a white wheel and take it with mount and pay a local grind shop to balance it.

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    Hi Michigan, Yes, I have made some progress in that most of the issues are from the diamond, as you suggested. It just didn't have many points. I located the pointiest point on the diamond and that made the biggest difference. But I did call Norton and the wheel I am using, the 5SG46-GVSP, was designed for heavier cuts and would have issues with light cuts.

    I was preparing for a presentation this week for yesterday and have been busy too. I might have some time tomorrow to try some older, but different wheels. Balancing by drilling the wheels as you suggested.

    I will also order some new wheels today.

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    Pacific Northwest... could be earthquakes..? wait until the floor seems to be staying in one place.

    I did work in a shop where a big press would shake the floor enough to mark the grind...

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    well, this is the worst piece i could find and i tried to make as bad a picture as possible (200x). this is another one (hardox 45):

    foto hochladen

    there are no spots on the wheel and i also have no idea what wheel it is. i use the machine sparingly for shims etc. and if somebody tells me its the bearings, im going to leave it alone. the spacing of the marks is much wider that the frequency of the wheel as i go very slow.

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    Put your 32A wheel back on and dress it the same way. the 32A is a very good general purpose wheel and you should be able to take light cuts with it.

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    Well, I might have found the issue. I put my spare spindle, which is actually a bit louder when running, on and it has improved the finish quite dramatically.

    I took the old spindle apart and the bearings were arranged as such. The front pair are arranged back to face, as it the rear pair and both pairs oppose each other. The rear pair have a spring loading the outer races. In talking to a rep at Barden, it looks like the front pair should be back to back to constrain the axial and radial forces much better. This makes sense since both the OD and ID races are clamped on the front pair by the wheel. The rear pair can remain back to face since they are loaded with the spring pack.

    I am suspecting that the spare spindle I have might be that way.

    This is a Taft Peirce spindle so if any has any original documentation that shows the bearing arrangement, that would be much appreciated.

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    Quote Originally Posted by dian View Post
    interesting thread. what do you think about this?



    fotos kostenlos

    foto hochladen

    the piece is 40 mm, around 30 hrc and the pattern is measurable, around 0.5 mu in depth. dont mind the scratches, they got there later. its on a small hydraulic oil way grinder, dry.

    sorry, no idea what happenen to my links in the meantime.

    this must have been it:







    (last one is blued up.)

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    so is anybody ready to venture another opinion on my pictures? this is the worst result that i ever had and i saved the piece for reference. there is no visible burn and the pitch varies with table feed. i dress fast with new diamonds, either overhead or off the table. grinding dry or with spray bottle, makes no difference. as mentioned the dips are measurable, about 0.5 micron (probably less). i think its the bearings.

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    If you long travel with slow hand wheel feed and .00001 set down feed with coolant and your fresh dressed 32a 60. then hand wheel cross with being off the part 2.5mm and slow hand long travel again what finish do you get? This may take harmonics of auto feed out of the test and narrow it down to balls, spindle or wheel.

    I don't think it is wheel slip but the wheel should be as tight as you can make it with one hand on the wheel and one on a 6 or 7" long wheel wrench.. then set your wrench on a stop block and with two hands make it just a little tighter. (be sure your wheel holding nut nut travels by hand past the place where it tightens the wheel.)

    If I was there I would hand travel (with a fixture) a piece of steel on an oiled base with the table and cross not moving but with you never doing such it would be too dangerous for you to try this. this to rule out the balls and narrow it to wheel and/or spindle.
    Having a small tool post grinder one could clamp that to the spindle head and take a test grind to prove spindle good or bad.

    If you stop over a well sparked out part and hand push/pull/bump the spindle head how much sparks might you get?

    With a fine finish parallel or the like on the table and long traveling under a tenths indicator how smooth is the long travel? Do you see the/any .5mm bounce?

    With indicator to side of parked wheel head and push pull left and right how much indicator move do you see?

    indicator on the parked wheel mount do you see and movement with hand push/pull bounce the wheel?
    Last edited by michiganbuck; 12-19-2018 at 05:43 PM.

  16. #54
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    I have taken the motor off one of my spindles and need to get at the rear bearings. The front ones are easy, but to get the rear bearings off the rotor needs to be removed. There is a sketch that I made 25 years ago that shows the rotor removed with threads under it, but I can't seem to get it off this time.

    Does anyone have an idea as to how to get the rotor off? The end of it has an internal hex but I have tried and can't seem to get it off.

    Image attached.
    Attached Thumbnails Attached Thumbnails tp-spindle.jpg  


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