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Outer Diameter from Torus


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Hey Gang,
I need to measure 2 surfaces on a torus feature and need to report the out diameter. If I measure it as a circle, I can't guarantee I am on the equator. I am considering measuring it as a torus or freeform surface and then recalling the points into a circle or cylinder and evaluating the diameter using Outer Tangential, in hopes of finding the highest points on the apex. I'd like to hear your thoughts and ideas.
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Could of thoughts:

First one would be, could you scan a curve from the top to bottom of the Torus, report the max point (which would give you the equator), and then use that point to measure your circle at the equator?

Second, could you do a curve distance where you measure the two ends from top to bottom?

There seems to be a lot of ways you could attempt this.
On your second one, could you just not do a result element calculation difference between the d1 + d2? Or are you trying to actual measure it?

I've had to measure a lot of ball races, and for me, the best thing that worked was measuring a circle on the short arc side to grab the Z location, and then measuring the equator with the known Z value.

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We're trying to sell Yasda CNC Mill and are doing a test cut to show the machine can make the part. I'm using our Prismo Ultra to prove the machine can make the part. I'm guessing customer probably has gages but I don't know if anyone asked. lol
Usually, when I have to measure a diameter at the equator of a torus, I measure the feature as a taurus, and put it in a secondary alignment (filling in X, Y, Z origins only). Then, I measure the diameter as a circle path, using the secondary alignment at it's origin. This usually gets me within 1 micron of a calculated diameter, based on the torus (using D1 & D2), of a well formed part. Given the small area that you are looking to measure, I would consider using an L1 evaluation (In my experience, it usually gives you a more accurate size, when there isn't a lot of surface to evaluate), at least for the torus, to get your location
The way I understand it, L1 (least absolute value) is a simpler (more direct) calculation method than LSQ.
I did a comparison between LSQ & L1, vs measuring with a a linear trace on a MarSurf LD 260.
LSQ consistently gave larger results, while there was good correlation between L1 evaluation and the Mahr.

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Ken suggested making an alignment from the torus and then measuring the circle from that alignment, which I am going to try. Though I think Richard's suggestion of XXX ring gages would produce the most reliable proof. I just didn't think about this early enough to get them on order.
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