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Old January 13, 2013, 01:59 PM   #1
S_Constitutionist
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RCBS 10-10 inconsistent zero?

After using a cheap digital scale for a number of years, I decided I wanted to upgrade to a more trust worthy scale. All of my loads have been fine, but the Frankford digital just didnt afford much piece of mind.

I purchased a new RCBS 10-10 from Amazon a few weeks ago as well as a set of Lyman standard check weights (.5gr, 1gr, 2gr, 5gr, 10 gr, and 20gr). Following the directions, I was able to zero the scale and check the test weights. Each test weight was within .1gr on my digital scale, but varied as much as .3-.4gr on my 10-10. I check zero again, and find that it has drifted .1-.2gr. Rezero and check again, this time the weights are spot on. To double check, I tested a known powder drop (4.0 grains of tite group, my go to 9mm load). I was quite surprised when the 10-10 read at 4.3. So, I check zero and AGAIN the RCBS had to be adjusted to achieve zero.

Does anyone have any idea whats going on here? I know this is difficult to diagnose at a distance, but im confused about what could possibly be causing this. The scale hasnt been bumped or moved. I've owned 2 other RCBS scales (both 5-0-5's) that I had to return for similar issues. Is RCBS just a poor quality brand?

For the money I am pretty disappointed. I just wanted to see if I was doing something wrong before returning it.
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Old January 13, 2013, 03:12 PM   #2
Kevin Rohrer
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I was curious about my electronic RCBS scale, so I bought a 10-10, assuming it was accurate. When there was a .4gr inconsistency between the two measures, I bought a set of check weights. It turns out that the electronic scale is fine, but the 10-10 registering low. Crazy.
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Old January 13, 2013, 04:46 PM   #3
Lost Sheep
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Thanks for asking our advice

Surprizing to find RCBS scales that are inaccurate. By the way, Ohaus makes the scales, as well as those sold bearing the paint and nameplate of Dillon and almost all others except Lee.

If the fulcrum (knife-edge and jewel) points are full of dust, gunk or are cracked, bent or worn you will get bad readings. Cleaning works for dust and gunk. Replacing the parts (that means sending the scale back) works for the rest.

You mentioned zeroing the scale, so I will assume you are doing everything else right But for one exception: While the scale is still settling, watch the pointer as it swings up and down. Is the movement a perfect, decaying sinusoid? Or does it "catch" and jerk and vary in speed? Does it swing up to a point, then down to a point then up again to a point not quite as high as the first time and then down to a point not quite as low as the first time and repeat this decaying amplitude until the pointer is still? (Similar to the decay you observe if you let a golf ball on a hard surface until is comes to rest)

Sometimes the fulcrum binds just from the beam not being centered in the jewel bearings. If either end of the knife-edge touches the end of the cradle your beam will never work right, so make sure it is centered. Likewise if the copper plate that provides magnetic damping rubs on anything.

Other than binding of the beam (at the fulcrum or other point), there is virtually nothing that can prevent repeated measurements from being precisely the same every time. Balance is balance.

If your sliding weights (on the 10-10, I include the threaded weight, too) are the right weight and the markings in the right positions, there is nothing that can prevent measurements from being correct (as long as you are close to the surface of the Earth and stationary). Gravity is gravity and doesn't change much.

1) The scale must be on a stable surface. Put it on a concrete slab floor if you have to.

2) Make sure there is NO air movement. That blows (pun intended) all reasons out of the water. If you have to, put a cardboard box over the whole thing and watch it through a small (1" maybe) hole and a flashlight.

3) Make sure your beam is not touching anything (binding) and is completely free in its movements and that those movements are up/down only, not any side to side or lengthways. (Gently wiggle the beam to settle it into its lowest position.)

4) Make sure your bearings and knife-edge are clean and in good condition

5) Test your beam by watching it oscillate and settle down. Then do it again to verify that the oscillations decay smoothly and that it settles in the same place.

Good Luck

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Old January 13, 2013, 06:15 PM   #4
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Thank you very much for your detailed reply.

The scale is brand new, but I have NOT cleaned the parts. I will try that first.

The pointer is semi-sinusoidal, with occasional "catching" as you call it during decay. This does not happen all the time which could be causing the inconsistency. Makes sense to me.

I have already turned off the heater and all fans in the house, but I'll try the box trick if there are still issues. There is no binding or any contact with the dampner or pointer.

I'll post back with results. Thanks again!
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Old January 13, 2013, 06:42 PM   #5
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4) Make sure your bearings and knife-edge are clean and in good condition

Make sure you haven't moved the beam forward or backward enough to let the axle rub against the agate V brearing retainer clips. (Mostly likely the problem.)

Clean the bottom of the V bearings with a sharp toothpick to make sure there's no dust or grit in there, then clean the knife edges with a tissue. DO NOT oil the bearings or knives and DO NOT attempt to secure the V bearings so they can't 'float' into perfect alignment.

Insure there is no spider web in the slot where the copper vane on the left beam end goes.
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Old January 13, 2013, 07:31 PM   #6
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RCBS beam scales are excellent. I have used the predecessor to the 505 for about 20 years with no problems. It has measured 10's of thousands of charges. I have never checked zero on it with a weight set. I zeroed the beam 20 years ago and it still returns to Zero. I dont really care if a scale is accurate as long as it is consistent.
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Old January 13, 2013, 07:58 PM   #7
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I have tried all of the aforementioned tips and spent a good deal of time cleaning the bearings and knife edge of the beam. I am not sure how to check that it is perfectly in the middle; it seems to fall into only one position.

I had to re-zero. 4gr check weight ((2)gr): 4.3gr

Pulled the check weights out and tested them on my digital: 4.0gr

Looking back at the 10-10, the zero needed to be adjusted again.

Before re-zeroing, I tried lightly bumping the beam to get the pointer to go through another full range of motion. This worked once, causing the pointer to return to true zero. I added the same check weights: 4.1gr. Pulling them off, no longer at zero. I then did the bump trick 5 or 6 more times, and it still would not return to zero.

Im not sure if I should exchange it with RCBS or simply get a refund through Amazon... I was told that the 10-10 was about as good as it gets before going to an analytical (which I simply cannot afford). Perhaps I'll try another brand - 3 bad RCBS/Ohaus scales (one I do believe was damaged) is simply too many. It seems to be the older scales (15-20 years ago) that get such high praise.

Thank you all for your help.
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Old January 13, 2013, 08:09 PM   #8
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With my Ohaus made Dillon branded Eliminator, I was able to get over the early speedbumps by ensuring that the hanging device that the removable pan is placed upon was rotated to a spot that welcomed the pan to sit in a very repeatable manner.

Everything else mentioned is also quite valid. These scales...they amaze me. The sensitivity is unreal for a low-dollar piece of consumer equipment.

The early struggles I had seemed like a downer at the time, but it was just another way to point out vividly that the scale was SO sensitive (accurate) that it would magnify any mistake that I was making.

It's certainly possible that there's something defective in your 10-10 but I can honestly tell you that if it's not actually defective or broken...you do have one heckuva fine tool there. What you've read is true. The 10-10 is a gem.

Please make sure you update this thread no matter how it gets resolved. These little conversations often help countless folks in the future even if they never need to post in the thread.

Good luck!
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Old January 13, 2013, 08:13 PM   #9
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It's a mechanical scale. There has to be something wrong which can be seen.

These things don't have strain gauges, batteries, etc. They are as reliable as gravity, if they are clean.

What about the knife edges? Nice and sharp on both sides? All it takes is a burr and it won't pivot correctly.

Agates aren't cracked? They should be "floating" in their pockets.

Copper vane isn't bent and touching? (I think you already said nothing is touching, but this kind of rides "behind" everything else.)

If all the parts are OK, it has to work. Don't give up on it...
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Old January 13, 2013, 08:14 PM   #10
reynolds357
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Try using heavy test weights similar to actual powder charge weights.
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Old January 13, 2013, 08:16 PM   #11
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I would ask for an exchange. I have used a 10-10 for 24+ years and have never seen that problem unless I bumped the scale and cockeyed the pivot. It only needs rezero after moving to a different location/surface.

I have checked it many times with a check weight and other known weights. Once zeroed it weighs the item consistently time after time. An excellent scale with very smooth swings to settle in on the balance.

Once I thought it was haywire because it would not zero. Turned out I had removed the little plastic screw on the tenths drum weight! Put it back on the arm and zeroed perfectly.

Yours sounds like a manufacturing defect or shipment damage (perhaps the pivot bearings?).
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Old January 13, 2013, 08:58 PM   #12
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One thing I haven't seen mentioned. Is whatever it is sitting on level in both directions?
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Old January 13, 2013, 09:05 PM   #13
S_Constitutionist
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Alright you win! I'll unpack it and try some more. Nothing else to do on a Sunday night with no football on... Also amazing how much free time you have when you quit drinking

Yes, I've tried it on multiple surfaces that all checked out with a bubble level.

As of yet, I only reload handgun calibers (9mm and .45) so between 4 and 5.5gr is where I NEED the scale to work.

I'll let you know how it goes. I may be able to make a video on upload it to youtube (never done that before) to show you.

Thank you folks, again.

Last edited by S_Constitutionist; January 13, 2013 at 09:12 PM.
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Old January 13, 2013, 09:17 PM   #14
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I blow off my scale each time I use it with canned air to remove any grit or dust from the pivots and beam. When not actually in use, I cover the scale with a folded sheet of paper to prevent any dust from settling on it. If the beam gets bumped or jiggled during use, I rezero immediately.
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Old January 13, 2013, 09:23 PM   #15
S_Constitutionist
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Did I find the culprit?

The bearings (not sure of the correct term. Agate?) are not located symmetrically. While the one nearest the user is sitting flush in its recess, the opposite bearing is not.




Unfortunately I dont have a phillips both small and narrow enough to reach the set screw from the access hole on the back side. Should these be torqued down or allowed to float a bit, as one user mentioned? Mine are quite tight.
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Old January 13, 2013, 09:39 PM   #16
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The agates are supposed to float around in their recesses. I believe it's OK for the metal cover plates to be tight.

I can't quite tell from your pictures, but if the agates aren't level, the knife edges can't rest against them correctly.

There may be some dirt under one of the agates. (? unlikely with a new scale, but stuff happens...)

You should be able to remove the metal covers, check under the agates, then reassemble everything.
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Old January 13, 2013, 10:18 PM   #17
S_Constitutionist
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Oh, I see now. I thought the cover was part of the agate.

I am not able to clean them tonight.

I tried again by centering the pivot between the agate covers (y axis, looking down) thinking that perhaps it was binding on one of the covers. This worked a few times, but again inconsistency reared its ugly head. I was able weigh the included 250gr weight perfectly and allow it zero on its own twice, and then began getting readings of 250.4, 250.5, and failing to zero.

The knife edges are a perfect machined edge. The paint was stripped where it was machined - is this the case on yours as well? Perhaps a "refurbished" unit?

I just cant tell whats what
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Old January 13, 2013, 10:30 PM   #18
Lost Sheep
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Quote:
Originally Posted by S_Constitutionist
I tried again by centering the pivot between the agate covers (y axis, looking down) thinking that perhaps it was binding on one of the covers. This worked a few times, but again inconsistency reared its ugly head.
That's a clue. I don't know what it means, but it is definitely a major clue.

Take that information to RCBS. Their Customer Service will serve you well.

Lost Sheep
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Old January 14, 2013, 12:23 AM   #19
dmazur
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Quote:
The bearings (not sure of the correct term. Agate?) are not located symmetrically. While the one nearest the user is sitting flush in its recess, the opposite bearing is not.
I think this is most likely the problem. The agates have to be level (with respect to the scale body) for the beam knife edges to be supported properly.

If one is higher than the other, it will definitely make the assembly work worse than it was designed.

It could be as simple as cleaning / reassembly. (Once you get the right tools.)

But if it is a genuine manufacturing error, RCBS owes you a new scale.
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Old January 16, 2013, 04:39 AM   #20
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The knife edges on my 10-10 are ground bright bare metal as well. No problem, normal.

I would call RCBS and arrange for replacement. Yours is not working as it should.
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Old January 16, 2013, 12:34 PM   #21
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Any updates from the OP?
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Old January 16, 2013, 02:48 PM   #22
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I've seen a couple of folks mentioned checking the copper eddy current damper plate (aluminum on my Ohaus, but everyone is saying copper, and I don't have an RCBS version handy to check). This plate swings through a slot between two opposite permanent magnet poles. That causes the moving plate to cut through the magnetic lines of force, generating eddy currents by induction. The solid metal plate then also shorts out that induced current, loading the "generator" down, making it drag. This is why it damps out the beam swing much more quickly than would be the case if it were simply a free balance.

If that plate were dirty or bent, as mentioned previously, it would rub the magnets and cause the observed irregularity. However, I find it much more common that a splinter of steel wool, a staple, or some iron filing dust has been caught by the magnets and drags on the damper plate, but does not come out with it.

Lift out the beam and shine a light down between the magnets to see if anything is there. If so, try cleaning it away by sliding some tape into the slot and up against the magnet to grab the errant steel or iron. Do this on both sides until it looks clear.
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Old January 17, 2013, 02:52 PM   #23
S_Constitutionist
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Hi folks,

I am waiting on the phone with RCBS to arrange an exchange. The tech had me perform a few tests and they agreed that something is in fact wrong with it.

Thank you all for the help.

edit: No RMA required or anything. That was a LOT of waiting on hold to just be told to pop it in the mail. Oh well.

Last edited by S_Constitutionist; January 17, 2013 at 03:31 PM.
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Old January 18, 2013, 09:04 PM   #24
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Be thankful you bought the RCBS and not a Lyman, RCBS has great customer service I've had trouble with Lyman. Anyway, you may want to clean your scales once in a while. I use a paint brush to wipe the dust off every so often and a little rubbing alcohol, Cotton ball or wipes, to clean the knives and such. I have to clean a little more often as my bench is in my garage.
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Old January 18, 2013, 10:43 PM   #25
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I have had a 10-10 scale for 20 years and it still works great. I think a lot of the newer stuff is poor made. RCBS will stand behind their products 100%.
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