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Which Quality For Surface Plate?

Discussion in 'METROLOGY - MEASURE, SETUP & FIT' started by ybyo, Jun 29, 2016.

  1. ybyo

    ybyo Turkey Swarf Registered Member

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    Dear all,
    First thing first i'm very new to forum so i would like to salute you from Turkey. My name is Yavuz and have mechanical engineering degree. I'm also hobby machinist, don't have a dedicated garage. Just working on my spare times in a dedicated room inside my flat.

    Nowadays i am looking for a granite plate in size of max 400x400 mm (~12 in) and reasonable weight to handle it. Just looked for suppliers and learnt about their different standarts, quality etc..
    One of them returned me that they have A and B grades in din 876 standart, also, for both south african and chinese stones. I think that A and B reffers to 0 and 1 grades in standart. (attached image)

    I would like to have your opinion, in my case which of them should i choose? I'm not so pro right now and my machines / tools are not in space engineering grade :) Actually i would like to have that plate for some bed way scraping. With a bit of limited budget i'd like have the most suitable one.

    Can you help me on that issue, would grade B (1) and chinese stone be so bad?

    thanks
     

    Attached Files:

  2. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    Yavuz, welcome the forum. I think you will find this a friendly and helpful forum.

    I am not so sure that your attached flatness chart corresponds at all to the grades A and B for surface plates, but I am in the US, and we have our own standards. Here in the US we also have grade AA, along with A and B. The tolerances are different for different sizes of plates, and also include repeatablility limits.

    http://standridgegranite.com/products/surface-plates
    http://standridgegranite.com/images/stories/docs/forms/fed spec ggg-p-463c.pdf

    What you need in a surface plate depends on what you are going to measure, to what tolerances, and to what repeatability. Grade B is commonly used for in-shop surface plates. If you plan to scrape things into higher tolerances, or do high precision grinding or layout work, you may want to go to a higher grade. Grade AA only really makes sense in climate controlled metrology labs. All that said, inaccuracies are to some extent cumulative, so a higher tolerance surface plate helps to build confidence in your home workshop measuring capabilities.

    In my opinion, everyone making accurate parts needs measuring tools including flat (surface plate), length (gage blocks), and angles [sine bar/table, known accurate square (certified granite angle block and/or cylinder square.)]

    You should be able to prove your tools and machines to your needed accuracy...
     
    4gsr, ybyo, Uglydog and 1 other person like this.
  3. Charles Spencer

    Charles Spencer Active User H-M Supporter-Premium

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    Firstly, please accept our condolences for the attack on your airport.

    Second, from your chart I see that the DIN876II is listed as accurate to within 1.06 mils (0.00106) in your chart. That's almost twice as accurate as the lower grade one.

    In my experience, when I'm not exactly sure what to buy, I have a simple rule: Never buy the cheapest or the most expensive. I use this for all types of purchases.

    I think I'd go with the one I mentioned above unless the price is really the most important factor.
     
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  4. Ulma Doctor

    Ulma Doctor Infinitely Curious H-M Supporter-Premium

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    Hello Yavuz,
    welcome to the forum!
    i try this rule when buying, buy the best you can afford.
    you can upgrade later, if necessary, as your needs demand.
    sometimes you can sell the old items you no longer use to fund the purchase of something you will use.
    all the best
    mike:)
     
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  5. Uglydog

    Uglydog United States Active User H-M Supporter-Premium

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    Yep, consider your projected needs and your current budget.
    Get the best you can afford.
    But, also consider the sequence in which you need/want to purchase machines/tooling/inspection/etc equipment.
    Obviously, if the deal of the year comes along. then you may need to scramble.
    But, keeping priorities in line is critical.

    Also, (and don't tell my wife I wrote this) don't forget the kids need winter boots and breakfast.

    Daryl
    MN
     
  6. T Bredehoft

    T Bredehoft Active User H-M Supporter-Premium

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    At the level of precision I work, the cast iron top of my table saw is flat enough, I don't have, don't expect to have a surface plate.
     
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  7. Uglydog

    Uglydog United States Active User H-M Supporter-Premium

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    I've heard of others substituting plate glass.
    All depends on tolerances and application.

    Daryl
    MN
     
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  8. ybyo

    ybyo Turkey Swarf Registered Member

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    Thank you for your kind feelings, also same here about Orlando, Paris, Brussels, Ankara also.. A wicked universal thing.

    I think i will go with sum of your suggestions, top quality until to affordable budget (i dont need winter boots ;) ). But i think for hobby purposes 12x12 in^2 is more than enough.
    In the first time i will use it to take referances while reconditioning my lathe bed ways and gibs mostly. You see there are visible cutting left overs on gib surface, of course that's a cheap mini lathe i own (7x12).
    While making projects (double acting steam engine / bollaero diesel) i clearly understood required tolerances and finishing detail.

    Thanks again for your help, i'd like to join other issues and threads later.
     
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  9. Wreck™Wreck

    Wreck™Wreck United States Active User H-M Supporter-Premium

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    You are a hobbyist no? If so buy the lab grade surface otherwise you will always have fears about accuracy.
     
  10. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    If you are reconditioning tools and machines I recommend a grade A surface plate. The work on your machines will not be more accurate than your surface plate. Depending on price, you might choose an AA plate for peace of mind and a longer service life before it exceeds grade A standards.

    In my first post I was also going to give you my condolences over the violence you have been experiencing in Turkey. I did not, staying on topic, but I definitely do care about the safety of you and yours and indeed everyone on this planet.
     
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  11. EmilioG

    EmilioG United States Active User H-M Supporter-Premium

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    I was looking at PrecisionGranite surface plates and they have some good new choices for smaller plates under $300.00
    I may go with one of these instead of buying a used plate of unknown accuracy. Black granite, 12 x 18 Grade A or B.
    Carts with caster wheels are $415.00
     
  12. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    Precision Granite and Standridge Granite are sister companies. Their products are top notch. They are both made in the same plant. Here is a tour:
     
  13. FanMan

    FanMan Active User Active Member

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    I use a 12" square piece of precision ground tool steel stock, which I cold blued with gun bluing for some corrosion protection and put rubber feet on. Accurate enough for what I need to do, small and light enough to store in a drawer of my rollaround, and mag base indicators stick to it.
     
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  14. Pmma-Granville

    Pmma-Granville United Kingdom Steel Registered Member

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    Hello!
    Off topic but I like your avatar!
    Great machine the tiger 1!
     
  15. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    My first surface plate was a piece of 1-1/4 thick A-36 plate, 9 x 11, dad surface ground it on both sides and flipped it a couple of times called it good. Still have that piece of plate. Use it for ballast material in the bottom of one of my roll away cabinets.
     
  16. Wreck™Wreck

    Wreck™Wreck United States Active User H-M Supporter-Premium

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    A size and accuracy that are required by your particular work, no more no less.

    Took this at work today, 18" (450 MM) X 48" (1220 MM) X 96" (2440 MM), 6300+ Lb., .001" across according to the label.

    i-mWR2FT3.jpg
     

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