RCBS/Ohaus 10-10

[robroy]

I was loading some 22 Hornet and tried to get 10.5 gn of H4198 into the cases. First few were fine I thought. I was weighing each charge with the 10-10 and noticed that it was taking more from the trickler as I went along. The volume of powder in the cases was also getting greater. I stopped and reweighed the previous charges and none of them weighed 10.5 gn.

Has anyone had problems on the small end of the scale with this equipment? How much of an effect does dust have on a scale? The cover was left off for quite a while and I blew it off but it may need a more thorough cleaning. Could this be symptomatic of a damaged knife edge or damper?

[montana_charlie]

How much of an effect does dust have on a scale? The cover was left off for quite a while and I blew it off but it may need a more thorough cleaning. Could this be symptomatic of a damaged knife edge or damper?
Dust, by itself, shouldn't have any effect as long as there isn't enough dust to start becoming part of the material being weighed.

The primary effect of dust is it's extra abrasive quality when it is allowed to lay in the agate bearings long enough to increase the amount of wear on the stone...or the knives...as the beam works up and down when charges are being weighed...and during day-to-day vibrations on the loading bench.

That's why it's a good idea to have a separate shelf to set a scale on...keep the beam out of the mounts except when in use...and keep the dust cover on.

In your case, I would clean everything gently, and run some tests with known weights to see if the reading is on the mark.
Then, try trickling up to heavier weights to see if the beam changes smoothly and consistently...and if the reading is correct when you're done.

One good way is to take a small (stamp-sized) piece of cardboard of a known weight (like a grain) and cut it into five or ten pieces.
Weigh out a small amount of 'something'...like 5 grains.
Then, add the cardboard, one piece at a time, and see if the weight increases by the known weight of the whole cardboard stamp.

It would probably be a good idea to have another scale on hand for comparisons.

CM

[monkeymt]

The use of some rubbing alcohol on knives, beams and balance will go a long way in restoring the measures accuracy.
Mark

[Newfoundlander2]

The 10-10 is as good as it gets with current balance beam scales. If the scale is clean, and centered on a steady LEVEL surface and you're still getting wide variations chances are your bearings are damaged and/or the set-swcrews on the rear poises are working themselves loose.

[lylejb]

a can of computer duster / "canned air" will also blow out any dust quick and easy, just do it one part at a time. Don't set up the scale and let the air batter it around.

i've used a 10-10 for years, mine seems accurate to about .2 grains I know it's marked to .1 , but it just doesn't seem repeatable at that low. It was that way the day i got it, and hasn't chainged a bit since.

10.5 grains should be 1 notch on the beam, +0.5 on the dial. Mine has a small plastic screw to lock the dial in place. I use it because I once had a similar thing happen, and found i accedently bumped the dial.

[robroy]

Thanks all. I plan on cleaning with de-natured alcohol and q-tips and inspecting under magnification. If I see a rolled knife edge or chipped jewel I'll send it off to RCBS