J&S 540 Plain Bearing Spindle - Page 2
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  1. #21
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    Hi Dave,

    Congrats on getting your J&S540 running well. I have a similar machine.

    Quote Originally Posted by small.planes View Post
    Then I put my new 46 grit SG wheel on, dressed it and ground a lovely finish dry onto the block I made to hold my diamond.
    You will now find yourself putting a ground finish on all sorts of things that don't really need it. But its an excellent way to practice!

    Cheers, Bruce

  2. #22
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    Not mentioned here yet But do you have the specified oil for the spindle
    I am not critical about oil in general except on a plain bearing of a grinder

    Peter

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  4. #23
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    The ease to achieve extraordinary accuracy and quick set-up of a surface grinder often lends to moving much work from the mill to the grinder.
    Very often a good grinder hand can out pace a mill because of the less time often needed for adjusting and checking a mill set-up.
    The practice of down-grinding is the fast method for roughing, and then a .003 / .005 or so cross makes grinding very fast...and to know when a part needs a flip-flop to take from two sides..

    For high performance grinding one has to be quick to change the wheel, perhaps going to a 32 or 36 grit to down feed rough-in, and a 46 to 60 (or what) for the finish cross pass..At rough-in it is good to plan that the part will/may heat grow/expand .008 just in case it does. (often it grows .003-.005)

    Also one has to be quick to set the diamond to the wheel..Not travel the wheel to the diamond, often with a swing arm dresser or a dresser clamped to a block..Not sticking a diamond way out or using a super long shank diamond.

    Know and trust blocks to know that clamping to one will give a square or dead right angle part.

    Also good to know to use spotters, and using the diamond height for the spotter.

  5. #24
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    Quote Originally Posted by small.planes View Post
    It grinds, but there is a 'ripple' for want of a better description visible in the finish. I haven't measured it (the surface table is currently inaccessible due to stuff moved to get the grinder running.
    This is 1/10000 cut, taken 2x - once 'cutting' and once 'spark out' (I think that's the correct description)
    Its Gage Plate (O1) that has been hardened. Wheel is a white alox, its mounted, so I cant see the markings, but I think it was a 38 A 46H.
    Cut was taken with the auto feed running quite slow, and the auto cross at ~25 thou. cross feed occurs on both directions.

    Attachment 287401

    I had to dress it with a SiC stone, as my diamond hasn't got here yet.

    I think the ripple might be related to the looseness in the spindle, but this is my first ever grind, so it could also be something else.

    Dave
    Don't fuck with your spindle. All new grind hands with small surface grinders have ripple problems aka chatter etc until they learn how to deal with them. Only when you have learned all these techniques and are certain they don't apply would I go messing with your spindle.

    First, choose a wheel that's correct. I suggest 46 grit, H/I/J/K softness, and open structure. Make sure it passes the ring test. Then:

    Second, make certain your grinding wheel is held tightly. I'm not familiar with your grinder, but on mine there is a wheel adapter that has holes for a face spanner. I lower the head and put the face spanner it then gently turn the wheel until the wrench is restrained by the chuck. Then grab the wheel with both hands and turn it like a steering wheel until it's as tight as you can get it. This will prevent the wheel from moving on the adapter.

    Third, dress the face of the wheel aggressively. Don't take a slow pass across it with the diamond. Zip it across which will leave it very sharp so it will grind cool. After dressing the face, just touch a dressing stone to the wheel corners to break the corner. Then touch a piece of wood to the running wheel to knock off any loose grit barely sticking on.

    Fourth, clamp your diamond block to a small angle plate or whatever you have to, and dress the sides of the wheel from the blotter out.

    On both of the dressing procedures, you must go deep enough to fully true the wheel. For a new wheel, expect to dress off at least .010".

    With a completely trued wheel that is sharp and open, rough grind at least .001" deep, taking not very wide cross-steps. Use a more aggressive traverse speed. For the last cut or two (finish) lower your depth of cut to .0002" or less, decrease your traversal speed and increase your stepover quite a bit. When done, do a sparkout pass with the same speed and crossfeed but with no change in depth of cut.

    Whew.

    Then look at your finish. If necessary, take pictures and come back and post them here. I am a pretty new grind hand myself and the guys on this subforum are great.

    Don't assume it's your machine. And one last word - make damn sure you know how to lubricate your machine and that you have lubricated it before you grind.

    metalmagpie

  6. #25
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    @Michiganbuck,
    I have several sets of feeler gauges from when i used to mess about with cars - setting valve clearances etc.
    Seems like i need too get some chunky bits of stock to make some useful things as practice/apprentice pieces. I'll post some progress as i make it. I certainly need to improve my metrology capability...

    @Peter,
    Yes I have the correct oil for both the hydraulic system and the spindle, the spindle oil is vactra no3 - it's like water. No point in ruining an expensive tool for the want of the correct oil.
    @metalmagpie,
    I already "fucked with my spindle".
    As i noted earlier it had 3 Thou endfloat. Given it is a plain bearing to much endfloat =to much radial clearance. It's 4 bolts (plus some screws for covers) to pull the whole spindle assembly. So i did. Then it was possible to accurately measure how much to much it was and correct the problem.
    If a machine is out of spec odds on it is not going to perform correctly no matter what.
    The almost mirror finish on my diamond holder was 3 thou doc, around 100 thou per pass cross feed. Single pass, no sparking pass. Admittedly i wasn't shooting for a particular size, if I was it might have needed a single dusting pass to get to size.
    With the spindle sorted i have no wavyness in my grinds. Not sure if a 540 qualifies as a small grinder, it's an 18x6 and weighs 900kg/1900lbs.

    I have learning to do, but I've been machining since 2003, so if i suspect the machine i have some experience to guide me to qualify the mechanics.

    Dave

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  8. #26
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    With such a good finish and being able to down feed .0002 and take that amount the .003 you find in end play has little effect. Most likely it is solid in one cross direction and may error .003 in the other cross direction. If finding no way to take that up you just get used to it and make do…Most often to do any precision shoulder step distance you still check with a JoBlock stack (or take measure) because most machines have .002 or better slop/backlash in the cross travel lead screw and nut...

    I wou;d side wheel tickle coming in and going out and make a mentil note of it and just keep it in mind.
    But yes side wheeling as recommended a thing to avoid....so don't do that.


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