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Thread: Surface Plate

  1. #1
    Boolit Grand Master


    GregLaROCHE's Avatar
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    Surface Plate

    I just received a new granite surface plate, probably originally from China. It’s 40x25x8cm. Weighs around 23 kilos. I’ve been wondering what I need to know about taking care of it. I plan to keep it covered with part of the 1/8 in. plywood it was packed in. I know it has to be spotless clean when I use it, but should I put anything on it when not being used, like oil or wax? Also, I’ve seen that for large ones they should be leveled using three points. Do I need to devise some adjustable support for it, or because of it’s small size, will it be alright just sitting on a flat counter top? Is there anything else I should know?
    Thanks

  2. #2
    Boolit Grand Master

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    There are cleaners made just for granite plates. Windex works good but not sure if it will cut Prussian blue. Denatured alcohol is very good also. A soft cloth or paper towel and a light dampening of cleaner and rub,till dry. Make a cover with the ply wood and some short sides so it cant get pushed off sort of like cap. ours had a felt ot rubber lining for added protection.

    Pick up some fine flat ground stones. Always stone a part lightly to remove any burrs or sharp edges before putting on the plate. Before stoning the part rub the 2 stones together to clean and maintain surfaces. clean clean clean. any dirt or butts can scratch the plate and will throw measurements off. It can set on a solid bench maybe shim to level. No need for lubrication as it wont rust or need it, and the film will affect measurements again.

    As for accessories a decent height gauge, angle plate, vee blocks, light clamps cant twist tool makers or c. Will all be handy. Dedicate them to use on the plate to maintain.
    Height gauge, used to mount indicator for checking measurements and doing lay outs. Should have 3 point contacts on bottom.
    Angle plate, used for indicating to check square and holding parts during lay out.
    Vee blocks, holding round stock checking roundness
    Depending on how far you want to go a small sine bar
    If this is a no ledge plate the a post type base under it to leave the outside 2" so clamps can be used is handy

  3. #3
    Boolit Buddy
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    Good advise from Country Gent .

    My surface plate is sitting on a bench, I cut down a old towel to just cover it, and then made a 1/2" plywood box to slip over it to keep it covered when I am not using it.

    The height gauge is kept in the factory shipping box close by.

    So when I do go to use them, I use windex to spray the top of the plate and wipe with a paper towel, then use a dry paper towel to wipe down the base of the height gauge. Then both need to be CLEAN in order not to scratch the surface place when you are using them

    The same goes for making sure the part is free from burrs, and clean as well.

    J Wisner

  4. #4
    Boolit Buddy
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    Greetings,

    We used to use Bon Ami powder with water to clean the surface plates.

    You can buy a bottle of Starrett Surface Plate cleaner and it will last you a long time.

    Try to keep Aluminum and other soft metal objects off the plate. These soft metals get into the pores of the stone and act like a lap over time.

    Cheers,

    Dave

  5. #5
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    I watched a video with a guy in it that certified surface plates. He said he always used plain ammonia. My shop is pretty small. I think I would chase myself out if I used ammonia.

  6. #6
    Boolit Buddy alfadan's Avatar
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    As you're using it use your clean hands to constantly wipe it off. Towels or paper towels can leave lint which can throw things off.

  7. #7
    Boolit Grand Master

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    The granite plates are actually softer than the old cast iron plates and will scratch easier. But they are more stable not affected by heat, weight of the part (deflection)And the pores make spotting easier.

    I have a 18" x 24 cast iron plate thats also flame hardened. Due to its age its very stable now but also due to age and use it needs some touch up. 18 x 24 is a lot to hand scrape to bring it back in. Im thinking of a cheap 9 x 12 granite plate to use to lap it in to truly flat. One of the b grade plates would do fine and when done I will have 2 very good plates. I will need a second plate to hand scrape it and that will take days to do on that big of surface. ( from my last check there is one "hole" about 3" oval thats around .0012 deep and several spots .0007 deep). Not bad but a lot of surface to scrape down to the lowest points.

    The granite plates are very good and depending on accuracy level very flat. A or AA plate with gage blocks and pins becomes the shop standard. With a good environment, height gauge and indicator you can do amazing measurements.

    With the granite plates and heavier parts you need to be careful when loading it, uneven or a hard drop can chip them.

  8. #8
    Boolit Buddy

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    Absolutely NO ABRASIVES on a surface plate! Use a commercial surface plate cleaner such as the Starrett product or plain ammonia. Let dry thoroughly. It is rarely needed. I do a light cleaning on mine maybe once a year if that. And they are used weekly. Key is to only put clean degreased items on the plate.
    Quality surface plates will have three support pads located on the under side. There is a specification for it. I have a copy of the specs if you need. So you can apply a set of cork or felt pads if the plate did not come with it. Or if they get damaged from sliding the plate around. Very common on small surface plates or tool maker flats that get slid around a lot.
    I keep a soft cotton baby blanket (cheap at garage sales) on top of my surface plates. Then I have built 3/4 plywood covers that go over them. There is an air gap between the plywood cover and the blanket.
    Before using I always wipe the plates off with my hand. Amazing what your hands feel in the way of invisible particles of grit/dust.
    I also always wipe the bottoms of the height gage or other items off before gently placing on the plate. Check for burrs or rough edges on parts with hands. Lightly file or stone them away.
    Avoid sliding stuff around as much as possible. Especially aluminum items. And do not leave anything on the plate for extended periods. Yes, rust can form on the underside of a ferrous object left on a plate if there is sufficient moisture in the air.
    Avoid using the same place on the plate. Use all the plate surface to avoid wearing down one area. such as the side closest to you when on a bench.
    Wipe plate off again with hand and cover when done. A quality plate will retain its accuracy for many years when cared for properly.
    Last edited by gishooter; 11-21-2021 at 11:46 AM.

  9. #9
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    It definitely needs to be kept covered. But the thing to use on it is Lanolin and it is rubbed into the pores so they don't fill up with dirt, just like lubing cases the height gages and other things that you use need to have some lubrication between them and the plate or the plate acts like a Giant Arkansas Stone.

    This has been common practice for a hundred years?

    Also when cleaning your sharpening stones you use a "Figure 8 motion" as that is the motion that generates a flat surface. running two stones together is how you clean them of any metal transferring to the pores.

    I learned alot of this stuff fooling around with Telescopes, and also working at Gaiser Tool Company (now Coors-Tek) where we made really small stuff. I was around surface plates everyday, and it was a place where Millionths mattered.

    Randy
    "It's not how well you do what you know how to do,,,It's how well you do what you DON'T know how to do!"
    www.buchananprecisionmachine.com

  10. #10
    Boolit Master 15meter's Avatar
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    From my days building CMM's, I always preferred Rahn surface plate cleaner.

    Cleaned the plate nicely and put a nice bit of lanolin in the pores. Made moving gages or parts around the plate much easier.

    Never liked the Starrett plate cleaner or the other ammonia or solvent based cleaners, seemed to dry out the rock too much.

    I was told Rahn's was the same as D-L hand cleaner, I've used both and I couldn't tell the difference.

    Click image for larger version. 

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    Built these beasts in a prior life. Biggest one I installed sat on a 56,000 lb. surface plate. Rahn's made the plate shine. When you got done installing a 1/3-1/2 million dollar machine, you wanted it to look purty for the customer.
    Last edited by 15meter; 11-27-2021 at 09:50 AM.

  11. #11
    Boolit Buddy

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    I like the Rahn granite parallels. No other experience with their stuff. My AA granite angle plate is a Starrett pink. My surface plates are AA grade from Astral (just renewed certificate) and a small True Stone A or B plate. Don't remember as I have hardly used it.
    Never used the commercial plate cleaners myself. Just ammonia. I also used in in the metrology lab at the tech school. Climate controlled etc. Firm believer in cleanliness and caring for the gauges you put on the plates. If the bottoms and edges are cared for just like the plates then no issues moving them around. A nice shiny piece of granite is pretty!

  12. #12
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    I tried googling Rahn surface plate cleaner and didn’t find anything, except Rahn changed its name to Rahn Precision. When I searched for them, nothing came up. Anyone know where I can find information on Rahn Precision’s products ?

  13. #13
    Boolit Buddy

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    I believe they got bought out by Tru stone. Try this link:

    https://www.tru-stone.com/pages/smp.html

  14. #14
    Boolit Buddy

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    Astral got bought by Precision Gage co. Don, former owner of Astral, still operates the granite shop. Picture is of him on the website. He made my plate originally and also cleaned it up and re-certified it recently.

    They make very high quality granite gages. They are fairly close to me. Just a satisfied repeat customer.

    https://www.precisiongageco.com/product/astral-granite/

  15. #15
    Boolit Master 15meter's Avatar
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    Quote Originally Posted by GregLaROCHE View Post
    I tried googling Rahn surface plate cleaner and didn’t find anything, except Rahn changed its name to Rahn Precision. When I searched for them, nothing came up. Anyone know where I can find information on Rahn Precision’s products ?
    Check with your local Starrett distributor, they should be able to get it. May want to try some of the catalog houses, smaller distributors may shy away from ordering it because of the case minimum order.

    Or just try D-L hand cleaner, honestly I couldn't tell the difference between the two and D-L is stunningly cheaper than anything that has the Starrett label on it.

    I sold Starrett products for a number of years, always good stuff, just they were generally the most expensive kids on the block. Mahr was usually the only line I handled that was more expensive.

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