How to Zero or Calibrate a Scale 

In the first part of this video, you are actually talking about zeroing the scale. Calibration is setting your scale's output to match a known weight. That is what the check weights are for. And I believe that the 250 check weight that you refer to is to add capacity to the scale; you place that weight on the hook near the pointer end of the scale. This will increase the capacity of the scale by some amount that is stated in the manual.

These are old scales. They haven't been made for decades. The lead shot oxidizes and this changes its weight. I have found that I have to add a little bit of lead shot to re-calibrate. Try taking a piece of lead birdshot and crushing it with pliers. Then use scissors to cut off small pieces to ad to the scale pan hanger to get back to zero. Yes, use check weights to be accurate.

Did you read the directions that came with the scale? Calibrating is done with the adjustment screw at the base.The weighted pan is a factory calibration and should never be changed!!!

Thank you so much for this video. I've just bought an old 10-10 scale, and this helps a bunch :).

Yes. I see i missed an important piece of information in my video. I will go back and correct this asap. 1. The scale needs to be level 2. There is the adjustment screw 3. Added wt must be non magnetic

After all these years, I never knew that 😊

It is not as check weight. it is the weight that you put on the scale hook to make you go from 510 to 1010. this scale does not come with check weight. Only a weight to increase scale capacity.

Thank you for showing us how NOT to calibrate a 10-10 scale! Calibrating is done on the poise of the 10-10 by adding or removing material. usually it is fine the way it is. But IF you have to calibrate it, make sure the scale is leveled 100%, knives and pivots are clean. The knives should not have any burrs! Then move the poise in increments of 50gn and write down what you read. Go all the way up to 500gn. If done, you have an idea what your scale really shows and where it begins to show an offset. Usually I move the poise to 300gn and add or remove weight at the back of the poise to get it leveled at 300gn. This will reduce the error significantly and your 10-10 is tuned. Now repeat the steps and check in 50gn increments and enjoy a calibrated 10-10

You don't even mention the adjustment screw. It is that part where the check weight sits. Screwing that down will raise the front of the scale so you really don't need to add weight to the pan if it is already close. Just turn that knurled knob for fine adjustment.

That’s a load of crap