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Grit Comparison Chart

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  • 10/14/2015 at 6:04 am #29196
    Ravenbrook
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    • Topics: 8
    • Replies: 11

    My brother in Law is the lead painter at a BMW dealership and he said he can get me up to 5000 grit sandpaper. He recently gave me some 1500 grit which I’m going to cut up and mount to some paddles like the 100/200 after I’m done with them. My question is looking at the WE Grit Comparison Chart where would 1500 grit sandpaper fall? Right at 1500 grit? Or higher up the chart. I’ve heard someone say that not all grit is the same so even though two different media are both 1500 grit they can have totally different results. Also, what would the 5000 grit
    be equivalent to?

    Thanks,

    Rick

    10/14/2015 at 9:34 am #29197
    CliffCurry
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    • Topics: 42
    • Replies: 461

    Aloha Ravenbrook,

    Mr. Wizard and a fellow named Komitadjie both have made serious attempts and put ALOT of effort to make similar versions of a Comprehensive Grit Comparison Chart.

    Wizards is here: http://myplace.frontier.com/~mr.wizard/GLGC/GLGC.png
    Komitadjie’s is here: https://docs.google.com/spreadsheets/d/1VaTf3MXuwuvH-QLwOci4f9B9Zhkbuu1wjoSCZIUsR-o/edit#gid=0

    I havent double checked that the values line up for every single thing between charts but Id guess the results are very similar for what we are interested in. Mr. Wizard at one point even mentioned Komitadjie as his inspiration in doing his own independent version. Thanks to both of them!!! 😉

    I also use sandpaper strips in the higher end area with great results. The confusing part is there are at least 3 or 4 grit “standards”.
    Here is a quick read to see the differences: http://sizes.com/tools/sandpaper.htm

    Hopefully Mr. Wizard can correct me if I am getting this wrong but most sandpaper here(U.S.A) is in the CAMI(Coated Abrasive Manufacturers Institute) scale. I have found the very fine grit wet/dry auto paper usually has a designation of “P” in front of the number, p2000, p2500, p3000, etc. There is a BIG micron difference between these types.

    If you look on either chart you can see the WEPS 1000 grit stone is at 7u(microns). Compare that to p2500 grit paper at 8.4u. What you will hopefully find in following the 1000 grit WEPS with the p2500 is that the p2500 can leave a much smoother uniform finish(almost mirror smooth in appearance) I follow that with p3000 which is technically the same micron rating as the original WEPS 1000 grit stone, but there is a WORLD of difference in how it looks.

    After that you are nearly at the finish line. You can choose micron abrasive films or paste/strops to finish off to a sweet mirror finish. If I had p5000 (5u rating), Id use it in a heartbeat and go straight to strops! B)

    Another neat trick is to take the last grit of paper and go directly sideways along the edge bevel, leaving a perfect satin finish with no scratch lines, even tho you dont take it to mirror finish. I then come back and sometimes put a micro-bevel with the same paper on top. Good fun!!! Hope that helps…

    2 users thanked author for this post.
    dulledge, Ravenbrook
    10/14/2015 at 11:06 am #29199
    tcmeyer
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    • Topics: 38
    • Replies: 2098

    As Cliff says, there are several different grit cross-references. Mr Wizard, a frequent denizen of these halls of knowledge, will freely share them with you. For instance, there is a difference between 1500 grit and P1500 grit paper.

    I, however am old,and therefor old school, which holds that the grit rating is the number of particle diameters which will fit into a span of one inch. For instance, 15 micron abrasive would be 1,693 grit, as there are 1,693 fifteen-micron particles that fit into one inch. One inch is 25.4 millimeters, or 25,400 microns. Twenty-five thousand four hundred divided by 15 is 1,693. It works for me.

    That having been said, there are almost no vendors out there who hold to my standard. Everybody seems to have their own numbers.

    FWIW, if I wanted to mount abrasive paper or film to something for use on my WEPS, I’d consider removing the old 100/200 plates and replacing them with 1/8″ thick X 3/4″ wide aluminum or brass, using double-faced adhesive tape. Then lap the faces on a plate of glass or granite, working my way up to something like the 1500 grit paper.

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