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  1. #1
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    Default Chuck grinding recommendations

    Hi guys,

    I’ve got a large Jacobson surface grinder that I need to chuck grind. Before I go in and pull the wheel in to the chuck then spend half a day flattening it out... I know people love to give their opinion so let me have them!

    I’ve only ever done smaller grinders with 1/2 inch wheels, this grinder has like 1-1/2, 2 inch wide wheel
    It’s an auto down feed with incremental and continuous cross feed.

    What’s everyone’s strategy?

    Rough dress or fine dress on the wheel?

    Depth of cut?

    Spring cuts?

    Flood with coolant?

    Anything else?

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    I did not do one that big, 1" wide was max. However I think that the procedure is not much different. Before grinding I do run a dial indicator across the chuck to find the highest and lower spots. When grinding I start with the wheel just touching the high spot and go down from there to the lowest (sometimes I run a series of felt pen lines across the chuck to see the progress. Very light cuts, in most cases the amount to remove is very small.
    I dress the wheel with a diamond and do not stop the machine after dressing - going right to grinding. Using coolant for dressing and grinding. Some suggest using little lower speed (or smaller wheel) for truing the chuck. I installed a variable frequency drive for the spindle motors on my grinders and did run the wheel little slower in one or two cases, though I did not see much difference.

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    If you have any doubts, slap a bit of mild steel on there as near to the size of the chuck as you can find and have a practice go!

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    I like to use a 46k as perhaps the hardest and finest grit..courser / softer and larger grit even to a 32 OK...But with using what you have before then Ok.
    Agree with Wlodek to map the chuck to know where likely to hit first .might put on a slip of tape to see I am .002 off the high place.
    When getting near a full clean-up potential for heat burn is high so might give a little pause time at off chuck on the ends.
    Like to warm up a bit so with long travel auto feed might let machine warm for 5 minuets or so.
    Like to grind wet even if needing a hand spray bottle.
    and with mag on..
    like to break the follow wheel edge with hand hone a radius or bevel to that edge.

    If it has been some time since last chuck-off might take chuck off and give a hone and grease or oil clean up there. and re tighten with only 3 fingers with standard length wrench. Being sure the wheel will clear the mount location.
    Last edited by michiganbuck; 04-18-2019 at 08:13 PM.

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    In another thread I was advised 15 ft# on one nut and 10# on the other side. This was from Walker spec.

    Dave

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    Quote Originally Posted by Wlodek View Post
    I did not do one that big, 1" wide was max. However I think that the procedure is not much different. Before grinding I do run a dial indicator across the chuck to find the highest and lower spots. When grinding I start with the wheel just touching the high spot and go down from there to the lowest (sometimes I run a series of felt pen lines across the chuck to see the progress. Very light cuts, in most cases the amount to remove is very small.
    I dress the wheel with a diamond and do not stop the machine after dressing - going right to grinding. Using coolant for dressing and grinding. Some suggest using little lower speed (or smaller wheel) for truing the chuck. I installed a variable frequency drive for the spindle motors on my grinders and did run the wheel little slower in one or two cases, though I did not see much difference.
    I thought about running an indicator before and after just too see, the grinder runs pretty smooth and the chuck isn’t badly dented so hopefully the needle won’t just shake really bad, my only concern is that it will give a false reading as it will be testing the flatness of the ways aswel.

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    Quote Originally Posted by Luke.kerbey View Post
    I thought about running an indicator before and after just too see, the grinder runs pretty smooth and the chuck isn’t badly dented so hopefully the needle won’t just shake really bad, my only concern is that it will give a false reading as it will be testing the flatness of the ways aswel.
    One cannot test the flatness of the ways by indicating the magnet
    A camelback on the magnet can give you a idea
    Peter

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    Like perter said ,you might check with a dead true flat something to see if the unused area of the last chuck grind ground flat..But you can't do anything about that with not rebuilding the machine ways..A good test if looking to purchase a machine.
    Grinding the top of chuck likely will make it right or best it can be.
    Worst enemy is the chuck getting warm and expanding so when it cools it is out of flat.
    Getting hot enough to make a burn line..then the chuck is in very poor shape.
    Grinding a chuck that had/has corrosion under then will/may be better but not best.

    Some say grind the pad, the chuck bottom and then the top..I don't do this, except if I have rescraped the machine.
    I just hone the pad with a new or known flat stone (very even figure 8s), hone the pad (8s) grease or oil the pad and put it together with a 3 finger pull. Yes you can torque wrench it if you wish.

    With not having an indicator you can tickle a small part setting at far right corner chuck nearest to you with noting the down dial number, kill/stop the spindle, then hand feel that part to the wheel at center back-rail and a few other places about the chuck marking -1, -3, -2 what ever it is low in places. At reinstalling be sure the chuck hold downs are stout enough to not bend and pushing deep set in the step so not pushing the outer edge....perhaps 10-13mm or better. Be sure the hold down bolts can freely hand turn past the needed amount.

    oh, I keep a tab of line marked tape so if I should have to walk away and lift/move a hand wheel I use the marked tape to the hand wheel so that number can't be forgotten. Knowing what you dresses this can tell where you will hit.. perhaps .002 past tape line.
    Last edited by michiganbuck; 04-19-2019 at 10:51 AM.

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    Quote Originally Posted by michiganbuck View Post
    Worst enemy is the chuck getting warm and expanding so when it cools it is out of flat.
    Very true. That is why I prefer to use a permanent magnet chuck for precision work. When truing an electromagnetic chuck I switch it on about 20 minutes before and run the machine with the coolant as when grinding with the wheel very close but not touching. Then I lightly dress the wheel with the diamond (it is located above the wheel in my grinders) and proceed. This procedure gives good results, but even then, when a work-piece is attached the heat distribution pattern is different and a small error possible. With an electromagnetic chuck and a 200mm x 200mm (8" x 8") work I was never able to get better results than +/-3 microns (little over one tenths) while with the permanent magnet about twice as good. This is on a well maintained Jones & Shipman 540X surface grinder. By the way, I follow the same 20 minutes warm-up with coolant for precision work.

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    Hey, so the company I work for runs all okamotos, 12x24 to a 28x60 and we've called in the technician a few times. Well i learned to dress from two techs who did it identical ways. First and foremost stable atmosphere, no opening garage doors near it when there's a big temp difference, we have a grinder near a window and we won't dress the Chuck when the light hits it, which is usually quitting time anyways.
    1. Rough dress the wheel to minimize part adhesion and heat
    2. Magnet on so it's in the natural clamping state
    3. 50 mil to 1tenth indeed to reduce heat
    4. No spring cuts also minimizes heat
    5. Flood the thing in coolant
    Now I can't say this is a fool proof way of dressing, it's just how this particular company dressed all brands of Chuck's they encounter.

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    I like to do a final dress on the wheel at 10Hz
    for a nice open free cutting face.

    -Doozer

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    Quote Originally Posted by Sjzona View Post
    Hey, so the company I work for runs all okamotos, 12x24 to a 28x60 and we've called in the technician a few times. Well i learned to dress from two techs who did it identical ways. First and foremost stable atmosphere, no opening garage doors near it when there's a big temp difference, we have a grinder near a window and we won't dress the Chuck when the light hits it, which is usually quitting time anyways.
    1. Rough dress the wheel to minimize part adhesion and heat
    2. Magnet on so it's in the natural clamping state
    3. 50 mil to 1tenth indeed to reduce heat
    4. No spring cuts also minimizes heat
    5. Flood the thing in coolant
    Now I can't say this is a fool proof way of dressing, it's just how this particular company dressed all brands of Chuck's they encounter.
    What is spring cuts?

    Good post Sjzona,
    Also wheel grit size and hardness is important to mention.. 32-40 grit is Ok/recommended, 46 at the very smallest grit. H to K hardness is good for any chuck grinding grit size...
    (Some shops use a 32 grit wheel) as avoiding a burn is most important.

    I like to hand feel the parked wheel to the least used chuck area, perhaps the near-side of the chuck to know that spot is likely the touch-off place. Raise up .003 (go a half turn up then come back to -.003) and with a parked wheel travel over the chuck to see there is no wheel-touching of the chuck.
    Use incremental cross feed grinding, only going/starting from one side(the front), with a set down dial of -.0005 -.001. from the last cross..and perhaps -.0000 -.0001 for the spark out..* Wet, even if one needs to use a hand spray bottle and soapy water.
    Down feed grinding will most often burn a Chuck. Yes I have ground dry but I am a grinder hand with many chuck grindings under my belt. Likely many a new guy will have trouble even wet. The apprentice says "It was going so good I thought I could go faster."

    *Qt Sjzona: [we've called in the technician a few times.] A very good idea to do that because a poor grind/burning can ruin a chuck. it might takes years or never be made right.

    note,
    Richard the SG book is over 20k words in, and not yet done..likely I will look for someone good at drawing from my sketches for that part..perhaps a PM guy.

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