A way to check the accuracy of your scale

[tmccray45]

As I'm weighing my powders, I often wonder, "How do I know that my scale is accurate?"  Sure, I've been assured by the manufacturer that it's accurate down to the weight of a gnat's eyelash, but how do I know?

"I know, I need a standard of some sort that I can use to check the scale."   But, what to use?   I know that the French are not going to ship the International Prototype Kilogram (IPK) which is stored in a vault in Sèvres, France, so what can I use that is fairly easily obtained?

Got to thinking about it . . .

Then, how's about good ol' American coins?   I bet the U.S. Mint has standards that are fairly accurate for our coins.

Sure 'nuff, if you go to the "specifications" page of the U.S. Mint, you can find the weights of the various coins we use.   The United States Mint Specifications page can be found at:

http://www.usmint.gov/about_the_mint/?flash=yes&action=coin_specifications

The coin weights are given in grams, so to convert grams into grains, you multiply by 15.4323584.  Given that, you find that:

Penny = 2.500 grams = 38.58 grains
Nickel = 5.000 grams = 77.16 grains
Dime = 2.268 grams = 35.00 grains
Quarter = 5.670 grams = 87.50 grains
Half Dollar = 11.340 grams = 175.00 grains
Presidential $1 = 8.100 grams = 125.00 grains

Of course, you should select newer coins with a minimum of wear in order to come closest to the standard weight, but using these coins, you can come pretty darn close to checking your scale.

[MZ5]

Thanks for the handy link.  Have you check-weighed any coins yet, to see what the coin-to-coin deviation is?

[Blackhawker]

Coin densities change by year as different alloys are used in order to save $$$....believe it or not.

Save yourself a ton of pain and just buy yourself some calibration weights.  Lyman sells a nice set with a 50 grain, two 20 grains, one 10 grain, a five, two 2's, a 1 grain and a half grain weight.  I think the set sells for about $30.00 from Midway.

[Blackhawker]

Thanks for the handy link.  Have you check-weighed any coins yet, to see what the coin-to-coin deviation is?

Good point!  Coins get dirty, dented and chipped.  There IS deviation....how much I cannot say off hand.  I don't think I'd feel safe with known deviations in my calibration checks when I'm touching off loads right next to my face.   

[billy_56081]

Silver coin 50 lb per 1000 dollars. If not worn.

[necchi]

I mentioned this in another thread, My work has a really spendy, accurate electronic scale,. A pubic hair WILL put #'s on this scale.
Just because I could, I weighed a random nickel, dime, and a quarter I had in my pocket and did the conversions so I could have something to verify my scale; here's how mine compare to the "standard"

   (standard)                                          (mine)      (+/- rounded to .01)
Nickel = 5.000 grams = 77.16 grains-------78.08592---,+.93
Dime = 2.268 grams = 35.00 grains--------34.722---,,,,-.3
Quarter = 5.670 grams = 87.50 grains-----87.9624---,,,+.46

 Now, even the best with the Dime is 3 tenth's off the standard, and that way far to set the scale on for calibration to compare to the "book" weights listed by manufacturers.

 I'm not concerned that MY scale weigh's the same as the manufacturers scale to a tenth of a grain. I am concerened that my scale will weigh what ever charge I have worked up to be accurate in my gun,,,and then REPEAT  that weight each time I set my scale 
 I do have those three coins set aside, with their weight, and use the quater mostly to set my scale the same each time, then put the dime on it to see if it still tips the same.

[JustaShooter]

Just remember, before 1982 when the pennies were 95% copper they were 3.11 grams.  Also, I think the mint allows .5% tolerance, and of course there is always wear to reduce their weight and and grime to increase it...

Just a Shooter

[billy_56081]

I'm kinda lucky, I have test weights from 1 gram to 500 lb all certifed in a metrology lab annually.

[buck460XVR]

 I'm not concerned that MY scale weigh's the same as the manufacturers scale to a tenth of a grain. I am concerened that my scale will weigh what ever charge I have worked up to be accurate in my gun,,,and then REPEAT  that weight each time I set my scale 

..................bingo!

[Slowpoke Slim]

I bought the Cabela's "deluxe" check weight set. It has weights from .5 to 500 grs. I verify my calibration is right each time I turn on my scale and "calibrate" it.