RCBS Scale

[454bore]

Ran into something weird with my RCBS 10-10 scale. I had bought it some time ago and exchanged it several times with RCBS for a replacement due to the scale not weighing my RCBS check weights accurately (off as much as 2 to 3 grains). According to my RCBS Chargemaster the checkweights all weigh as labeled.

With the 10-10 when I dump a charge in below the target weight and then trickle it up - it is showing accurate (as double checked in my Chargemaster).

Any ideas why the scale would not show an accurate reading the checkweights yet when weighing a charge it does?

FYI - the scale is sitting on a leveled granite counter top.

Thanks

 

[in2deep]

When using a checkweight you say it's off but is it off the same each time and repeatedly showing the same spread or does it weigh differently each time you re-weigh it?

My 1010 and Green Machine disagree with each other by .2 but it's always the same and consistent and I just compensate. The 1010 actually repeats better (to the kernel) than the Green Machine and I trust it lot's more to repeat a charge. The Green Machine says that it can throw charges that are 2/10 apart but still read the same (1/10 high or 1/10th low) whereas a good beam shows exactly the same weight each time since the mechanics of gravity are pretty simple compared to the electrical scale that extrapolates a reading and displays it in a numerical LED.

 

[454bore]

There is no consistency in how far it is off when using the check weights.

 

[gambleone]

How much do your check weights weigh?

 

[454bore]

They are the RCBS Check Weights. The set includes 0.5gr, 1.0 gr, 2.0 gr, 5.0 gr, 10.0 gr, 20.0 gr, 50.0 gr, 100.0 gr, and 200.0 gr weights.

 

[gambleone]

So your saying the wt is off with every one of these test wts?

 

[BoydAllen]

Over the years, I had become disillusioned with my 10-10. Then, after reading about "tuning" balance reloading scales, i decided to give it a try. I figured that, worst case, I would have the fellow that does this commercially straighten out my mess, so with some trepidation, I gave it a try. It worked. My scale is a reliable instrument. I would say again, but it wasn't any great shakes in the first place.

The first thing that I would suggest is to use one of those cheap diamond hones (Mine says that it is coarse, but it has worn some.) to sharpen the knife edges to the point that you don't see any shiny spots on the edges, when looking directly at them, with a little magnification. (Turn the scale beam so that its bottom is facing you.)

The second thing that I would do is to remove the agates and clean them and the cavities that they sit in with alcohol and Q tips, before reassembling.

Then, I would set about adjusting the tuning weights that are contained in the powder pan holder to the point that when the scale is set at zero, that the marks are in perfect alignment, AND the frame of the scale is level. I use a torpedo level. I think that that is good enough for this purpose.

If the counter weight is too heavy, I take out a piece of shot, reassemble the pan holder, and cut small pieces of plastic and put them in the pan until the balance marks are perfectly aligned (with the body of the scale level). Then I put the pieces of plastic in with the shot. and recheck the scale.

If you like, try all of this, and then if you are ambitious, you can start to think about whether the movable weight needs a tuneup.