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Cheap Scale Calibration Check

Before doing another spring constant test with the old Harbor Freight scale, I found deployed my cheap calibration weight sets to verify it displayed the right numbers:

US-Magnum Scale - calibration check

US-Magnum Scale – calibration check

It’s spot on for all weights above 1 g, although I must tap the pan to settle on the reading from above for it get the last 0.1 g right.

Below 1 g, it’s the wrong hammer for the job; I expected no better from it.

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  1. #1 by RCPete on 2018-10-25 - 10:27

    If you need accurate values below 1 gm, a powder scale would do the job. I haven’t hand loaded in ages, but the beam type was good below 1 grain (approx 1/15 gram), and there are electronic scales from the usual suspects. No idea if they’d have SI units, or if you’d be stuck with grains.

    • #2 by Ed on 2018-10-25 - 14:56

      There’s a balance-beam powder scale in the heap, but it’s nowhere near convenient enough for anything other than powder!

      Should I ever need a scale in that range, I’ll get something electronic with a flat pan instead of a hanging basket.

      • #3 by RCPete on 2018-10-25 - 20:07

        RCBS has a flat-pan electronic one for about $150. Grams and grains, and two 50gm calibration weights are included. They also have a set of calibrated weights. Batteries or wall-wart power supply. I noticed it has a 15-20 minute warmup time. Makes sense for such a small weight.

        I have the beam powder scale, but when I was doing pistol, I’d use a fixed-cavity powder measure (the RCBS Little Dandy). It was wonderfully repeatable.

        • #4 by Ed on 2018-10-26 - 11:18

          Measuring by fixed volumes has a lot to recommend it, particularly for granular material. Electronic strain-gauge balances seem to update in discrete (and sometimes nonlinear) increments while a (slow) stream adds to the pile.

          I gotta get back into punching paper …

  2. #5 by Vedran on 2018-10-25 - 11:55

    I have a 300g max, 0.01g cheapie that seem to do the job just fine. I keep it in g of course, but it does other units, including pcs for counting stuff like M3 nuts in bulk. I regularly mix 1g epoxy batches – yes I’m that frugal or maybe I could sell it as environmentally conscious :)

    • #6 by Ed on 2018-10-25 - 14:58

      This one can count, too, but has trouble with units weighing less than a few grams. Cutting the range down from 1 kg and increasing the resolution would definitely help.

      And, yeah, mixing small batches of epoxy by weight is the only way to get it right!

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