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  1. #1
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    Default is this a surface plate

    I came across this online, and it looks a heck of a lot like a surface plate. The specs are 4-foot x 3-foot x 4 inches. The seller doesn't know if its a surface plate or not. just from visual inspection of the picture and the stand it's in makes it look like one. If anyone can point out something or if I go and look at it in person what I can do to get a rough idea of precision. If I look at it I plan on bringing some Parrales and a feeler gauge or something and use that. Thanks for looking.67476055_1302401003249422_3445789469158932480_n.jpg

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    It looks like a surface plate, but it's thin for the L/W. That means that even if properly supported (which that frame may not be doing), it's going to have lower load capacity before deflecting out of spec (whatever that may be).

    If your needs aren't critical and the price is right, check it out. At worst, a thin plate is easier to move. Weight will be around 670lbs for the plate alone, if the size given is correct.

    If you have a precision level that's probably the easiest way to check it. If you don't then you may want to get one.

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    its $250... and about a 50-minute drive from my house. Im just a beginner with a craptacular Bridgeport and even worse lathe, I would love to be able to improve or just scrape some stuff for fun.

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    It looks like it was a surface plate but with those gouges in it now, it is a nice granite step.

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    Large stone slabs, which obviously need sturdy supports, are used in making candy and in the "Cold Stone Creamery" ice cream shops. The candy slabs are often made of marble, which is too soft for use as a surface plate. I think the Cold Stone shops have refrigerated slabs.

    I think surface plates will have only three contact points on the bottom, with a means of leveling the top of the plate. Of course, there are different grades of precision in stone slabs used for layout and precise measuring.

    Larry

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    I did a little looking on google and the Coldstone refrigerated tables look to be around 1-2 inches thick. that doesn't really mean much seeing as they could have used a thicker slab. I'm still unsure, I'm planning on looking at it tomorrow so I should know more.

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    The aspect ratio between that surface plate and the snow blower in the background suggest that plate is 2' x 3' at the largest. The 4" thickness would be acceptable for 2' x 3'. The top looks trashed. Save your money and keep looking, that one is over priced even if it was pristine.

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    the seller measured it to be 4' by 3' by 4"... I can't tell from the pics if those are gouges or some crap on the top of it. the person seems open to offers as well so I wouldn't be ashamed to offer half asking. it has been up for a while now

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    I believe the thinnest it could be for B grade is 6-8 in thick. The surface looks trashed and, to assess if it is somehow near to flat you need at least a trustworthy parallel, and tenth indicator mounted on a (preferably non-magnetic) stand.

    You run the stand on the parallel sitting on the plate, indicating the plate and you map the surface of the plate.

    Better setup would be two 123 blocks, parallel sitting on blocks more or less at Airy/Bezel points (not enough difference to argue in this case) running the base of the indicator on the plate, indicating either the bottom or the top of the parallel.

    If you can observe anything with a feeler gauge, it's tombstone or kitchen countertop grade.

    I second the suggestion not to waste your time and money.

    A B-grade 3x4 plate weighs approximately 3/4 ton.

    Paolo

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    I've seen pics that look like gold, turn out to be junk. I've also seen pics that look like junk, turn out to be gold. Most stuff that looks like junk, is junk. Most stuff that looks like gold, is junk. Long story short, never judge by pics. Welcome to the wonderful world of used equipment purchasing, lay eyes on it, before laying cash down.

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    Welp... depends on what you want it for? It does look like the top is trashed, however, for $250, it might be better than what you have (nothing?)?...

    Surface plates are expensive, and expensive to ship because they weigh so much.... Go look, bring an indicator and see if it fits your purpose....

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    A surface plate can have scrapes and still be OK but you don't/won't know with not having it calibrated.
    You can buy a small brand new A block for around 100 bucks.
    WoodRiver - Granite Surface Plate 12" x 18" x 3" A Grade

    An A block can go to about 24 X 36" and still be within one ten thousandths inch.

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    if it will suite your needs, $50 tops.

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    It does look like it's been used AND abused. I would consider this an "SPSO" (Surface Plate Shaped Object). I might be better than what the OP is using now, but not much.

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    In answer to the OP

    "Not any more"

    You can buy a smaller crap Chinese one for 100 bucks, why drive somewhere to buy some crap Chinese one that has been used as a parking spot for tractors

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    I still wonder what happened to the one I saw at auction 25 years ago, went for like 1000 bucks

    IIRC, 8x12 feet, about 18 inches thick.

    what, about 12 tons.......

  22. #17
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    Quote Originally Posted by Paolo_MD View Post
    If you can observe anything with a feeler gauge, it's tombstone or kitchen countertop grade.

    Paolo
    Or it could be repurposed as a stepping stone in the garden.

    NY state is not a desert for machine tools. Stones in NJ come up at shop auctions on a regular basis, often getting no bids. Be just a little patient.

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  24. #18
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    I would absolutely buy a legitimate stone but everything is more than 2-3 hours away. This was the largest and closest. Im looking to get a tool room grade... Something like a shars 18x24, does anyone have recommendations for cheap and good enough stones?

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    NYS where? Buffalo? Albany? Woodstock? Start watching bidspotter for auctions in your area. There are still places that recondition and grade/certify surface plates, not outrageously priced if you are willing to bring the stone to them and it's not a basket case.


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