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steel13
HB Life Member
| Joined: | 21 December 2007 |
| Location: | I Live In The Rain, Washington USA |
| Posts: | 204 |
| Photo: | [Download] | | Are you a handloader?: | Yes | | Favorite type of cartridge to load?: | I load everything! |
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Posted: 18 June 2008 04:04 AM |
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So I bought some reloading gear second hand for a very good price and included in the mix was a weight calibration set. I thought,ok, cool, I can double check my scale.
so I put on the 20 gr. little brass weight on the scale, set the scale to 20 grains and it goes all the way to the top of the range. My scale says it weighs 21 grains.
So what do I do now?
I adjusted the little foot to raise and lower the scale but it still says its 21 gr.
Ignorance is bliss, now I wish I had never checked it.
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Oddbod
HB Full Member
| Joined: | 20 January 2008 |
| Location: | United Kingdom |
| Posts: | 64 |
| Photo: | | | Are you a handloader?: | Yes | | Favorite type of cartridge to load?: | rifle |
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Posted: 18 June 2008 10:06 PM |
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Clean the check weights with denatured alcohol or carb cleaner then try again.
Have you tried with any of the other weights?
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steel13
HB Life Member
| Joined: | 21 December 2007 |
| Location: | I Live In The Rain, Washington USA |
| Posts: | 204 |
| Photo: | [Download] | | Are you a handloader?: | Yes | | Favorite type of cartridge to load?: | I load everything! |
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Posted: 18 June 2008 10:11 PM |
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Well the set came with 2 20 grain weights and they both weighed the same and when I add the 10 and the two 20's , it came out to 51 grains.
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ghrit
HB Life Member
| Joined: | 14 April 2006 |
| Location: | Endless Mountains, Pennsylvania USA |
| Posts: | 223 |
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Posted: 18 June 2008 10:42 PM |
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Tt is usually necessary to check the weights at only two points. That will give you a calibration that is straight line if all is right. If you plot two or more check weights on a graph (say 20, 40, 50) the line connecting them should run thru zero. If it doesn't, look further for a problem. On the other hand, if both 20 grain weights don't register the same, question the weights. One ain't what it says.
At 20 grains, reading 21, the error is 5%. With both 20s and the 10 on the pan, the error looks to be 2%. Extrapolating back, at 10 gr, the error is likely around 10%, way too much to ignore. I wouldn't use that scale until you find out what's wrong, unless you are loading BIG ones, in excess of 50 grains and under 100 where my calcs tell me the scale is right on or close enough. (Above that, the error goes heavy, not good.) The error may be linear and at some point will go heavy; you can extrapolate to see where that happens, but extrapolation is risky; it is better to use known weights. If it is linear (and you won't know without some more lighter check weights) you might construct a graph to use in correcting the actual weight vs. measured. Looks to read high in all cases up to 50+ grains, which is arguably safe.
A short batch of theory. One might say that all calibration weights are plus or minus X percent. Assuming a normal distribution of errors, some will be high, some will be low. Thus, using more weights will tend to cancel out the errors of individual weights and you will actually be closer. Meaning if you want 20, then use 4 weights of size 5 and you will be closer than one weight of 20.
Edit to add: Looked it up. Guess I should have done that first. Clean everything with brake cleaner and or alcohol, check that nothing is rubbing, and make sure there is no contamination on the knife edge or bearing plate and that the arms are not bent. Level in both directions counts, eyeball the bearing plate to be sure it is level, not the surface the scale is mounted on. I couldn't tell from the Cabela's data what the max loading is for that device, but my guess is you aren't going to be doing heavies on it. Be safe, make sure the error is reasonable, say less than one percent.
Last edited on 18 June 2008 10:54 PM by ghrit
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Box13
HB Full Member
| Joined: | 21 May 2008 |
| Location: | Beaver Creek, Oregon USA |
| Posts: | 87 |
| Photo: | | | Are you a handloader?: | Yes | | Favorite type of cartridge to load?: | I load everything! |
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Posted: 19 June 2008 04:17 AM |
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| Dont some scales have a calibration screw of some sort on them?.....
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steel13
HB Life Member
| Joined: | 21 December 2007 |
| Location: | I Live In The Rain, Washington USA |
| Posts: | 204 |
| Photo: | [Download] | | Are you a handloader?: | Yes | | Favorite type of cartridge to load?: | I load everything! |
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Posted: 19 June 2008 10:16 AM |
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ghrit wrote: Tt is usually necessary to check the weights at only two points. That will give you a calibration that is straight line if all is right. If you plot two or more check weights on a graph (say 20, 40, 50) the line connecting them should run thru zero. If it doesn't, look further for a problem. On the other hand, if both 20 grain weights don't register the same, question the weights. One ain't what it says.
At 20 grains, reading 21, the error is 5%. With both 20s and the 10 on the pan, the error looks to be 2%. Extrapolating back, at 10 gr, the error is likely around 10%, way too much to ignore. I wouldn't use that scale until you find out what's wrong, unless you are loading BIG ones, in excess of 50 grains and under 100 where my calcs tell me the scale is right on or close enough. (Above that, the error goes heavy, not good.) The error may be linear and at some point will go heavy; you can extrapolate to see where that happens, but extrapolation is risky; it is better to use known weights. If it is linear (and you won't know without some more lighter check weights) you might construct a graph to use in correcting the actual weight vs. measured. Looks to read high in all cases up to 50+ grains, which is arguably safe.
A short batch of theory. One might say that all calibration weights are plus or minus X percent. Assuming a normal distribution of errors, some will be high, some will be low. Thus, using more weights will tend to cancel out the errors of individual weights and you will actually be closer. Meaning if you want 20, then use 4 weights of size 5 and you will be closer than one weight of 20.
Edit to add: Looked it up. Guess I should have done that first. Clean everything with brake cleaner and or alcohol, check that nothing is rubbing, and make sure there is no contamination on the knife edge or bearing plate and that the arms are not bent. Level in both directions counts, eyeball the bearing plate to be sure it is level, not the surface the scale is mounted on. I couldn't tell from the Cabela's data what the max loading is for that device, but my guess is you aren't going to be doing heavies on it. Be safe, make sure the error is reasonable, say less than one percent.
As per your edit,I cleaned it up, readjusted the height footagain and whadaduknow, perfect! It set on "0" and also on whatever weight I put in the pan. Thanks guys.
____________________
halitosis is better than no breath at all!
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Sogmanzulu
HB Full Member
| Joined: | 4 August 2008 |
| Location: | Medford, New York USA |
| Posts: | 28 |
| Photo: | [Download] | | Are you a handloader?: | Yes | | Favorite type of cartridge to load?: | rifle |
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Posted: 1 September 2008 02:04 AM |
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Oddbod,
How are you able to reload in the UK? I was under the impression that you could not even own a firearm...
This is a serious question.
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