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# Difference between algorithms3

## Difference between algorithms

(OP)
Does anyone knows what is the difference between outer tangential and minimum circumscribed/maximum inscribed cylinder algorithms on a CMM?
In other words if a hole is scanned/measured for size and two different algorithms are used to report the size (outer tangential AND maximum inscribed cylinder) would be a difference between the reported sizes? If yes, where the difference is coming from?

Thank you

### RE: Difference between algorithms

You might get a better response by posting here -> forum286: QC, Inspection & Testing engineering

"Know the rules well, so you can break them effectively."
-Dalai Lama XIV

### RE: Difference between algorithms

3
gabimot,

Outer tangential is a general term, that can apply to different types of geometry. An outer tangential algorithm finds the perfect geometric feature (plane, cylinder, or other) that just touches the "high points" of the actual feature (or the points measured on it). "Outer" in this context means external to the material. So a high point plane would be an example of an outer tangential feature. A maximum inscribed cylinder would be an example of an outer tangential feature for a nominally cylindrical hole, and a minimum circumscribed cylinder would be an example of an outer tangential feature for a nominally cylindrical pin. For datum feature references at RMB, the datum feature simulator is generally comprised of outer tangential geometry.

So for a hole, the outer tangential and max inscribed CMM algorithms should give the same result. For a pin, the outer tangential and min circumscribed algorithms should be the same.

Evan Janeshewski

Axymetrix Quality Engineering Inc.
www.axymetrix.ca

### RE: Difference between algorithms

(OP)
Evan,
Thank you very much for the clarification.
Should I understand that the other boundary/algorithm is called "inner tangential" and is used when features at LMC/LMB are measured/calculated?
In other words when UAMME (unrelated actual minimum material envelope) and RAMME (related actual minimum material envelope) are needed the "correct" algorithm to be used is Inner tangential?

Thank you

### RE: Difference between algorithms

gabimot,

Yes, I believe that "inner tangential" would correspond to the other boundaries that are inside the material.

Evan Janeshewski

Axymetrix Quality Engineering Inc.
www.axymetrix.ca

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