RCBS 10-10 scale


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Kestral
January 18, 2009, 12:00 PM
Using a RCBS 10-10 scale,I trickle in the final grains of powder till the dampened beam is dead level.If I then gently tap the beam,it registers 1/8" to 3/16" over the mark.Could someone with more experience than me tell me which is the correct reading, or what am I doing wrong to get a double reading like this.Many thanks Kestral

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243winxb
January 18, 2009, 12:09 PM
http://www.thehighroad.org/showthread.php?t=411418 this may helphttp://www.thehighroad.org/showthread.php?t=411578&highlight=balance+beam+scale Looks like you been having way to many problems with that scale, i would buy another one.

RidgwayCO
January 18, 2009, 12:23 PM
Do you have a set of check weights? I've found them invaluable for checking the accuracy of my scales. Pretty cheap insurance.

http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=212586

They would tell you which weighing method (tapping vs. no tapping) you should be using.

Galil5.56
January 18, 2009, 12:30 PM
IMO, it's because the main poise tab is rectangular in shape, going into a "V" notch. Almost imperceptible movement can throw off actual measurement by +/- .3 grain in my experience, and I've never seen an Ohaus beam-and-poise scale that did not do this. I usually witness it when the pan is lifted, and the beam allowed to rest, even when done very gently. I'm sure a little bit of binding of the knife edges in the floating agate bearings from side-to-side movement contributes some as well, even when spotlessly clean.

I mentioned this "problem" in a recent analog vs digital thread, and it goes to show that no scale is perfect.

http://www.thehighroad.org/showpost.php?p=5232525&postcount=17

Kestral
January 18, 2009, 01:24 PM
Thanks for your patience,I`d forgotten I`d posted on this subject before.Its an ongoing problem,so I will scrap it & find a better one. As I note you are a retired dealer,so could I ask which quality scale would you recomend.? Im not to bothered on cost,but I do need reliability more than anything else.Thanks for your help.Kestral

243winxb
January 18, 2009, 03:14 PM
Kestral, at one time Ohaus made most of the scales available under different company names. I dont know if thats true today. Any make should work well. http://www.midwayusa.com/ebrowse.exe/browse?TabID=1&Categoryid=19934&categorystring=9315***731***9211*** I am using a very old Bonanza Model M, a very basic scale.

243winxb
January 18, 2009, 03:45 PM
hysteresis http://www.thehighroad.org/showpost.php?p=5138715&postcount=4 Looks like others have run into the same problem your having. First i have hear of it. I am only on my second scale, never had a problem so far. Something i founds>> What affects both accuracy and precision is beam/bearing friction. We MUST keep the pivot knives and bearing grooves clean - I use an alcohol dipped toothpick to clean the bearings and Q-tips for the knives. AND don't let the ends of the knives rub against the stops on each end of the bearing holders - this one is hidden and seems to drive some folks up the walls from time to time!

243winxb
January 18, 2009, 04:10 PM
http://www.benchrest.com/forums/showpost.php?p=470811&postcount=11 More on the RCBS I have learned to tune up my scale (a RCBS 10-10). I removed the agate pieces that the beam knife edges rest on and cleaned them and the metal that touches them with alcohol and Q tips. After replacing them, I leveled the base of the scale, removed the pan holder, disassembled it, removed one of the spherical weights, reassembled it, and assembled the scale, with the weight and adjustment set to 0 and the pan in place. I then started adding small pieces of plastic (snipped from a spare shirt collar stay) to the scale pan, until an exact zero was reached (using the mirror technique explained above). I then took the pan holder apart and added the plastic pieces to the collection of spherical weights, and reassembled the pan holder and the scale. It was right back on zero. Next I checked it against some check weights, and it came out right on the money. I keep the dust cover on the scale, except when it is being used, and store it in its original cardboard box, in a drawer. I might add that I have tuned up three scales of the same make and model that had previously had to have their left ends jacked up well past level to zero the scale. I think that this puts the Vs in the agates in misalignment with the beam knife edges, resulting is poor performance. They all worked much better after the tune-up.

ranger335v
January 18, 2009, 06:34 PM
"...don't let the ends of the knives rub against the stops on each end of the bearing holders "

There's your problem. Clean the knives and both agate V bearings, then center the knife bar between the bearing retainer clips. All will be well.

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