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Thread: granite vs. float glass?

  1. #1

    granite vs. float glass?

    I have several older (not antique) planes that I should flatten the bottom (soles?).

    How do 1.5"-2" thick granite cut-offs compared to float glass for this purpose?

  2. #2
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    depends on how flat the granite is. If it's flat and nice and long then go with it. Float glass can be shimmed a little. Float glass on top of a granite cut off with some sheets of paper under to shim things to flat makes for a nice cheap and useful flattening substrate. For smaller planes, blades etc, (anything that finger pressure can easily lap a bow, convexity into you can shim the glass so it is convex just a touch. Helps with those small items.

  3. #3
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    Quote Originally Posted by Dave Lewis View Post
    I have several older (not antique) planes that I should flatten the bottom (soles?).

    How do 1.5"-2" thick granite cut-offs compared to float glass for this purpose?
    Do you have some way of determining how out of flat the bottoms of your planes may be?

    If a plane isn't displaying a problem associated with the sole being out of flat, it is likely not in need of a sole flattening.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  4. #4
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    Float glass can flex if it's used on a surface that's not flat. I use the top of my table saw and sandpaper for this purpose.
    Sharp solves all manner of problems.

  5. #5
    Quote Originally Posted by Jim Koepke View Post
    Do you have some way of determining how out of flat the bottoms of your planes may be?

    If a plane isn't displaying a problem associated with the sole being out of flat, it is likely not in need of a sole flattening.

    jtk
    As we would say back when the world was mostly sane or at least I was young: Right on brother.

    ken

  6. #6
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    I use a 36" threshold from Home Depot for my planes. I don't use it to flatten them but to sand and shine them up

  7. #7
    Quote Originally Posted by Ralph Boumenot View Post
    I use a 36" threshold from Home Depot for my planes. I don't use it to flatten them but to sand and shine them up
    As sure as the Sun rises in the East Ralph's planes are shiney. He knows of what he speaks. BTW, if you would like to see some great plane restorations check out Ralph's blog https://accidentalwoodworker.blogspot.com

    ken
    Last edited by ken hatch; 01-01-2019 at 7:39 AM.

  8. #8
    Quote Originally Posted by ken hatch View Post
    As sure as the Sun rises in the East Ralph's planes are shiney. He knows of what he speaks. BTW, if you would like to see some great plane restorations check out Ralph's blog https://accidentalwoodworker.blogspot.com

    ken
    Man, they sure ARE! Nice work Ralph! (Hope your cold improves.)
    "All that is necessary for the triumph of evil is that good men do nothing."

    “If you want to know what a man's like, take a good look at how he treats his inferiors, not his equals.”

  9. #9
    Both granite and float glass can bend a little. The thicker either is, the less that it bends.

    With granite, be sure that the back is as flat as the face. If it's not flat you can use thinset or leveling compound to support it from bending or better, move on to another piece. In years past, granite was cut with wire saws and the thickness was very inconsistent. In the last few decades, they have moved on to diamond gang saws that produce a much more consistent thickness. It's not perfect, but, it's much better.

    Your 1 1/2" thick pieces should be great for flattening your planes. I use a 12" x 24" x 3 cm piece of granite for flattening. I'm in the business, so I was able to select a piece that's consistently flat on both faces. Fortunately this was easy.

    Be sure to fully support your granite. While it seems stable as a rock (sorry for the pun), it can flex a little if not fully supported.

    Allen

  10. #10
    I'd be willing to bet more people knock their planes out of flat than ever make them better. It is too easy to be inaccurate. Leave them be unless you're 100% sure that they can not work as is.

  11. #11
    Quote Originally Posted by Rob Luter View Post
    Float glass can flex if it's used on a surface that's not flat. I use the top of my table saw and sandpaper for this purpose.
    Glass can flex quite a bit even if it's sitting on a flat surface. Surface plates are thick for a reason- to overcome flex

  12. #12
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    Quote Originally Posted by bridger berdel View Post
    Glass can flex quite a bit even if it's sitting on a flat surface. Surface plates are thick for a reason- to overcome flex
    I guess I'm not seeing how this can happen, unless the flat surface it's sitting on is also flexible.
    Sharp solves all manner of problems.

  13. #13
    Quote Originally Posted by Bob Leistner View Post
    I'd be willing to bet more people knock their planes out of flat than ever make them better. It is too easy to be inaccurate. Leave them be unless you're 100% sure that they can not work as is.
    Bob,

    I couldn't agree more. If you are sure the sole needs work your best bet is one of two things: Sell the plane to someone (not a friend ), or send it to a machine shop. Another option is to turn it into a roughing plane, scrub or jack. BTW, you should see the sole of my 30 year old wood stock scrub plane, ain't no way no how a metal plane sole could be a bad and it still works a treat.

    ken

  14. #14
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    A milling machine and fly cutter

    check to see if they’re flat before you work on them. How far out and where they are out matters. A touch up at the ends isn’t noticeable and I could live with the center slightly up on a long plane.
    Bumbling forward into the unknown.

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