Measuring "squareness" Accurately

Get some butcher paper or equivalent. For the tube in question. VERY carefully layout the width and then the circumference length on this paper. Next, cut this out as a template. Tightly lay this paper onto the outside of the tube, taking extra care to make sure the two ends of the papers width line up with each other. Note the discrepancy if any about the edge of the papers width and the tube ends…Dave.
 
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all you need is a counter top next to a wall or something...if it is square on the end it will sit against the wall the same as you turn it
 
SQUARENESS OF THE HOUSE DOESN'T MATTER. YOU ARE ONLY LOOKING AT GHANGE IN GAP FROM THE WALL
 
We use very similar CF tubes for high power rocketry. Most are spiral wound on a polished aluminum mandrel, then ground smooth on the outside. Some companies cut them just like parting off a piece, but with an abrasive disk instead of a parting tool. When that's done they end up "square enough" for our rocketry needs.


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I was finally able to set up a test using a granite gauge plate and precision square. This tube has been cut very square. I measured each end at 4 places, 90 degrees apart. I shined a small LED light behind the square to better see any gaps. Not perfect, but I was not able to get a 0.010 feeler gauge under any single gap.

In addition, there will be a final adjustment possible. By using very thin paper shims under the front corrector plate optics, very precise optical axis adjustments can be made

shim.jpg tube square check.jpg
 
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