Surface Plate - The Velsey Company...New toy for my hobby shop.
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    Default Surface Plate - The Velsey Company...New toy for my hobby shop.

    Hey guys,
    I posted this in General but was told that it may get more response here.
    Picked this guy up today for a steal. It has some imperfections and needs to be lapped and I will build a proper stand for it in the coming days (suggestions on a propper stand would be appreciated). Anyone have any recommendations on where to get a lapping fixture for this size plate (24x36) or who have any experience with a resurfacing company in the Ohio valley, Kentucky, Tennessee area. I looked up Precision Granite in Tennessee and the have some decent testimonials. What am I looking at price wise to get this thing into A grade or even AA grade shape. Anyone have any data on the Velsey Company, I cant find anything about them on that standard search engines.

    It is going to be used in a hobby shop but I have an avenue to check/calibrate reference surfaces in the near future so that is why I am thinking about AA.

    s1.jpgs2.jpgs3.jpgs4.jpg Thanks

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    From what I understand, AA in an environment that isn't very well temperature controlled will be a waste. I remember reading somewhere that a 1° F temperature gradient from the top to the bottom of a 36" x 48" granite surface plate would dome it by something like .0003". I haven't heard of your brand of plate before but that engraved in "V" is pretty cool.

    Is the stand that's currently under it no good? It looks pretty stout. As long as the plate has support underneath at the same points that it originally did when it was calibrated it should be good to go. Most plates I've seen have either got permanently attached feet at those points or markings that indicate where they should be.

    One thing I would definitely recommend after you get it resurfaced is to get a fitted cover and also to clean the plate before every use.

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    I'd say that size of plate is on the border of what I'd put in the back of a truck and take to a metrology shop to be lap'd and certified. You can bring small plates to them, but typically they will prefer to come to you to do bigger plates. If you wanted it grade AA but can't vouch for your environment, I'd take it to the lab. Doing so, you'll know it's Grade AA, but only in the best of circumstances. For 99% of shops, a certified "shop" grade B plate is plenty accurate and "inspection" grade A is even better, but most don't really need "Lab" Grade AA or higher. The higher grades will still be usable as they wear down however.

    Most lapping services will charge more for the grade you're after and less for the size (to a point), because lapping a 24x36 or 72x36 area takes a similar amount of time, but taking a bunch of passes to get it spec'd to Grade AA takes much longer than a couple passes to touch it up or bring it to Grade B.

    Remember Grade A is twice as accurate as Grade B, and Grade AA is twice as accurate as Grade A, so the specifications and requirements to certify multiply as you go up. A surface plate is one of the master standards in a shop that everything gets compared to, it's not something you want to fudge. It doesn't have to be the highest standard, you just want to know what standard it is.

    As far as the stand goes, if the plate sits on 3 points at a functional height for your work, and it doesn't want to tip over if you lean on the wrong spot, it's fine.

    I'm not sure about your area, but we had a local shop quote a 48x72 plate at a friends shop awhile back that was Grade B on 3/4 of the surface and non-passing on the rest. To get it to Grade A was going to run just over $1000. With how it was used (not very often), we decided to work with it and marked off the worn non-passing area.

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    Thanks for the reply! I am well versed in thermal expansion of materials (Engineer is my day job). The stand has 3 - 1"x 2" x 1/8" HSS slats that are weld seam and were not machined prior or after they were attached to the stand so they have a bow in them and are uneven and allow the plate to wiggle. I can see light through the mating surfaces.

    My wife is making me a fitted leather cover for it and I am in the process of building a bigger shop (currently in 2 car garage and going to a 50 x 100 that will have HVAC at our new property).

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    Quote Originally Posted by M.B. Naegle View Post
    I'd say that size of plate is on the border of what I'd put in the back of a truck and take to a metrology shop to be lap'd and certified.
    That is what I was thinking. I will bring the new stand with it and get it lap'd and calibrated on it in the same bearing conditions that will be in my new shop. I will likely only need .0001" accuracy on it for calibration of soils laboratory equipment. Is this doable with "A" grade?

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    Quote Originally Posted by jmoore2784 View Post
    That is what I was thinking. I will bring the new stand with it and get it lap'd and calibrated on it in the same bearing conditions that will be in my new shop. I will likely only need .0001" accuracy on it for calibration of soils laboratory equipment. Is this doable with "A" grade?
    Not intending to shill for Starrett, but the link here has links to the standards for surface plates. You can also find the Federal Standard separately if you want.

    Precision Granite FAQs

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    Quote Originally Posted by specfab View Post
    Not intending to shill for Starrett, but the link here has links to the standards for surface plates. You can also find the Federal Standard separately if you want.

    Precision Granite FAQs
    As long as a post is informative and answers or helps answer a question I've no objection to a specific company being mentioned.

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    Quote Originally Posted by jmoore2784 View Post
    That is what I was thinking. I will bring the new stand with it and get it lap'd and calibrated on it in the same bearing conditions that will be in my new shop. I will likely only need .0001" accuracy on it for calibration of soils laboratory equipment. Is this doable with "A" grade?
    "A" grade for a 24"×36" plate is about .00015" overall. "AA" would be ~.000075" and "B" grade would be ~.00030".

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    i was debating the same a few years ago, but now im glad i have an aa plate. the difference in cost is marginal when spread over the years and there are so many inaccuracies when trying to measure to 0.0001" that its nice to have something to rely on.

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    Quote Originally Posted by jmoore2784 View Post
    That is what I was thinking. I will bring the new stand with it and get it lap'd and calibrated on it in the same bearing conditions that will be in my new shop. I will likely only need .0001" accuracy on it for calibration of soils laboratory equipment. Is this doable with "A" grade?
    Size is amenable to toting it to the refinishers, but still. A(ny) Grade "A" (or anything better) is easier to hit and reliably hold to spec if the plate has been in-place, on its stand, and for a month, preferably several, before it is seen-to.

    EG: The refinisher/calibrator tech makes a site visit with his gear, his time and travel vs the plate's time and travel.

    Granite DOES flex. Just not a lot.

    The figures for "A" or "AA" are down where a fraction the wavelength of visible light happens to be "a lot".

    JMNSHO, but AFAICS, a "B" plate that really IS no less than "B" should be good enough, and an "A" certainly would be.

    I can't see the "clean room" facility expense and nuisance of Micron air filtration atop stabilized temps needed to make best use of a "AA".

    Unless, of course, your lab already HAS those things?

    Separate item, but..

    "Same bearing conditions" is optimistic if not also fictional. They won't be.

    I don't see an "AA" certified then MOVED to some other point on the planet as a likelihood, but ask the refurb/calibration firm about that.

    Here is one that lists your area as within their service coverage:

    calibration and resurfacing service of granite surface plates - Cleveland OH, Chicago IL Optimal Calibration

    They have competition.

    My "Herman" Grade "A" looks to be of the same somewhat less-common brownish granite as your Velsey. Black is stiffer, can be made thinner. Grey and pink are also more common. Each colour has its own good points,

    Herman usually gets the credit for the first such use, but only if you have not had the privilege of touring the Great Pyramid of Cheops from the inside, and the adjacent temple of the Sphinx!



    Here is an article that references - see right-hand side-bar - the resurgence of granite "in our time", at the hands of Herman, Velsey, and Rahn and the development of the instruments to measure and correct error in the plates:

    how to selectgranite surface plate - Knowledge - Jinan Fortune Precision Machinery Co.,Ltd
    Last edited by thermite; 03-28-2020 at 01:50 AM.

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  17. #11
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    Barta's should be able to lap that in at your shop for a good price.
    I'm not sure how far they travel but I've used them for years. They do good work.
    I'm near Akron Ohio.

    Bartas Home


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