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  • Checking Flatness

    I've been using the corners of three 1-2-3 blocks set on my surface plate to check the angle plate I'm trying to grind flat and square. I tried to use 3 jack stands that have points but the adjustment is too coarse. What do others use to check for flatness?

  • #2
    would 'parallels' be too easy an answer?

    I've used several on the plate to check a plane with
    a protruding feature before. It's not the most precise,
    but it works fine for things like car bellhousings...

    t
    rusting in Seattle

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    • #3
      Can't you just sweep it with an indicator on a suitable ground base. I do on my surface table...
      Last edited by lakeside53; 03-01-2009, 03:25 AM.

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      • #4
        Check with Evan. He had a way of checking flaness using a laser.

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        • #5
          "would 'parallels' be too easy an answer?"

          Yes, because I'm looking for just a small point of contact in three places.

          "It's not the most precise, but it works fine for things like car bellhousings..."

          I need to be precise. Surprised others haven't commented as I would think this is a common situation for many machinists.

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          • #6
            3 Point plane by 3 ballglides.

            Originally posted by Neil Jones
            I've been using the corners of three 1-2-3 blocks set on my surface plate to check the angle plate I'm trying to grind flat and square. I tried to use 3 jack stands that have points but the adjustment is too coarse. What do others use to check for flatness?
            Some thing along these lines may help.
            Plane established with three 0.7500" dia balls.









            Sleeves made of 1" dia delrin, snap over ball, to keep from rolling too much on table.
            Vee blocks keep stock from rolling around.

            As you are grinding angle plates, Blue the surface?

            Cheers,
            Les H.
            The Impossible Takes Just A Little Bit Longer!

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            • #7
              Yes, because I'm looking for just a small point of contact in three places.
              Heh, 'use ball bearings' was a drop-dead obvious answer.

              Less obvious was putting them in those little sleeves, which is clever.

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              • #8
                You can drop them into a washer, too. So long as they don't roll away while you're using them any retainer will work. But I really like the plastic tubes.

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                • #9
                  I would think ball bearings would also work well. As for 1-2-3 blocks, they come in matched pairs, but the third one may be off by quite a bit unless you carefully select it.
                  Paul A.

                  Make it fit.
                  You can't win and there is a penalty for trying!

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                  • #10
                    neat idea Wes
                    .

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                    • #11
                      When I ran a surface grinder we had to hold .0005 + or - .0002 flat.We made a 3 legged leveling table (brown and Sharp offers one) it has 3 leveling screws that are 3/8-40 same as a mic. Level a point at each leg to "dead nuts" zero then place the part on the table and sweep with an indicator to check how flat your part is.If you just set parallels,123 blocks or what ever on a surface plate all you have checked is that your part is parallel to the surface plate.Just because something is paraellel does not mean that it is flat
                      most of the time it is but not always

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                      • #12
                        Thanks, Les.

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                        • #13
                          "(brown and Sharp offers one) it has 3 leveling screws that are 3/8-40 same as a mic."

                          Got a link? I'd like to have a look/see.

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                          • #14
                            I found something called a "Leveling Plate" in an old Brown and Sharpe catalog I had buried in the garage. It's described as "pivots on one point with two fine- pitch micrometer-type leveling screws to provide a solid 3-point bearing." It's got a hardened and ground work surface. The picture in the catalog shows a workpiece on the hardened and ground leveling pad sitting on what looks to be two gage blocks.

                            For the life of me I can't figure out how this device works or how it would be better than the 3 ball bearings that Les suggested for indicating flatness.
                            Last edited by Neil Jones; 03-01-2009, 07:55 PM.

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                            • #15
                              It's adjustable. For different purpose.

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