# Checking "trueness" of X-Y table

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What is the best way to check how straight X-Y travel is and how square the axes are? I have both a travel dial indictor and digital caliper at my disposal, would these be of any use?

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A test I do is to mill a ring at constant Z on the top of a piece of scrap aluminum. I then put the spindle over the center, and sweep the ring with an indicator on a flexible arm connected to the spindle. (Import copy of an Indi-Col.) This measures perpendicularity of the spindle to the axtual XY plane of motion. I eventually end up with a saddle due to wear of my X and Y axes. This is more accurate than just assuming the table top is parallel to the XY plane of motion.

Jon

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snipped-for-privacy@hotmail.com (oparr) wrote in news:43650b7.0409221152.42eb61f1 @posting.google.com:

One method of doing this is a sacrificial piece of soft material like aluminum. Use a short, stiff end mill and machine a square corner, then check the part. I would machine at least a 4" length.

Another method would be if you had a known good square. Put the dial indicator in the spindle, align one side of the square using an indicator. Check the other side, repeat aligning off the checked side, and verify your measurement on the first side.

Neither of those will get you straightness, only squareness.

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Thanks guys. At this point I'm thinking of chucking a ball point pen, "drawing" on paper using the table and checking the angle against a reference square.

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Indicate a piece of stock in x, then make a cut in y.........

Then flip it over and indicate it along x again..........now indicate the cut you had previously made in y, your measured runout is twice the out of squareness amount in x y...

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