Calibration Weights Needed
- Thread starter South Pender
- Start date
That they are, I've had Lyman ones for 30yrs or so. Apparently needed a 100gm one for the A&D, so picked up a chinese one, it shows 154.32 on the A&D, just like it was supposed to, so do the pair of RCBS 50's I have. All the small Lymans I have plus the cheap chinese ones I have read right too. As long as it is repeatable on the second digits all the time, I'm not going to worry about it.
Thought I'd check back in on this thread. After giving this some thought, I decided to look for a really accurate calibration weight and bought a 10 g. (154.32 grains) weight that has F2 accuracy. This accuracy level is ±.6 mg. or ±.009 grains sensitivity. These really sensitive test weights can be quite expensive, but I found mine at Transcat for $45, the lowest price I could find. Just thought I'd pass that along.
Before I got a premium scale I used to make my own test weights.
Real simple, I would take a piece of brass sheet metal and stamp the charge weight into it, then trim it to weigh the same as my weigh pan plus the powder.
From that point on I had a test weight that matched what I was after. I would just compare the charge in the pan to the test weight. If they agreed, I was good. If they didn't, I fixed the charge.
If I wanted to change the charge weight, I would just make sure my charge weight was lighter or heavier by the amount I wanted as compared to the test weight.
While such a method will not help you calibrate your scale, it will ensure your loads are always the correct weight anyways assuming you continue to use the same weigh pan.
Be careful though because once you start using this method to validate your weights, you will come to find disagreements between the scale reading when you alternate back and fourth between the charge and validation weight. Once this happens, you will become acutely aware of the inaccuracy of your scale and you may find yourself trying to justify the cost of a much better scale. That's what happened to me and why I now have an internally calibrated analytical balance that I can trust.
Real simple, I would take a piece of brass sheet metal and stamp the charge weight into it, then trim it to weigh the same as my weigh pan plus the powder.
From that point on I had a test weight that matched what I was after. I would just compare the charge in the pan to the test weight. If they agreed, I was good. If they didn't, I fixed the charge.
If I wanted to change the charge weight, I would just make sure my charge weight was lighter or heavier by the amount I wanted as compared to the test weight.
While such a method will not help you calibrate your scale, it will ensure your loads are always the correct weight anyways assuming you continue to use the same weigh pan.
Be careful though because once you start using this method to validate your weights, you will come to find disagreements between the scale reading when you alternate back and fourth between the charge and validation weight. Once this happens, you will become acutely aware of the inaccuracy of your scale and you may find yourself trying to justify the cost of a much better scale. That's what happened to me and why I now have an internally calibrated analytical balance that I can trust.
To internally calibrate your balance, you would need a calibration weight of a known, precise value, wouldn't you? Perhaps this goes without saying, but if you have a calibration weight that is precisely X grams or grains within a tolerance range of, say, ± .2 mg., a really good balance could be calibrated, or would be adjustable, to read that exact value when the calibration weight was put on the pan. Correct?
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Thats not good enough Bullet vary in weight. No a good idea at all.
Calibration weight are in gram because calibration mode on most scale are in grams.
Actually, it is more than good enough.
When a person is weighing a charge, it would not matter if the scale was off by (for example 0.4 grains) or dead on.
Assuming you always zero the scale first, and the scale maintains its 0.4 offset, (repeatability) you are always getting the "same" weight of charge even though it may differ from the scale reading by whatever the offset is.
So for example, you work up a load. You Start with 40 grains and go up by 0.2 grains.
Turns out 42.6 grains (on your scale) gives you a great load. (even though it is really not 42.6, its 43.0)
So you continue to make loads of 42.6 on your zeroed scale and they always shoot great.
In your load book you record the data as 42.6
See where this is going? The weight isn't the issue, the repeatability of the scale is the issue.
The absolute number reading on the scale doesn't mean anything, its a reference point, regardless of the actual weight.
Which is what I was hinting at in post 17
I could put a bunch of 155 grain bullets on a get weights of 155-155.4 and think, well, that's normal...bullets, nickels, whatever, it's plenty accurate
Your point is well-taken. However, after thinking about this for a while, I've come to the conclusion that I would definitely want to know the correct exact weight of my powder charges (or as close as is possible with the scale). Having what shows as 42.6, but, in fact unknown to us, is 43.0 is, as you say, probably no really big deal (although that depends on the actual discrepancy, and if it's greater than the .4 gr. you cite, it could be a big deal), but I'd definitely prefer my scale to show 43.0 (or perhaps 42.99 or 43.01) if 43.0 is the precise weight. The F2 class calibration weights get you to within .009 gr. tolerance, and if you want greater precision, the F1 class of weights will get you to within .003 gr. tolerance, but they can get pretty expensive.
With a good digital scale, you can calibrate the scale to be exact, but you need to know the precise weight of the calibration weight you use to do the scale calibration. You sort of say here's a weight of precisely 153.32 grains (10 g.) and you (the scale) must show precisely that weight. Once you've done this scale calibration, your scale is precise. I like to check that nothing has changed each time I start a weighing session by making sure the calibration weight produces its precise value on the scale before starting to weigh charges.
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I'm not sure what you are asking.
It's nice to have an expensive and extremely accurate scale, but I don't believe many guys on CGN have such a thing. My post was just to suggest that any given thing that weighs the same as your target weight can be used to validate the charge weight. It can be something as simple as a ball of tin foil.
If you put a weight on the scale that weighs X, then you put your weigh pan on the scale and add powder until it weighs the same as X, then regardless of how precisely your scale is calibrated, the weights are the same. If you alternate between the two, you should (in a perfect world) get the same value every time, but you wont.
I'm not suggesting that there is no point in ever calibrating your scale. I'm really idling toward the point that comparing a known and fixed weight to your charge is a nice way to see if there is an error in the repeatability of your scale. That is something guys need to keep an eye on as most scales are not as accurate as the typical consumer assumes. This exercise will illustrate that.
Sure, but what you are describing as necessary is consistency or repeatability. And I agree that this is important. However, if you can't be certain about the precise weight of the test weight, this is less than optimal. Your ball of tinfoil shows a weight of 60 grains on your scale and does so consistently, but in fact it really weighs 62 grains. If you then weigh a charge of powder until it registers 60 gr. on your scale, you're actually getting 62 grains of powder because your scale hasn't been calibrated. My question was more one of wanting confirmation about how a scale could be calibrated. And as I noted in Post #32 above, I think you'd want a precise calibration weight. I don't know whether a less-expensive scale like the RCBS electronic scale could be precisely calibrated, but something like the A&D FX-120i (which still falls short of your preferred level of precision) could be. So consistency is all-important, no question, but I'd want more than that; I'd want precision as well.
I use the two weights that came with my digital scale to calibrate it initially. Then, after it is calibrated, I have a 40 grain bullet I put on the scale, and it always weighs 40.0.
I've weighed it on a beam scale, and it also weighs 40.0 on the rcbs beam scale.
So, at least I know I am consistent, if not accurate to 0.1 grains.
I've weighed it on a beam scale, and it also weighs 40.0 on the rcbs beam scale.
So, at least I know I am consistent, if not accurate to 0.1 grains.
What is your calibration procedure? In other words, do you have to (or can you) make an adjustment to the digital scale?
- Location
- Nova Scotia
Most digital scales require a 50gram check weight to Calibrate.
I follow the instructions on the hornady digital power dump. It gives you an ok after you do each step, adding each cal weight, pressing a cal button, and then after a prompt, adding the next weight and pressing the cal button. After that, it gives you an OK and you start. Then you place the pan on the scale and hit zero, and proceed. After that, I place on my 40 grain bullet and just see if it still weighs 40.0, and it always does.
So basically, you calibrate with two known weights they supply (I believe a 10 gram and a 50 gram), then zero it for the pan you intend to use. My 3rd weight is something I do on my own just to see if it still reads 40.0 for my peace of mind. There is no adjustment as far as I know, just a zero the scale after it is calibrated.
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- Location
- Western Manitoba
I think what happens is that you place a weight on the scale - then the scale's internal computer says "okay, that is the signal that I get from the weighing transducer at X grains weight" - then sometimes / usually you add a second weight - computer now recognizes signal strength for that weight, and decides that it then knows enough to give you a weight number "within spec". I had a Lyman DPS auto scale and now an RCBS Chargemaster Lite - both required you to press buttons and place weights as a "calibration" sequence - internal computer thing did any necessary adjustments. As you will see on other posts, I also have a "known" weight that I place to see what I get - sort of "old school" confidence builder that the scale's output has value - for me, that "check" reads same on a Hornady beam scale that I still use, as it read on the former Lyman digital, as it reads on this RCBS Chargemaster. I am confident enough that a charge that shows 46.2 grains on the RCBS unit, will also show 46.2 grains on the Hornady beam scale - I am not good enough shooter to know whether that was actually 46.18 grains on one and 46.22 grains on the other - group sizes are no different for me.
Is something that I noticed about various posts - is about what concerns you - I happen to be concerned about where the holes are on the target. Others apparently concerned about the Standard Deviation of their chronograph readings. Some claim concern about the third decimal place grains weight of their powder load. All, no doubt, MIGHT have some bearing on where holes show up on target - but, in the end, for me, is the holes that count, not much else.
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Of course, tiny group size is the ultimate criterion, but it's the other things you mention that lead to this. And you have to let some of us handloaders be obsessive-compulsive.
Seriously though, my main concern in this thread is ensuring that the charge weight indicated on my scale is precise, not, in my opinion, a trivial matter.
