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Measuring A Clipped Planchet Error

 
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Author Previous TopicReplies: 6 / Views: 241Next Topic  
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79 Posts
 Posted 09/23/2020  09:27 am Show Profile   Bookmark this topic Add SensibleSal66 to your friends list Get a Link to this Message
Anyone know how to tell the % of clip. I have a scale , but whats the formula ?

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 Posted 09/23/2020  09:52 am  Show Profile   Check Yokozuna's eBay Listings Bookmark this reply Add Yokozuna to your friends list Get a Link to this Reply
You can get an accurate measure of the clip by weighing the coin. Then calculate that weight against the normal weight.
The first US coin motto was found on a 1792 half disme and read: "LIB (erty) PAR (ent) OF SCIENCE & INDUSTRY"


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 Posted 09/23/2020  09:58 am  Show Profile   Bookmark this reply Add SamCoin to your friends list Get a Link to this Reply
What you want to know is two times the circular segment bounded by the chord connecting the end points of the clip on the perimeter of the coin. The formula for a segment is (theta - sin(theta))/2 *r^2, where r is the radius and theta is the angle formed by the end points of the clip measured at the center of the coin, so multiplying by 2, we get just (theta - sin(theta))*r^2. Since the theta might be hard to compute compared to the length of the chord, c, we also know that the chord length is given by c = 2r*sin(theta/2), so solving for theta, we get theta = 2*sin^{-1}(c/2r). We can then plug that into our theta from the first equation to find the missing area, and then divide the missing area by pi*r^2 to get the ratio of missing material to the whole coin.

Edit: lol, or do what Yokozuna says. I feel like there's a "mathematician, a physicist, and an engineer are all going to the same conference" joke in here somewhere...
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Edited by SamCoin
09/23/2020 10:02 am
Valued Member
United States
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 Posted 09/23/2020  10:07 am  Show Profile   Bookmark this reply Add SensibleSal66 to your friends list Get a Link to this Reply
Yea ok, I think need a drink now . lol
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Australia
17414 Posts
 Posted 09/23/2020  10:36 am  Show Profile   Bookmark this reply Add sel_69l to your friends list Get a Link to this Reply
Sometimes the Blakesley Effect can be faked by flattening the rim on the opposite side to the clip.

Instead, check the edge millings opposite the clip.
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 Posted 09/23/2020  8:55 pm  Show Profile   Bookmark this reply Add Conder101 to your friends list Get a Link to this Reply
This brings up an interesting question. Just exactly what do we mean when we are measuring the "percentage of the clip"? Is it a determination of what percentage of the coin is missing? Or is it the percentage of the diameter of the coin that is missing? They are not the same thing.

Imagine a clipped planchet error where the "clip" passes through the exact center of the coin. The clip has removed 50% of the diameter of the coin. Would we call this a 50% clip?

But by weight MORE than 50% of the coin still remains. If we measure the percentage by weight, the clip would have to remove something like 60% of the diameter of the coin to be a 50% clip.
Gary Schmidt
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 Posted 09/23/2020  9:05 pm  Show Profile   Check Yokozuna's eBay Listings Bookmark this reply Add Yokozuna to your friends list Get a Link to this Reply
Please post the weight. I'll do the calculations and post the results. I would have just posted the equation, but I don't have it written down. Once I remember it THEN I'll make sure and post it.
The first US coin motto was found on a 1792 half disme and read: "LIB (erty) PAR (ent) OF SCIENCE & INDUSTRY"


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