My RCBS 10-10 scales is not reading accurately

[Vacek]

I picked up a used 10-10 a couple of weeks ago and have just set it up. I leveled it and it initially wouldn't zero regardless of level adjustment. I removed one of the larger lead BB's and added back 2 and a fraction of #8 lead shot to get it to zero after a slight level adjustment..

I have a set of Class S weights (I used to run a lab so I understand this stuff) and placed a 2 gram weight on the 10-10. 2 grams are equal to 30.85 grains. My reading was 32.5 grains which is a very significant difference. A 1 gram weight also read high on the 10-10.

I have two 30+ year old Redding Scales, a digital scale (reads to 0.001 gram) as well as several others that read accurately. The digital scale (0.001 gm resolution) read the 2 gram weight at 30.853 grains. I also never had this kind of accuracy issue with the Lee Scale although I didn't care for it .... it was accurate.

Any ideas what may be going on with the 10-10? By reading this forum it seems to be the gold standard but in this case it is not.

 

[rcmodel]

Take a cotton Q-Tip and rubbing alcohol to the v-blocks and beam knife edges.

Make sure the magnetic dampener plate on the beam isn't bent and rubbing on the base.


BTW: I wouldn't have started adding & changing the factory balance lead shot that soon.

Maybe you bought a used scale with the wrong pan on it!

rc

 

[burrhead]

Did you check the knives and v blocks for chips, grunge, etc.?

RC types faster than I do.

 

[Vacek]

I will do the cleaning tomorrow and update. I can replace the Lead BB with the #8 shot if needed. The cleaning of the V and edges are probably the issue as the balance seem a little insensitive and that would explain it. The magnetic damper seems fine.

I downloaded the instructions from RCBS and it is the correct pan.

 

[LiveLife]

I bought both of my Ohaus 10-10 scales used (second one was new old stock) and had similar issue of scale not maintaining zero. Good cleaning of agate bearings and posts solved the problem.

I found the repeatable zero resulted from the knife edges pivoting on the free floating agate bearings. Can you inspect the beam/knife edges to make sure they are not bent and at 90 degrees? FYI, I do the following to clean/tune the scale.

- Remove the bearing covers with a Phillips screwdriver (see pictures below)
- Make sure the posts the agate bearings free float on are clean
- Clean the agate bearings, especially the "V" notches
- Re-install the covers
- Clean the knife edges
- Level the bench surface using a bubble level at 90 degrees
- Turn HVAC/vent off and close the window/door to the room as any ambient air movement will affect scale reading/zero
- Place the powder pan on the pan support
- Set both large and micrometer poises to zero
- Lock the micrometer poise with the nylon bolt
- Adjust the leveling foot so the pointer is at the zero line

I have a set of Class S weights (I used to run a lab so I understand this stuff)

Once zeroed, check accuracy using check weights (don't forget to unlock the micrometer poise nylon bolt). My Ohaus 10-10 scales are sensitive to one piece of 1/4"x1/4" 20 lb copy/printer paper (~.05+ gr) and will consistently verify 10 mg Ohaus class 6 check weight (~.154 gr). If you still have zeroing issues, you may need to give RCBS customer service a call.

Ohaus 10-10 agate bearing

RCBS 5-0-5 agate bearing

 

[Kp321]

The suggestion was made that you might have gotten the wrong pan/hanger with the used balance. Although all 10-10 pan hangers look alike, each is calibrated to its individual beam.

 

[1066]

The suggestion was made that you might have gotten the wrong pan/hanger with the used balance. Although all 10-10 pan hangers look alike, each is calibrated to its individual beam.

Quite true.
Here's a short video I made some time ago about the 10/10 scale and how to adjust the tare weights when using a different pan.

https://www.youtube.com/watch?v=HOKJxe0FUTk

 

[DaveInFloweryBranchGA]

One thing you should be aware of is newer RCBS scales are now made in Mexico using a different manufacturing process designed to cut costs and are not the scales they used to be. Unfortunately, the cost cutting affected both the accuracy and tuneability of the scale. Parts that were once machined are now stamped, etc.

Look on the bottom of your scale and make sure where it was made before proceeding. If it's made in Mexico, it may not be worth your time investment.

 

[1066]

Look on the bottom of your scale and make sure where it was made before proceeding. If it's made in Mexico, it may not be worth your time investment.

Even the new ones have something like Ohaus NJ cast into the base when in fact they are made in China. Some of the new ones have a small paper sticker saying Made in China. The bottom of the cardboard box tells you where it was actually made (Mexico or China)

 

[gamestalker]

Also make have sure you don't have any electric motors near, florecent lighting, magnets, electric cords or anything that can create a field near by. Also ceiling fans, AC/heating registers moving the air around.

I have an ancient 5-10 that gave me fits when I first got it, until I realized it was my electric drill that was sitting too close. Now that I've figured out what causes these little hiccups, I have had no problems and trust my scale 100%.

GS

 

[vaalpens]

- Remove the bearing covers with a Phillips screwdriver (see pictures below)
- Make sure the posts the agate bearings free float on are clean
- Clean the agate bearings, especially the "V" notches
- Re-install the covers

bds, thanks for the detailed write up. One question I had when I cleaned my scale was the direction the agate bearings should go in. If you look at them it seems that the top flat edges are different width. Does it makes any difference if the thinner one is facing to the front or back? I just put both in the same direction, but I'm not sure if it makes a difference or not.

 

[TexasDon]

Nothing more to be said, seems like all the info you got is great and should work.
If not, email/call RCBS and they should replace it....

The 10-10 is a great scale and something can go wrong with any of them.
I've had to clean mine a few times in many years from dust etc.

May have missed it mentioned above, but make sure the table it's on is level.
I made a special adjustable table for my scales that sits along side of one of my benches. That way there is no vibration from presses or anything else.
And slight breezes will cause them to fluctuate, but it sounds like you understand them since you have Lab experience.

Have fun and be safe.
TxDon

 

[LiveLife]

One question I had when I cleaned my scale was the direction the agate bearings should go in. If you look at them it seems that the top flat edges are different width. Does it makes any difference if the thinner one is facing to the front or back? I just put both in the same direction, but I'm not sure if it makes a difference or not.

The agate bearings need to "free float" on the posts and if the "V" notch cuts are not even (see picture below), mismatched orientation of the bearings may cause the knife edges to bind to not give you consistent zero/readings. I would definitely put the same "width" bearings in the same direction as the mismatched "V" notches may not align with the knife edges which are 90 degrees with the beam. The knife edges need to sit on the bottom of the "V" notches and pivot with the agate bearing "free floating" on the posts to give you reliable/repeatable performance.

 

[Vacek]

The cleanup solved the problem. Thanks to all

 

[LiveLife]

Awesome!

I love happy endings.

 

[rcmodel]

Did you put the factory calibration shot back in the pan hanger where it came from??

DoDat if you didn't!!!

rc

 

[Vacek]

Well, I did put things back together and it zeroed better. I thought the problem was solved but I continue to get poor precision on the readings. I contacted RCBS and am going to send it in for repair and recalibration.

 

[Matt Dillon]

Turn the scale over and inspect for any pieces of metal or paper clips stuck to the magnets. Mine had some paper clicks stuck there , and once I removed them, I was able to get very consistent readings.

 

[Vacek]

That was an interesting thought but nothing attached to the magnets. I am going to box it up and send it in.

 

[gamestalker]

Things sticking to the magnets, forgot about that one, it's happened to me a time or two.

But at any rate, RCBS will make things right I'm sure.

GS

 

[sage5907]

I never use my 10-10 scale when the central heating & air conditioning unit is running because just the movement of air in the room can affect the readings.

 

[TexasDon]

sage5907

I never use my 10-10 scale when the central heating & air conditioning unit is running because just the movement of air in the room can affect the readings.
__________________
sage

I use to have an OLD Redding balance scale that would "move" if you breathed on it lightly.
It drove me Krazy..!!!

TxD