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Thread: checking a block for square, etc?

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    ScrapWood is offline Aluminum
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    Default checking a block for square, etc?

    I recently squared up a 4x4x8" block of alum., and I'm not sure how to really inspect it. I have a surface plate, hgt guage/indicator, stl angle plate, and of course, mics in this range to work with.

    I get how to do parallel, but squareness and perpendicularity? It's looks good pushed up against the angle plate, and that's fine for the simple drilling fixture I'm making, but would like to know what the numbers are.

    Had problems with search, never seem to know what to look for.

    Any suggestions or a helpful previous post maybe?

    Thanks, Walt

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    buckeye's Avatar
    buckeye is offline Plastic
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    You need a squareness checker, It looks sort of like a surface gage, except that the beam is fixed square to the base. There is also an indicator holder that travels up and down the beam, place an indicator in it and run your indicator up and down against the workpiece. In a pinch I've also used an angle plate or solid square and a piece of rolling paper or .001 shimstock. Butt your work up to the corner of an angle plate and try getting a piece of shim between them at the top and bottom.
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    A cylinder square is appropriate for this type of test.

    They're quite accurate, and not terribly expensive.

    Put the work against the cylinder square and check for gaps, with a flashlight if the
    work is of sufficiently high precision, otherwise with feeler gauges.

    Some cylinder squares have one end slightly off-square, with calibration lines running
    around the cylinder. These are used to determine the actual anglar error.

    - Leigh

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    A cylindrical square, a square-all and test indicator will tell you all you need. They work fantastic together.
    Dave

    http://www.mscdirect.com/
    Last edited by SchneiderMachine; 02-09-2012 at 08:46 AM. Reason: tracker removed (link dont work anymore, fix it Leigh, you broke it)

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    Last edited by The real Leigh; 02-08-2012 at 09:44 PM. Reason: Link verified OK

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    ScrapWood is offline Aluminum
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    Thanks Buckeye and -Leigh

    The cylinder square might be in the cards with the buyer. Wow, forget about the feeler guages in my box! Oops! Even with the angle plate, better.

    Like the info about the off-square ones!

    Thanks for the links Dave,


    Walt

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    winger is online now Hot Rolled
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    Default

    Another pertinent thread to read:

    Checking a square and angle plate


    Dave
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    FranH is offline Hot Rolled
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    Smile squareness

    Let us assume that all surfaces are parallel within.000000. (which also means they mic the same thickness) Just rotate the indicator 180 degrees and measure from the back.....

    Put the back (heel) of the surface gage against the part, put the indicator near the top of the vertical edge (the same surface the surface gage is butted against), establish a zero reading.......without moving the indicator push the surface gage against the opposite side and if the reading is 000 the vertical surfaces and the surface on the plate are 90 degrees.

    Visualize a 5 degree parallelogram resting on the plate.... as you can see the indicator reading would show double the error when the reading against the vertical surfaces as one side tilts toward the indicator and the other side tilts away when the surface gage is butted against them.
    Last edited by FranH; 02-09-2012 at 08:01 PM. Reason: explain better

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    ScrapWood is offline Aluminum
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    Quote Originally Posted by FranH View Post
    Let us assume that all surfaces are parallel within.000000. (which also means they mic the same thickness) Just rotate the indicator 180 degrees and measure from the back.....

    Put the back (heel) of the surface gage against the part, put the indicator near the top of the vertical edge (the same surface the surface gage is butted against), establish a zero reading.......without moving the indicator push the surface gage against the opposite side and if the reading is 000 the vertical surfaces and the surface on the plate are 90 degrees.

    Visualize a 5 degree parallelogram resting on the plate.... as you can see the indicator reading would show double the error when the reading against the vertical surfaces as one side tilts toward the indicator and the other side tilts away when the surface gage is butted against them.
    I get that suggestion!

    Works with what's around here now, 'though I love to hear about the other angles of attack and the bigger picture on this.

    Makes sense for the tightness I need for the odd job coming through. Just don't know why the error should be halved instead totaled? I must be confusing squareness and perpendicularity to the srface plate.

    Is this the case?

    Walt

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    onemanshow is offline Plastic
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    Check it in the machine. It is what I do for fast checks. your X,Y,Z axis should be square to one another.
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    ScrapWood is offline Aluminum
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    Thanks onemanshow,

    It's usually square,

    That is when I remember to check tram after a yanking the quill out about .400 'instantly' while plunging a 15/16 emill into leaded ni-silver brz.

    Yeah, yeah, I know you have to stone the end of the tool.

    In March I hope to get an Indicol / lndicator setup. I want to get a decent one so it's worth waiting.

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    Here a video demonstrating a squareness check with a surface gauge/indicator. One could be made easily. However, what he does not mention is that you need a good square to calibrate.

    How To Check A Block For Squareness - YouTube

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    dazz is offline Hot Rolled
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    Hi
    So if you need an accurate square to use the surface gauge/indicator, then how do you prove squareness?

    From what I have read, the cylinder square is "proveable" in that it is easy to prove that the cylinder is a cylinder by simply measuring the diameter along the cylinder length.

    The base must be square to the cylinder axis because of the way a lathe works. So it should be possible for a modestly equiped workshop to produce an accurate cylinder square with some care (or just buy one). That and a surface plate would provide a reference to set the surface gauge/indicator.

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    As with any precision measurement, the question is not "Is it square?" but "How square is it?".

    - Leigh

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    lazarus is offline Hot Rolled
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    4x4x8 block, measure edges diagonally. If all match their corresponding alternates it's perfect.

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    gbent's Avatar
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    Measuring diagonals works great for squaring up building foundations. On machined parts, its to susceptible to the unevenness of deburring the corners.

    Reconfiguring the surface gage to use the ball end and a dial test indicator is the fastest method with ordinary shop tools. It reads directly rather than cussing shims.

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    lazarus is offline Hot Rolled
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    I was going with what the OP said he had on hand. I hope he has a v-block. Then the height gage and surface plate would work easy. Yes when you debur it things will change. But then again if all read the same you did a hell of a job of hiding an out of square situation.

    Probably many different ways, I just got a visual of what he said he has to work with and ran with it.

    Ben

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    Quote Originally Posted by lazarus View Post
    4x4x8 block, measure edges diagonally. If all match their corresponding alternates it's perfect.
    Sorry but that won't work.

    All it tells you is that the measured diagonals are equal at the respective points of measurement,
    provided the instrument line of pressure is parallel to the diagonal,
    and further provided that the end-point radii are identical and square with the piece.

    The sides could be significantly off-parallel.

    - Leigh

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    neilho is offline Hot Rolled
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    Quote Originally Posted by The real Leigh View Post
    As with any precision measurement, the question is not "Is it square?" but "How square is it?".

    - Leigh

    Now we're gettin' to it! And then, "How square does it need to be?"

    The surface gage/test indicator on surface plate works well for tooling, but for most parts a good square with a strongly lit, white background suffices.

    Neil

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    easymike299 is offline Aluminum
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    This might make it easier to visualize.
    Attached Thumbnails Attached Thumbnails squar1.jpg  
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