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What Is The Correct Way To Measure A Marble?


jeroen
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Hello,

I have a marble for sale on ebay. It is 2-1/2 inch around the 'equator" as to speak, and about 2-7/16 measured over the pontil. So what is the correct size of the marble?

I have seen "cards/boards" with different size holes in it, to use for measuring the size of marbles. My idea is that with this system, the largest size of the marble is measured. As a marble is a sphere, and a sphere is an endless number of circles, it is impossible to squeeze a circle with a diameter of 2-1/2 inch through a 2-7/16 inch hole. So my marble won't fit in a 2-7/16 inch hole.

I look forward to your answers.

Jeroen

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Jeroen,

I think some of those templates you mentioned are made for drawing circles, in which case the actual diameter is slightly larger than what's stated, so as to compensate for the width of a pencil lead.

So your 2 1/2" marble may pass through a hole marked smaller than that.

I use cheap plastic calipers. Accurate, and precise to 1/128" or 0.05mm when using the vernier scale.

Best deal in this business.

http://www.ebay.com/sch/i.html?_sacat=0&_from=R40&_nkw=vernier+calipers&_sop=15

Hansel

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I didnt jump in as I have wondered also if handmades are measured pontil to pontil or equator to equator?

For measurement I use a caliper as well. Might I suggest a 3" model digital that measures in inches, and metric. The model is small enough to go anywhere as oppossed to the 6" model.

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Hello,

I use a caliper as well, I just saw some examples of those templates with holes, but still the questions is, is the size of a marble the largest one can find when measuring. Even at the equator the size differs a little. When a game fisher is measuring a fish he caught, he measures the largest he can find right? ;-)

Jeroen

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Hello,

I use a caliper as well, I just saw some examples of those templates with holes, but still the questions is, is the size of a marble the largest one can find when measuring. Even at the equator the size differs a little. When a game fisher is measuring a fish he caught, he measures the largest he can find right? ;-)

Jeroen

That's only because in his case, bigger is better. But if he were buying fish, surely he would prefer a more accurate measurement.

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My description would be:

Marble measures 2 7/16" but slightly larger from pontil to pontil at 2 1/2"

Okay my bad ....so the marble is a "smaller" diameter when measured from pontil to pontil?

Either way its still an easy fix on the description... just state as such......

Marble measures 2 1/2" but slightly smaller from pontil to pontil at 2 7/16"

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