why did my surface grinder do this?
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  1. #1
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    Default why did my surface grinder do this?

    I've started scraping in my shop as a prelim to Rich King's class in Olympia in August. I still have the chunk of cast iron I got from a previous class to make 1-2-3 blocks out of. I scraped the better side in OK. The worse side was pretty bad. So I thought what the hell I'll surface grind it and start with that.

    The surface grinding went OK (I thought). But when I put the ground side on the blued-up surface plate, only the very tips of the ends were blue. I would have thought it would be better than that!

    metalmagpie

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    Well, grinder not in good shape, surface plate not flat or you ground a very heavy pass and heated the heck out of it. Need more info and you'll probably have to do some test grinds. I'm assuming the other side was flat and mated well to the SG chuck with no rocking or weirdness.

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    Wheel right?

    Ancient Norton book says 37C 30 grit K grade - that there is a silicon carbide wheel

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    Quote Originally Posted by metalmagpie View Post
    The surface grinding went OK (I thought). But when I put the ground side on the blued-up surface plate, only the very tips of the ends were blue. I would have thought it would be better than that!

    metalmagpie
    If it actually MATTERS (not always...) it can be "better than that".

    How about you simply "book end" that item - shoulder block of "don't care" each side - same-height, same width, same alloy - and assure over-run past your "sandwiched" block, both directions.. all sides, if you NEED to get fussy..

    ... so the entry and exit edges and corners of your "chosen one" are no longer the points where the wheel takes up and releases the pressure vs slack balance, ... nor the worser effects (ALWAYs present, if only just barely..) of direction reversal?

    Grinding thing. "Needful" category. I did say "not always?"

    Not a lot to do with scraping. Not YET, anyway.

    Bluing is just the "snitch" that ratted you out as NOT having done dotted ALL the "i"'s, nor crossed ALL the "t"'s!


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    I'm thinking it must have been heat. I don't have my flood coolant working yet.

    My thinking goes like this: anywhere except on the ends, the heat being put into the part by the wheel makes the metal expand straight up (since the metal on either side can't move). Expanding up, more of it gets ground off. At the ends, the metal can expand sideways plus it has free air next to it so it won't get as hot.

    I'm hoping this problem will go away when I get my coolant working.

    metalmagpie

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    It's called sucking it up.
    Bob

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    Quote Originally Posted by metalmagpie View Post
    I'm thinking it must have been heat. I don't have my flood coolant working yet.

    My thinking goes like this: anywhere except on the ends, the heat being put into the part by the wheel makes the metal expand straight up (since the metal on either side can't move). Expanding up, more of it gets ground off. At the ends, the metal can expand sideways plus it has free air next to it so it won't get as hot.

    I'm hoping this problem will go away when I get my coolant working.

    metalmagpie
    Re-inventing the wheel is OK. If yah but LEARN new stuff, from the doin' of that.

    Coolant is good. It can make accomplishing better work easier.

    But it won't make the geometry nor wear of the grinder it is on any more perfect.

    Helps if you are ALSO the only guy on Planet-Earth with a surface-grinder so PERFECT as to be as rigid and free of unwanted play or movement as the core material of a Neutron star? But ARE you, really?

    "Must be nice" to not even have to worry about "spark out", but I had to take the ole B&S, Taft-Pierce, and Parker-Majestic goods just as they were "real world", back in the day.

    But there you have it.

    Shit MOVES, Pilgrim.

    Some of it just moves more - or less - than OTHER shit.

    Spark-out is not the same as "perfectly flat and linear".

    It just means the almost-straight curve has finally gone STABLE to whatever range of goodness it owns ... or does NOT ... be that good, bad, or indifferent.

    You'd have to know surface grinders? Used ones? With wear, even?

    Bob said "suck it up?" I might say "lap it out!"

    The grownups claim it tastes much the same.

    Either way, you have more work to do!


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    You don't say how much? .00002" or could it be .001" How can someone help you if you make us guess? Just to have a conversation? I have better things to do then guess at whats the issue. I got a letter from someone who attended the other class you mentioned...from one of the students...he was not to happy with the results......

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    Quote Originally Posted by thermite View Post
    ....
    Bob said "suck it up?" I might say "lap it out!"
    Suck it up as in live with it and the grinder sucking it up two very different things.
    SOP in precision flat grinding and a normal problem. It is not only the part is is commonly or often more wheel growth.
    Makes it look like the part has "sucked up" in the center during the grind leaving the part "hollow" or thin in the middle.
    Bob

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    Quote Originally Posted by CarbideBob View Post
    Suck it up as in live with it and the grinder sucking it up two very different things.
    SOP in precision flat grinding and a normal problem. It is not only the part is is commonly or often more wheel growth.
    Makes it look like the part has "sucked up" in the middle during the grind leaving the part "hollow" or thin in the middle.
    Bob
    OP is chasing guesses about "edge cases" - as if "read it on the internet ..somewhere" - and more or less at random without any indication "so far" that he has even gotten the "most basic" parts of a grinder's tall pyramid of a "food chain" assessed and made right - or at least taken on board, if not yet in his ken to compensate for.

    "Preaching to the BANDMASTER, not just the Choir" I am sure, but there's both a "learning curve", and a "maintenance minimum" to being able to get best results in a reasonable time and cost with minimal risk or scrap loss. Not an "instant gratification" exercise.

    AFAIK, you have both. OP has neither. Yet.

    I DID HAVE the first. Rebuild included.

    But so VERY long ago I won't kid myself nor waste time nor money owning a surface grinder. Not even if brand-new and as a free gift and rigged-in at no charge.

    I can't "keep up" with the "get your HEAD in the proper cockpit" TIME consumption load .. nor even the investment in good wheels, plus-plus-plus.

    Sumthin' needs ground?

    It goes OUT!

    ... to someone who does it all day, every day, all year and DOES have the up-to-the minute "best current practice" orientation and collection of wheels, fixtures, dressers ... and more than one type of grinder.

    A "professional grind shop" in other words.

    Lot's of machine-tools make "fun toys".

    Grinders? Unless tasked so as to coin money to pay the bills?

    They are mostly just TEDIOUS sucker-uppers OF time and money.

    There's good reason so many used GS's are out there, and so many "revenue" shops no longer make space for one under their own roof.

    As I'm in surplus of time and money-wasters arredy?

    "Send it out" stands!



    The OP MAY have sound reason to go another route. Worthwhile payoff may come good in his future.

    But that "learning curve"- potential need to rebuild - and the INVESTMENT do not come with easy nor cheap bypasses.

    2 Cents . and no surface grinder's worth! "Cheat" that I am in me dotage?

    I "just buy" 1.2.3 blocks. And not-only! Cheaper that way.

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    OTOH, if you approach it right, surface grinding is the easiest job in the shop. BTW, it's easier to grind hard steel than soft. Was the 1-2-3 block hard or soft? Wait, you scraped it, so probably soft. Use no finer than a 46 wheel, on the hard end, coarse open dress so you don't make heat, and spark it out. Should work fine with or without coolant.

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    Quote Originally Posted by Richard King View Post

    I got a letter from someone who attended the other class you mentioned...from one of the students...he was not to happy with the results......
    Not happy with results? In comparison to Metalmagpie's problem, maybe this guy was HIGH in the middle. heh, heh, heh

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    Quote Originally Posted by Conrad Hoffman View Post
    OTOH, if you approach it right, surface grinding is the easiest job in the shop. BTW, it's easier to grind hard steel than soft. Was the 1-2-3 block hard or soft? Wait, you scraped it, so probably soft. Use no finer than a 46 wheel, on the hard end, coarse open dress so you don't make heat, and spark it out. Should work fine with or without coolant.
    Surely. And I bought five pair, new and "decent" for $60. Six bucks don't cover a lot of my time.

    Seems to me if one is going to "make stuff to learn stuff" - a righteous enough exercise - yah'd want to make that "stuff' sumthin' yah canot readily purchase so cheaply?

    Or even "at all"?

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    has anybody out there (lightly) blued up a ground part and it was perfect? thats why you scrape/lapp.

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    I haven't blued one up, but have laid an optical flat on them. Generally no trouble with flatness on a lump, but I can fight the thinner pieces just like everybody else. My B-S grinder isn't in what anybody would call great shape, but it does better than its condition would have you suspect.

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    Quote Originally Posted by dian View Post
    has anybody out there (lightly) blued up a ground part and it was perfect? thats why you scrape/lapp.
    Definition of perfect?

    I have a pair of 3/4 x 1 1/2 x 12 parallels (shop made) that check flat and parallel with a tenth indicator to less than .0002". No lapping, just very very careful (and tedious) surface grinding....

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    Quote Originally Posted by dian View Post
    has anybody out there (lightly) blued up a ground part and it was perfect? thats why you scrape/lapp.

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    Agree not enough information to make comment.
    wheel /coolant / machine / neghbor's dog / feed rate / lose chuck / wrong brand of beer /zombies / nice looking girl walking past /poor lighting / standing on a nail / got to pee / thinking about the next job / forgot that this is a mill /

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    Quote Originally Posted by michiganbuck;3558069[B
    ]Agree not enough information to make comment.[/B]
    wheel /coolant / machine / neghbor's dog / feed rate / lose chuck / wrong brand of beer /zombies / nice looking girl walking past,
    Just to


    I am reasonably sure the part heated up and "sucked up" into the wheel, which is why it is only contacting on the ends.

    Now the cause of the heating is pure speculation. Loaded wheel, too fine grit, excessive doc,etc...

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    Wheel too fine, too hard, too much stock, wrong kind of wheel, wheel loaded and not dressed, fail to go off part at ends to add some cooling time, cross too much or too fast, fail to use some coolant, poor dress with not at a facet.

    One thing I have seen often in shops and now on youtube is show-off grinding with little off-the-part at ends on long travel of 1/16 or so, and less... the least amount possible for zero cooling time… and crosses so quick there is no time for any cooling there.

    No I don’t know if this was a factor.

    Heat cause so much swelling that for fussy parts we would let them set an a cast iron plate for a half hour then only touch with wearing cotton gloves for inspecting.
    Last edited by michiganbuck; 05-30-2020 at 06:36 AM.

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