Reloading calibration weights for scales

[Army-medic]

Just giving you a heads up that they sell pharmaceutical 'apothecary' weights measured in grains on that popular auction site.

I had a set for £10 as opposed to nearly £50 for a dedicated, purpose-specific item.

[Turnup]

I too thought that would be a good way to go. Unfortunately I have found that they do not agree with each other. Either age or indifferent original calibration makes them useless. Your luck may be better.

[angrybear]

I use a balance scale so there's nothing to calibrate

[stillair1]

I use a balance scale so there's nothing to calibrate

Still useful though just to check what you think you've set it to is right. Once the check weights have been verified that is.

[Army-medic]

I use a balance scale so there's nothing to calibrate

I highly doubt balance scales remain 100% accurate forever. I think it's a sensible option to check that the measurements are correct. But if you don't need them; great.

[angrybear]

I highly doubt balance scales remain 100% accurate forever. I think it's a sensible option to check that the measurements are correct. But if you don't need them; great.

Yes, they should, because there is no mechanism to go wrong, springs to stretch, etc.
A machined weight a certain distance along a bar requires a specific predetermined weight to balance it, about as basic as it gets.

Biennial station "weights & measures testing" was another task I have suffered the "joy" of carrying out while in the RAF.

[Turnup]

I highly doubt balance scales remain 100% accurate forever. I think it's a sensible option to check that the measurements are correct. But if you don't need them; great.

Yes, they should, because there is no mechanism to go wrong, springs to stretch, etc.
A machined weight a certain distance along a bar requires a specific predetermined weight to balance it, about as basic as it gets.

Biennial station "weights & measures testing" was another task I have suffered the "joy" of carrying out while in the RAF.

While I agree that there will be little change over time (I can think of some but they are small by comparison to the level of accuracy needed for reloading), they were never 100% accurate in the first place!. Calibration can be done in two ways:

1) Adjust the instrument to agree with known standard values. (and very time consuming that can be when calibrating over the entire range of an instrument)

2) Where the instrument has no adjustment, record the error when measuring known values, plot a graph of multiple points, and thus have a range of correction values for that instrument.

Reloading scales will have errors in the actual weights of the sliders, errors in the measurement of the slider position, errors in the bearings, all of which can be calibrated by method 2).

That said, no-one is particularly interested in the exact weight of powder for reloading (within reason) - repeatability is the key to making that magic load time and again and I don't much care if my scales indicate 2.9 grains when the actual weight is 2.84 grains, provided that they do so consistently.

[1066]

I use a balance scale so there's nothing to calibrate

I'm really not clear what you mean by a balance scale. Any chance of a link to an image of what you are talking about?

[angrybear]

I'm really not clear what you mean by a balance scale. Any chance of a link to an image of what you are talking about?

RCBS 5-0-2 just google it.

A beam that balances once a weight is pre-set at one end & powder of the exact same weight added at the other end

[1066]

Ah! We're talking just a standard reloading scale then. - Always a good idea to have a set of grain check weights and use them regularly, especially if, your developing loads or working towards the top end of loads.

Even basic beam scales can sometimes give false readings - friction in the knife edge bearings, friction in the knife edge pivot points, agate bearing misaligned, friction in the panhanger stirrup bearing, loose damper blade etc. etc.