Calibration of a 505 scale.
- Thread starter Mtstalker
- Start date
I have an M-5 which has proven itself exceptionally repeatable and linear for the few months I've had it. Nevertheless, I use calibration weights to check it before each session and every time I change the weight of charge I want to use.
I have two reasons: 5% of my concern is that the scale may not, this time, be linear (not seen so far) and 95% of my concern to verify that I have placed the scale's weights in their proper places.
I have two reasons: 5% of my concern is that the scale may not, this time, be linear (not seen so far) and 95% of my concern to verify that I have placed the scale's weights in their proper places.
My 505 was not very good. Upgraded to a Scott Parker tuned 502
The only way to check for accuracy is with known value test weights. You need to make sure the scale is clean and free of any oils or dust. I use Stoddard solvent and finish cleaning with hot soapy water and a final rinse with alcohol. Blow all the parts dry with air and then assemble it. You should check it close to full capacity and at close to minimum capacity. Then check near the weights you most often deal with. If it is off more than .1 grain then it needs to be calibrated.
There are two main methods of calibration;
1. adjustable balance
and
2. weight balance.
With the adjustable balance the beam will have a threaded stud at one end with a lock nut or a nut and a jam nut. These are adjusted to set the balance at full scale. it is then checked at the other points to ensure the balance is linear.
With a weight balance scale the pan platform has shot in it - sometimes lead and some times other materials. You add or subtract shot or pieces of shot to zero at full scale. The balance is then tested at other weights to ensure the balance is linear.
Things that will affect sensitivity and repeatability are the knife edges and the bearing points and the sides of the stand in which the bearings are held. No rubbing anywhere! All parts should be clean and free of any oil.
There are two main methods of calibration;
1. adjustable balance
and
2. weight balance.
With the adjustable balance the beam will have a threaded stud at one end with a lock nut or a nut and a jam nut. These are adjusted to set the balance at full scale. it is then checked at the other points to ensure the balance is linear.
With a weight balance scale the pan platform has shot in it - sometimes lead and some times other materials. You add or subtract shot or pieces of shot to zero at full scale. The balance is then tested at other weights to ensure the balance is linear.
Things that will affect sensitivity and repeatability are the knife edges and the bearing points and the sides of the stand in which the bearings are held. No rubbing anywhere! All parts should be clean and free of any oil.
When you got your check weights was your 505 accurate or did you need to adjust it ?
I've just got a Chargemaster and now I've got doubts about my 505 accuracy. Never thought it would matter in the way I work up my loads from below published max's and use a crony too, but of late my historical loads have not produced the same accuracy using the 505 that I've only ever used. For a 223 load the 505 was throwing nearly a full grain more than the CM. The check weights that come with a CM are far too heavy for the 505 and I think I'll just make some using the CM to check against and then fine tune my data to match the CM scales.
Maybe my poor old 505 needs a good clean but I try to look after it, it's only 40 years old.
When you got your check weights was your 505 accurate or did you need to adjust it ?
I've just got a Chargemaster and now I've got doubts about my 505 accuracy. Never thought it would matter in the way I work up my loads from below published max's and use a crony too, but of late my historical loads have not produced the same accuracy using the 505 that I've only ever used. For a 223 load the 505 was throwing nearly a full grain more than the CM. The check weights that come with a CM are far too heavy for the 505 and I think I'll just make some using the CM to check against and then fine tune my data to match the CM scales.
Maybe my poor old 505 needs a good clean but I try to look after it, it's only 40 years old.
Assuming you zero your 505 before each use I can't explain why it would be off by as much as 1 gr. Maybe after so long, parts wear out over time ?
I never had to adjust my 505, it was dead on the first time I used the check weight to the last time I used it. I only used it for a few years before getting the CM.
I don't remember how much I paid for the check weights, but I'm glad I got them. I use them on my CM almost every time I use it, just for a piece of mind.
The RCBS check weights I have come with....
1 x 0.5 gr
1 x 1.0 gr
2 x 2.0 gr
1 x 5.0 gr
2 x 10.0 gr
1 x 20.0 gr
They're worth every penny.
Brians356
Gold $$ Contributor
If you search the forum, Scott Parker has said the 5-0-5 has a fatal flaw, in that the middle poise doesn't settle repeatably in the beam's index notches. I've switch to an M5, and check weights to keep it honest.
http://forum.accurateshooter.com/threads/on-beam-scales-part-two.3906350/#post-36803364
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http://forum.accurateshooter.com/threads/on-beam-scales-part-two.3906350/#post-36803364
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Ahhh, that might be a clue to what might be happening, Thanks, I'll check that out.
Well I had the chance today to shoot my 223 and prove a point with my historical loads based on my old but now suspect 505 but weighed with the CM only. 3 of 5 went through one hole @ 100 yds so in my mind the 505 needs some work to be trusted again.
Well I had the chance today to shoot my 223 and prove a point with my historical loads based on my old but now suspect 505 but weighed with the CM only. 3 of 5 went through one hole @ 100 yds so in my mind the 505 needs some work to be trusted again.
I can supply you with a great scale.
Scott Parker
Thank you Scott, I am aware of your great work but my needs are quite modest and for the time being I will clean up the balance beam of my 40 yr old 505, trim the zero and see how things progress from there. Knowing now the 505 is problematic is in some way a great relief as I'd been doubting all manner of things including my shooting ability. <scared>
At least I have this new CM as a x reference now and if I can get the 505 and the CM to agree to 2/10ths or better I'll be happy.
Thanks to all in/for this thread and the info it offers.
I'm in need. Have a rcbs and a ohaus.
Do you have a webpage put up yet? So we could get an idea of price range etc..
Thanks,
Shawn
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