Surface grinding marks, any ideas?
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  1. #1
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    Default Surface grinding marks, any ideas?

    Attached is an image of the marks left by my surface grinder. Does anyone know the problem and a solution?
    Attached Thumbnails Attached Thumbnails grinding.jpg  

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    looks like your wheel is clogged.

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    Wheel has slipped on the spindle . . . tighten the wheel adaptor and the spindle nut, then dress the wheel.

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    The wheel does show clogging, so I dressed it, again, with similar results. Could the wheel be contaminated in one sector that makes it clog? I tried another wheel, 32A60-G8VBE, dressed it, and had similar although not as bad results. The first wheel was a 5SG46-GVSP.

    I don't think it slipped as I have a large diameter arbor and had it quite tite.

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    Quote Originally Posted by laminar-flow View Post
    The wheel does show clogging, so I dressed it, again, with similar results. Could the wheel be contaminated in one sector that makes it clog? I tried another wheel, 32A60-G8VBE, dressed it, and had similar although not as bad results. The first wheel was a 5SG46-GVSP.

    I don't think it slipped as I have a large diameter arbor and had it quite tite.

    Unless you have a soft start of some kind, it slips everytime you turn it on. Maybe just a little but it does. That looks like a loaded wheel or very hard. The wheels you list are soft so probably not the bond. However the two wheels you list are very different and what works for one does not apply to the other. Dress it clean and dress the sides, might have a bit of a wobble to it. Once dressed, do not turn it off until you are done with it.

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    Spray the wheel with Dykem and when you dress dress fast and .002" deep. If you dress back and forth with no feed down...the wheel gets dull. Also your diamond might be dull. How to Dress and Balance a Surface Grinder Wheel - YouTube

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    Guess you should post more info:
    Machine and this wheel spec. normally grinds a good finish.
    What material
    what size and make of machine.

    I would say the diamond not sharp, 2. The wheel slipped on the mount, 3. Coolant logged or some other way wheel out of balance, 4. the wheel too hard and bouncing, 5. The feed is too Fast. 6.the wheel too soft and can not penetrate the part hardness, 7. The work not hard set on the chuck because of a warp-up part or hole in chuck, 8. the wheel lead face wobble to be slapping the work caused by bad blotter or mount. 9. the wheel mount not fitting the spindle taper 10. The finish so very good THAT it looks poor 11. the motor or spindle bearing going bad. (always blame the machine last)

    Blue in your mount to see it hits the spindle taper correctly, a couple magic marker line will do.
    Check that back mount face is running true. Set the wheel in an always-set like a line on the mount, a mark at spindle end and a line on the wheel blotter. Spin the mount nut when empty to see it goes easy past the wheel width, Make the wheel mount nut two hands tight (hand on the wheel and hand on the wrench)with about a 6 or 7” wrench then set on a block and make a little tighter with tow hands holing. Have the diamond holder hold the diamond at about 10 to 20* to the wheel and the holder base turned perhaps 30* left so the diamond is in a slight drag position. Turn the diamond about 1/8 turn in the holder. Have a 3/8 or better diamond shank held short. Dress across with a last pass having down and then lift off wheel with not a no down follow back..

    Also consider the looks of a surface finish can be deceiving as being so very good the rotation lines always there can begin to show up more to make a finish appear poor. With that one can need a courser wheel so rotation lines do not show. This so making the finis not reflect light so easy.

    Have you tried a white wheel on that part perhaps an AO 46 j or k? Norton is an OK wheel but you might try the Radac white or pink wheel in a 46 j or k some day. But chasing wheels is often not as good as trying different grinding Techniques.

    I had some CPM material that I could not get a good looking finish (much like yours) so made a last finish, two straight swipes on a plate with some medium paper. Can't remember but might have been 220 crocus. Yes my steel ground plate not my surface plate...Also finished many jobs on a lapping plate, some to make flat, some smoother and some rougher.

    I have a current job that I finish with Norton Diamond paper.

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    It's hard to decipher the scale of the picture.
    If the table rides on roller or ball bearings, I'd also suspect brinelling of the ways.

    Paolo

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    This same or very similar question has come up here many times in the past. (I had the same issue with my SG BTW when it was new to me.). The most common (seems like every time) root cause happily has the simplest solution---tighten your wheel on its adaptor. Otherwise it slips around after truing. Once I learned to use two of those 8 inch or so standard pin spanners with the one on the inside of the wheel stopped from rotating by bracing it against the table or vise etc and then really bearing down on the outside wrench, all such problems have disappeared. Sure, a loaded wheel can also cause problems etc. but don't even start thinking about bearing issues etc until the basics are covered. And don't ever forget to use blotters inside and out.

    BTW, no soft start (wish it did) on my machine and no slip issues either.

    Denis

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    Adding to Dennis's be sure the paper gaskets (that help the wheel from spinning) are between the wheel and flanges. Also I find dull diamonds to be a major issue too.

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    LOL

    Richard recommended spraying dykem on the wheel. Spray will work, I guess.

    DO NOT brush it on. The wheels are porous, and will soak up a fair about of the Dykem if you brush it on. When you turn the machine on, you will have a blue line around your room. I did it once with a tool and cutter grinder without a guard. It was a complete strip 360 degrees around! At the time I thought I was being so smart :-)

    Vince

    P.S. I use a large Sharpie now. Just 8-12 marks across the wheel, evenly spaced.

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    The machine is a Taft Peirce 5-10. All the ball and roller ways have been either ground, at a friend's shop with a big grinder, or lapped with a round diamond charged lap the same diameter as the balls. The spindle is very smooth. The chuck was recently re-ground.

    The parts were 4" long Snap Jaws, not full hard but not soft. It does not appear that the marks are from the roller ball bearings as the pitch is about .090" in the image and can be varied in pitch by speed of the table.

    Yes, the surface is very flat as checked on a plate and with a reflection. It is more of a cosmetic issue.

    The flange I used is a 3" diameter versions and blotter papers are used.

    I will check through the suggestions today or tomorrow and report back.

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    Looks like an out-of-balance wheel hitting once per revolution.

    If this is a small grinder 6x12 or so it probably does not have provision for balancing. Following the advice of others:
    1. Use blotters. Without blotters wheel could crack on tightening.
    2. Make sure wheel nut is very tight--It could be flipping off center upon start up.

    3. Grinders that are belt driven or VFD may not flip the wheel off center at start up (i.e.--slow start). Direct drive could cause problems because of the fast start.

    Additional stuff:
    1. If you have a balance arbor and stand --use it. Ebay has them.

    2. The wheel hub (1-1/4 hole, probably) is always a sloppy fit to the grinding wheel. Usually loose by .002/.003 inch. This sloppy fit gives the grinding wheel room to flip off center and cause both unbalance and grinding on one section of the periphery of the wheel. My solution is to place scotch tape on the hub--a bit at a time until the hub and wheel have a snug fit.

    3. Dress the wheel on OD and also on both sides as far up as you can go. I have seen wheels that are poorly made and the sides are not parallel, giving a out of balance condition.


    Lost

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    OK, the diamond was dull on its spot of presentation. I rotated it to a sharp point and it did seem to help. The surface is much better but still does not have that Hermann Schmidt finish. I did check the balance and it is off a bit. But my 3" adapter does not have sliding weights so that is on the buy list next week.

    If dressed in the unbalanced condition, should it still give a nice surface? Or does it set up a resonance and makes the wheel vibrate in an unpredictable way?

    I always use blotters and do dress and grind without stopping the spindle. When stopped and re-started, the surface is the same so I do think I am tightening enough.

    Attached are images after all the above.
    Attached Thumbnails Attached Thumbnails grinding-2.jpg   grinding-5.jpg   grinding-4.jpg   grinding-3.jpg  

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    Quote Originally Posted by laminar-flow View Post
    <Snip>

    I always use blotters and do dress and grind without stopping the spindle. When stopped and re-started, the surface is the same so I do think I am tightening enough.

    Attached are images after all the above.
    Could be. Or could mean the wheel moves every time. Have you tried "overtightening" it?

    Denis

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    Sure looks much better.
    Was that a no feed finish pass? a 0002 down feed? How large are your cross step over? how fast your travel? might you blue it up (Magic marker strips OK)and take spark our to see if spark out is taking any stock?

    I stop and start all the time so anyone with that worry should make wheel tighter IMHO. And pen mark the blotter to know it did not do that, you should know it not turn on the hub every time you start or stop wheel..

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    That was a no feed finish pass with just a few sparks visible. Cross feed is .1 as can be seen in the lines. Any idea why the cross feed lines show up? The ripple might have been partially addressed by the diamond rotating and the rest of the ripple might be balance. Sound reasonable?

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    [no feed finish pass with just a few sparks visible] perhaps the cooling of the part makes the part slightly smaller so the spark out does not take any stock or enough to clean up. ?

    What kind of finish do you get with a fresh dress.. then feed .0001 down feed with no cross feed at all.. pause after pass a three count ar each end..Only down feed on the grind side. Long travel very slow...grind this slow way until you clean up the marker strips. look at Finish and note.

    Now add some .050 cross feeds only on the grind side still slow long travel. and three count... note finish

    Next cross on both side still .050 Cross and a three count.

    Next make your normal cross and travel speed. feed both sides.

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    Quote Originally Posted by laminar-flow View Post
    The surface is much better but still does not have that Hermann Schmidt finish.
    Before i had the jones and shipman 540 i had a old eagle surface grinder, the thing was a heap of shit, literally worn out junk, but it could grind to a damn near mirror finish all day long, literally perfect miror smoothness, ok it ground so much curve in parts you could easily measure it with a 6" rule, but god what a finish. I have never ever got the J&S to grind close to that in anything :-( Probably gotta buy it a new spindle to get close!

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    When I really slow down, a 4" pass in 4 seconds, the ripples get real small and faint. Faster shows the ripples. The lines from cross feed are still there, distance apart depends on the cross feed distance so that matches up.

    When going faster, it does seem to leave less ripples with a heavy feed, about .0003 or .0004 per pass. When passing back over with no down feed and it only take off .0001 or so, the ripples show more.


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