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  • Flat Glass

    Would two 1/8" pieces of glass, maybe mounted on 1/4" hardboard, be strong enough and safe enough to use as a flat sharpening surface? The hand sharpening systems you buy use 1/4" plate glass. I suppose that's made differently from regular window glass? I have some medium size window panes and I have a plane I'm trying to revive.

  • #2
    Re: Flat Glass

    I would suspect the 1/4 in plate used in the systems are tempered, hence quite a bit more resistant to breakage, I have worked with various glass extensively and would be concerned that using normal 1/8 doubled would be quite a bit more fragile and susceptible to breakage. In addition, even with the hardboard you will have small movements between the two panes of glass.

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    • #3
      Re: Flat Glass

      go to a glass shop and see if they have any scraps,

      I have taken out large double pane windows that were 1/4 glass and not tempered, and could cut it with a glass cutter and snap it,
      Push sticks/blocks Save Fingers
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      • #4
        Re: Flat Glass

        or you can get a foot by foot granite or marble floor tile. Those should be flat enough. I wouldn't count on 1/8 glass to be rigid enough.
        In order to understand recursion, one must first understand recursion.

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        • #5
          Re: Flat Glass

          Thanks!!! All great tips. In the interest of keeping all appendages attached and all fluids enclosed, I'll save the glass for something else.

          I have a piece of industrial grade laboratory counter top that is "practically" flat. I can see a hint of light under my Starrett ruler in one direction and none in the other direction. Is that flat enough? The material itself is dense and inert. I suppose it depends on how much swale there is in surface. If I were to put a number on it, I'd guess it'd be about a millimeter. Hey! I'm going to HD, this is an excuse to get a set of feeler gauges. And if they don't have them, there's an AutoZone on the way home.

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          • #6
            Re: Flat Glass

            IMO it's flat enough.
            I saw people on wood working forums worry about panel glue ups after they saw the glue joints with 5000X magnification. To them few things would be flat enough.
            In order to understand recursion, one must first understand recursion.

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            • #7
              Re: Flat Glass

              I measured the gap to be less than .002". Most references suggest that is adequate for woodworking purposes. On the other hand, I'm not dealing with wood here, it's metal. Is a .002" tolerance OK on a cutting edge? Or on smoothing the bottom of the plane?

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              • #8
                Re: Flat Glass

                Is that 0.002 over 12" or per inch? over 12 - plenty flat, per inch well since most of your tools awill be less than 2" likely plenty flat as well.
                Typically lapping plates are dead flat as in 0.001 over 12".

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                • #9
                  Re: Flat Glass

                  It's over 12" so I'll live with it, for now. When I invest in some quality tools, I'll invest in some quality maintenance.
                  Last edited by masww1; 07-24-2009, 02:59 PM.

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                  • #10
                    Re: Flat Glass

                    I'm a little late here, so this is probably of no use... but, instead of glass, I use a piece of granite tile. I suspect it's as flat as glass and certainly it's a lot more sturdy.

                    For what it's worth,

                    CWS

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                    • #11
                      Re: Flat Glass

                      Where'dja getit? Granite tile like floor tile? I live in a large enough city there are several stone manufacture and installation businesses from which to choose. Would scrap pieces be flat enough? I wouldn't want to have to buy a box of tile. Wonder what one square foot of granite ought to cost? It's about $20 in the WW catalogs.

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                      • #12
                        Re: Flat Glass

                        Actually, I bought it at Home Depot! In the future home, we ripped out the old, beaten oak parkay in the foray and put in black granite. Also faced the fireplace with it too. I have a carton left over and a few pieces that were left from the cutting.

                        I had found the same product about three years ago at a local discount building supply place up here, they wanted $10 a tile (1 sq. ft.). At the time, Home Depot wanted quite a hefty price. But about the time we were ready for the project (two years ago) Home Depot started stocking the tile and the price dropped significantly. I think I ended up buying it at about $90 for a box of 10 tiles. At the time, the sales associate told me the earlier, higher price was because it was special order and that now that they were stocking it, they could give me the lower price.

                        I'm not sure if they still stock this particular style (polished black granite), but I could check. You really don't need any special color and I think all the granite tile is polished. I would think marble would also be okay, but I'm not sure if it's as smoothly polished as the granite.

                        In any case, check with your local tile or building supply stores. Most places that sell this kind of thing would surely have broken cases. For sharpening, all I use is a 4" wide piece that is 12" long. Works quite well for my needs.

                        I hope this helps,

                        CWS

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                        • #13
                          Re: Flat Glass

                          I just picked up 2 1 foot square granite tiles at lowes today, for the big price of $2.99 each, so 2 square feet for $5.98 it is about 1/2 in thick and polished on one side.

                          Dp

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                          • #14
                            Re: Flat Glass

                            i just use MDF or a 12" ceramic tile

                            it really doesnt need to be THAT flat to get the job done. if you HAVE to have granite just go to one of the borgs and get a granite tile for a couple bucks it will be fine

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                            • #15
                              Re: Flat Glass

                              Disclaimer: I use a granite block flattened to <.001" over 12". I have it, I use it, and it just fits perfect under a full sheet of wet/dry abrasive.

                              However, I just wonder how those guys in the 1700's and 1800's made fine furniture without tools to measure in the thousandths of an inch and 2000grit wet/dry paper. They sharpened their irons with Washita stones, waterstones, carborundum, etc and stropped them with leather strops.

                              They made their straight edges by matching three different board edges until light would not shine between a match of any of the three. Their stones were flattened by rubbing against each other until the straight edge showed they were flat. In reality, "close" was plenty good, joints were custom matched, and surfaces were flattened and scraped until they looked good to the eye.

                              Few tools were ground with an edge that was to thousandths tolerance, which is a ridiculous standard concerning hand tooled wood working, when the wood will move more than that in a day's humidity change.

                              A piece of float glass like the glass shelf from a medicine cabinet is quite flat enough to sharpen a plane iron or chisel. Same for a broken piece of polished granite from a ruined tombstone, a sink cutout from a corian counter top, or, for that matter, a sink cutout from a factory particle board formica-type top will also work. If using wet/dry paper, any flat non-porous surface will let a spritz of water "glue" the paper to the surface while you sharpen.

                              JMTCW

                              Go
                              Practicing at practical wood working

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