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Thread: A Workshop Luxury- Build

  1. #1
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    A Workshop Luxury- Build

    Decided to spoil myself and free my snack table of those lumps of stone. Managed to find an attractive granite off cut the right colour. Price was right until I was asked if I would like the edges finished, which I answered with a casual “yes”. Seems that doubled the price.
    Well need some legs; lots of poplar lying around so after rough cutting and a good workout have some legs and stretchers.
    9A68F06B-E1B7-41E7-B81A-BC41C3DD69C0.jpg

    My plan was simple; top stretchers support the granite, bottom stretchers finish the structure.

    After struggling with the 100lbs of granite I rested the top on the legs:

    EB00CCBE-C9AD-4712-8205-7429E8567855.jpg

    Granite is supposed to be somewhat flat, so for fun I thought I would find out. Taking my good level out of it’s case I looked for light under the level. Sure enough there was light. My Lee Valley feeler gauges detected 10 thousands of an inch gap in the middle of the long dimension and oddly 12 thousands under the short dimension.

    Well it was either not flat or drooping under it’s own weight, or both. Lugged it onto the bench and repeated the exercise, both droops were 2 thou less. As I wanted a flat table this meant regular stretchers would not stop the droop. They would sag over time and restore the droop. This meant I was going to have to use the Kruksfeld/Matagomi joint!

    Before you rush to google, I made that up! Instead a 5th leg! Strong end grain to prop up a sagging middle.
    Challenges:
    Getting 5 legs sitting flush on the concrete floor.
    Making the middle leg ‘adjustable’.
    Pulling the edges down to the other 4 legs to achieve ‘flat’. Flat being a curve I could not detect.
    My planned drawer now has a leg in the way.

    Well another small workout and a fifth leg appears:
    1F192645-DE33-420C-8347-FEBF384B1867.jpg

    Let the fun begin:
    9E4304DA-BC56-4D86-9BBE-05CD420C47D2.jpg
    To be continued......
    ​You can do a lot with very little! You can do a little more with a lot!

  2. #2
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    Nice! Lie Nielsen sells one and they give accuracy specs. May be of interest for comparison. https://www.lie-nielsen.com/products...ches&node=4113

  3. #3
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    You might want to check Craigslist for something more robust.
    In my area granite surface plates are plentiful. I’ve even seen a few Craiglists post that were free if you can haul them away.
    Anyways I picked up a 24x36x4 inches thick for 180 bucks. It’s very handy to have nice flat area that’s pretty indestructible.
    Granite counter tops are not very flat.
    Aj

  4. #4
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    Yes Greg, I had looked at Lie Nielsen, their 2” top is flatter at the moment; also very heavy! On a flat surface mine is about 0.003” in 6”; but that is because of the ‘dip’ in the middle. Local flatness in 6” may well be similar if I can get rid of some or all of the ‘dip’. The fact that it droops 2 thou just under it’s own weight suggests I can get rid of at least 4 thou with persuasion. If that is the case then it will match Lie Nielsen.
    Andrew we don’t have bargains like yours around here but that is a monster to handle! For the number of times I tape abrasive paper to the top to flatten the bottom of something I wanted to keep the cost down.
    What I do like is the black as a sharpening background, with the right lighting it should make the bevels stand out.
    ​You can do a lot with very little! You can do a little more with a lot!

  5. #5
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    I have to ask the obvious question: why not build an apron with a center cross member and use four legs?
    Regards,

    Kris

  6. #6
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    Kris, I think the weight of the granite would sag the cross member in time. To flatten the top I may have to use anchors on the edges and use the middle leg as a fulcrum. The top stretchers will be used to anchor the edges. The only guarantee against sagging is end grain to the floor.
    ​You can do a lot with very little! You can do a little more with a lot!

  7. #7
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    I have to ask the dumb question: Why do you need that tight tolerance of flatness in the first place, especially over the entire surface area of a table?

  8. #8
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    Not a dumb question Steve, I’ve asked myself the same question! The only reason would be for trueing the bottom of longer planes. When doing the figure of 8 across the whole surface the ends would receive more pressure and curl up slightly, this effectively shortens the plane. For regular sharpening I’m sure it would make no difference at all.
    The other reason is just for my sanity, knowing it is flat!
    ​You can do a lot with very little! You can do a little more with a lot!

  9. #9
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    Granite plates are often found inexpensively. That LN table looks awful thin to me. Granite surface plates are thick so that they have the structure needed to retain their flatness spec.
    Bumbling forward into the unknown.

  10. #10
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    Most around here are very small, larger ones are expensive. It seems 2” is a very common thickness for the small ones. Mine is 9/8”, as I’m not a machinist I hope to achieve enough accuracy to flatten the odd plane. I would like a sharpening jig that runs on the marble so I can use the whole length of the sharpening stone.
    ​You can do a lot with very little! You can do a little more with a lot!

  11. #11
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    It’s not flatness for flatness sake, basically you can’t lap something consistently unless your doing so on a surface that is truly flat. Lapping a plane on something with a curve to it is going to produce a curved surface.
    Bumbling forward into the unknown.

  12. #12
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    Very true Brian. An 8 thou dip in a 24” granite slab is disappointing. I wonder if anchoring the edges to the leg stretchers with the 5th leg as a pivot will work to straighten it or just want to lift the legs off the ground. As a place for sharpening stones it works well with a black background. The only flat guarantee is a thick plate ground flat. When flattening is a very occasional thing the expense of such a plate is prohibitive. I have doubts that I can get most of the dip out and must devise a test.
    ​You can do a lot with very little! You can do a little more with a lot!

  13. #13
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    I dont think you'll be able to get any of the dip out of it, it will just stand on that center leg.

    I use a surface plate routinely in my shop, I have one small one basically for the odd chore then I have a nicer one for inspection. Most woodworkers aren't doing any inspection work, but I think they'd find a lot of use in the former. Sometimes have a perfectly flat surface is just exactly what is necessary when you need to double check something.

    Worth hunting craigslist and facebook until you find something good.
    Bumbling forward into the unknown.

  14. #14
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    If you go ahead with your current piece of granite you might get it to flatten enough by pulling the corners down and supporting the center. But with your 5 legged design you are expecting your floor to be flat enough or you will have to shim.

    Kris is on the right track with the x in the center but a cross would be as good and easier to make. Make it robust and it should not sag. But that misses another point. You may get better results if you plan to support the middle in several adjustable spots. You could make the adjustments with threads or with wedges. My preference would be wedges since they can be placed anywhere on the cross or around the perimeter apron.

    You can delete the lower stretchers since the upper structure will be plenty for a sharpening bench. Now there is room for a drawer as well.

  15. #15
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    You need three points arranged in a triangle to define a flat plane. Large granite surface plates rest on three points.
    To make use of four or five legs complicates things... a lot.

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