Video of measuring a surface plate
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  1. #1
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    Default Video of measuring a surface plate

    In a recent video I posted from Japan of surface plates being scraped the subject of measuring them has come up. This video is reasonably good and shows how most people will check one today. It aint exciting but if you are interested it isnt that bad.

    Gauging Quality, Episode 1 - Surface Plates - YouTube

    I will also post a link to this in the metrology forum.

    Charles

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    i believe they have something wrong there: thicknes of paper is 400/1 000 000"? (0.01 mm). the paper i write on is ten times thicker. if half of that was the tolerance of the plate, it would be complete junk.

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    Default onion skin

    Quote Originally Posted by dian View Post
    i believe they have something wrong there: thicknes of paper is 400/1 000 000"? (0.01 mm). the paper i write on is ten times thicker. if half of that was the tolerance of the plate, it would be complete junk.
    .
    onion skin paper comes in different thicknesses. 9lb is about 1/2 thickness of normal paper which is normally 0.1mm to 0.075mm so it would be 0.05mm to 0.038mm
    .
    the thinner onion skin 0.01mm is hard to find. it is used as a feeler gage and as a shim. sometimes it is sold in rolls rather than sheets at tool supply stores. some times it is metal and not paper 0.01 mm stainless is more like a foil
    .
    it is still called onion skin even if metal, plastic, paper, etc
    .
    mylar plastic can be bought thin too. Saran wrap the plastic used to cover food is a good example

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    Quote Originally Posted by dian View Post
    i believe they have something wrong there: thicknes of paper is 400/1 000 000"? (0.01 mm). the paper i write on is ten times thicker. if half of that was the tolerance of the plate, it would be complete junk.

    They were showing how the plate is measured, the guy doing it is the head of a company that sells tools and offers calibrations services. How many years do you think it has been since he actually had his hands on the equipment? I wouldnt be surprised if there wasnt a bit of error in some of the information.

    Charles

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    Here's another video showing some lapping methods.




    That paper thickness mistake.. he showed it reading 200 arc seconds, which works out to about 4 thou, 4000 micro inches, not 400.. but the rest of the video was excellent.

    Ray

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    0.01 mm onion skin was and is used to check 2 surfaces. if you put 10 evenly spaced pieces between 2 objects and some pull out by hand but not others it is because of varying space between the 2 objects.
    .
    it is not easy to find but 20 micron rolling paper for cigarettes is about 0.02 mm. if you used multiple evenly spaced strips they could be any thickness, the point being none come out easy but all under contact compression between 2 objects. very common to use to check bowed or warped sutfaces

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