need help with scale - Page 2

SL1 · February 25, 2011, 03:42 PM

One thing that has not yet been mentioned is dirt on the knife edge and balance point of the mechanical scales. Just a little dust there will make the scale have accuracy and repeatability problems that can go to 1/2 grain or more.

I guess I was lucky to start with an RCBS 5-0-5 scale, and I was able to use a lab scale to make a bunch of check weights in 0.1, 1.0 1nd 10.0 grain increments such that I can make a pile of check weights that exactly match whatever charge weight I want to use. I then check my scale at that weight a few times during the process. The only reason I have found the 5-0-5 to drift was dust at the fulcrum.

I clean the dust with a Q-tip and a paper towel before I start, but it is possible to need to clean it again if it sets for more than a few hours without a cover.

When clean, I can repeat to 0.1 grains with it, based on the check weights.

SL1

Vance · February 25, 2011, 04:49 PM

That is what I was talking about. Repeatability. I could not get repeatability with a known weight check weight with either the Lee or Hornady scales. I can with the RCBS scale. Whether I have one or two watches is irrelevant.

engineermike · February 25, 2011, 04:50 PM

Ok, but what about the guy who used his scale to measure the powder that was placed into the load that was tested and that test data was placed in the load manual? What if his scale is off and mine is right and now i'm off and the pressures are way off/different.

Oh yea, I keep forgetting that I am replicating a load using my scale for my bullet that works in my gun. That may also be the reason there is a range, from low to high in the book.

They're right those 3 watches are messing me up...

Or maybe it was two? Now I am wishing I didn't have three scales...

Brian Pfleuger · February 25, 2011, 04:58 PM

Quote:

Originally Posted by engineermike

Ok, but what about the guy who used his scale to measure the powder that was placed into the load that was tested and that test data was placed in the load manual? What if his scale is off and mine is right and now i'm off and the pressures are way off/different.

Oh yea, I keep forgetting that I am replicating a load using my scale for my bullet that works in my gun. That may also be the reason there is a range, from low to high in the book.

Lab scales are orders of magnitude more reliable, repeatable and EXPENSIVE than any home scale. Besides, they are calibrated usually at fixed intervals by people whose job is to calibrate scales.

The reason there is a range in the book has little to do with scales and lots to do with variance between firearms.

engineermike · February 25, 2011, 05:39 PM

Who cares if lab scales are more reliable. I DON'T HAVE ONE.

Brian Pfleuger · February 25, 2011, 06:17 PM

Point being that you implied that the manual charge range is due to potential variance between your scale and their scale and also said:

Quote:

What if his scale is off and mine is right?

So, I'm simply pointing out that there's virtually no chance that YOUR scale is more accurate than a lab scale and the range of charges in a manual has little or nothing to do with any potential scale variance and everything to do with potential firearm variance.

prairiedoghunter · February 25, 2011, 08:19 PM

I have an exact copy of the hornady scale, bought it off ebay for 9 bucks. Its a piece of junk, will not repeat a measurement without calibrating every 10 minutes. So im in the market for a new scale.

longspurr · February 26, 2011, 10:04 AM

Cheap scale check – weigh dimes. Weigh several newish dimes. You can easily compare with people in other place and different equipment. Someone with access to lab grade equipment can chime in and tell us what variance they see in US dimes.
With my RCBS Powder Pro scale (accuracy verifed with Ohaus check weights) I weighed 10 dimes. All weights are in grains
35.3 34.8 35.1 34.6 35.2 34.9 35.2 35.1 35.2 34.7

Years ago I had 2 inexpensive balance scales for checking my powder & shot charges. I thought they worked fine – until I noticed that I could put the same bullet on the scale several times, and get different weights!!! I cleaned the balance point and looked for anything loose.
I never found the reason the 2 scales would not repeat a weight.

Note: I think a person should do a quick check of any scale EVERY SESSION. Same item put on the scale 5+ times. See what variance there is.

So I got an electronic scale. This was repeatable. The scale had check weights but they were much heavier than an average pistol power charge. So I turned to small items. Dimes & pins. I would weigh them just after I turned on the scale & check (see note above) to see if the weight was the same as last time.

If all good then reloading proceeded. I check my power approx every 50 round (dillon 550) and if there is much variance stop and find out why.

I now use a set of Ohaus class 6 check weights but the procedure is the same.

http://www.scalesgalore.com/omass.htm

**Unclenick** · February 26, 2011, 11:57 AM

If you work up a tuned load that's successful, go to Lowe's or Home Depot and get a coil of cheap stainless steel wire and clip and trim and file a coil of it to match that load weight on your scale. It becomes a permanent standard you can set any scale to. Just keep it in a jar or baggy to keep dust and airborne oils from adding to it.

I don't think I've run into a reloading scale yet that didn't vary a little depending whether the pan came to a rest starting on the upswing or on the downswing. I usually touch the pointer end of the beam lightly on purpose to bias all my weighing all in the same direction. You can clean knife edges, but I think they all eventually wear a tiny radius in their corresponding notches on the beam that has some sliding friction. The better ones all have some way to lift the beam off the knife edge for moving the scale around.

The main problem with the cheap scales seems to be in the transducers. Some have plastic beams, some are single support, some are capacitive transducers, some are semiconductor strain gauges. About all I know to do is buy by reputation and send back what doesn't work well, and keep doing it until you get one that works.

When I called him to verify that the scale he sells is in native units of grains, Brian Enos told me he's had no returns at all with it. For $75, it's probably a good place to start for an electronic scale. If you want a metal load cell 4-post scale, Sinclair has one for about $300. It's the least expensive I've seen with those features.

brickeyee · February 26, 2011, 12:45 PM

Quote:

I now use a set of Ohaus class 6 check weights but the procedure is the same.

Except for aligning electronic scales you do not need weights of high precision, just weights of KNOWN value.

At least some of the electronic scales use multiple wight combinations to both zero the scale and linearize it.

My old PACT scale uses a 20 g and a 50 g weight.

The 'calibration' sequence is no weight, then 20 g, then 50 g, then 70 g, the 0 again.

This allows the scale software to make corrections over each of the segments (0-20, 20-50, 50-70) and provides a wider accuracy range.

RCBS used to have a check weight set that contained small sections of wire for the smaller values.
Each was in a plastic envelope marked with the weight of the section to 0.01 grains.

Scale pivots need to be clean and dry.

Even a little oil on the knife edge degrades accuracy.

sserdlihc · February 26, 2011, 01:33 PM

From my experience, the Lee scale was not for me. I bought an RCBS Partner Elec scale and I have been thoroughly satisfied. I calibrate it before each reloading session.

Never have used the scale you are referring to, but if you calibrate the scale, then everything should be good to go. IMHO

**Unclenick** · February 26, 2011, 02:12 PM

Brickyee,

I have that same scale that I got with the Pact dispenser. The 20 gm weight was accurate, but the 50 gm weight turned out to be short by a tenth of a grain when checked on a lab scale. That's about the class 6 limit, so class 5 or 6 must be what Pact is buying. Since they are using it for linearizing, I added some aluminum auto body tape to mine just to correct that.

Longspurr,

Just to summarize your dime data:

Average=35.01 gr.
Std. Dev=0.24 gr.
Spread=0.7 gr.

That's a lot better than when I tried measuring thirty-five quarters one time and got several whole grains of spread.

I put together this Excel file of check weight tolerances by class. Left two columns are the same weights in grams and grains side by side, while the upper block is tolerances in milligrams and the lower block is tolerances in grains.

jwilson48 · February 27, 2011, 09:23 PM

i couldnt get my lee scale to repeat itself over and over. would for a while then would lose it for no reason. i ended up buying a hornady dispenser and scale. best 250 i ever spent!

February 25, 2011, 03:42 PM	#26
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	Dust? One thing that has not yet been mentioned is dirt on the knife edge and balance point of the mechanical scales. Just a little dust there will make the scale have accuracy and repeatability problems that can go to 1/2 grain or more. I guess I was lucky to start with an RCBS 5-0-5 scale, and I was able to use a lab scale to make a bunch of check weights in 0.1, 1.0 1nd 10.0 grain increments such that I can make a pile of check weights that exactly match whatever charge weight I want to use. I then check my scale at that weight a few times during the process. The only reason I have found the 5-0-5 to drift was dust at the fulcrum. I clean the dust with a Q-tip and a paper towel before I start, but it is possible to need to clean it again if it sets for more than a few hours without a cover. When clean, I can repeat to 0.1 grains with it, based on the check weights. SL1

February 26, 2011, 11:57 AM	#34
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	If you work up a tuned load that's successful, go to Lowe's or Home Depot and get a coil of cheap stainless steel wire and clip and trim and file a coil of it to match that load weight on your scale. It becomes a permanent standard you can set any scale to. Just keep it in a jar or baggy to keep dust and airborne oils from adding to it. I don't think I've run into a reloading scale yet that didn't vary a little depending whether the pan came to a rest starting on the upswing or on the downswing. I usually touch the pointer end of the beam lightly on purpose to bias all my weighing all in the same direction. You can clean knife edges, but I think they all eventually wear a tiny radius in their corresponding notches on the beam that has some sliding friction. The better ones all have some way to lift the beam off the knife edge for moving the scale around. The main problem with the cheap scales seems to be in the transducers. Some have plastic beams, some are single support, some are capacitive transducers, some are semiconductor strain gauges. About all I know to do is buy by reputation and send back what doesn't work well, and keep doing it until you get one that works. When I called him to verify that the scale he sells is in native units of grains, Brian Enos told me he's had no returns at all with it. For $75, it's probably a good place to start for an electronic scale. If you want a metal load cell 4-post scale, Sinclair has one for about $300. It's the least expensive I've seen with those features. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

February 26, 2011, 01:33 PM	#36
sserdlihc Senior Member Join Date: December 10, 2008 Location: S.C. Posts: 1,454	From my experience, the Lee scale was not for me. I bought an RCBS Partner Elec scale and I have been thoroughly satisfied. I calibrate it before each reloading session. Never have used the scale you are referring to, but if you calibrate the scale, then everything should be good to go. IMHO __________________ Familiarity breeds contempt, while rarity wins admiration. Aupleius If someone doesn't like you, that's their problem! Milton Childress

February 26, 2011, 02:12 PM	#37
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Brickyee, I have that same scale that I got with the Pact dispenser. The 20 gm weight was accurate, but the 50 gm weight turned out to be short by a tenth of a grain when checked on a lab scale. That's about the class 6 limit, so class 5 or 6 must be what Pact is buying. Since they are using it for linearizing, I added some aluminum auto body tape to mine just to correct that. Longspurr, Just to summarize your dime data: Average=35.01 gr. Std. Dev=0.24 gr. Spread=0.7 gr. That's a lot better than when I tried measuring thirty-five quarters one time and got several whole grains of spread. I put together this Excel file of check weight tolerances by class. Left two columns are the same weights in grams and grains side by side, while the upper block is tolerances in milligrams and the lower block is tolerances in grains. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle Last edited by Unclenick; February 26, 2011 at 02:18 PM.

February 25, 2011, 04:49 PM	#27
Vance Senior Member Join Date: January 16, 2011 Location: North Bend, OR Posts: 743	That is what I was talking about. Repeatability. I could not get repeatability with a known weight check weight with either the Lee or Hornady scales. I can with the RCBS scale. Whether I have one or two watches is irrelevant.

February 25, 2011, 04:50 PM	#28
engineermike Junior member Join Date: March 14, 2010 Location: Oklahaoma City Posts: 538	Ok, but what about the guy who used his scale to measure the powder that was placed into the load that was tested and that test data was placed in the load manual? What if his scale is off and mine is right and now i'm off and the pressures are way off/different. Oh yea, I keep forgetting that I am replicating a load using my scale for my bullet that works in my gun. That may also be the reason there is a range, from low to high in the book. They're right those 3 watches are messing me up... Or maybe it was two? Now I am wishing I didn't have three scales...

February 25, 2011, 05:39 PM	#30
engineermike Junior member Join Date: March 14, 2010 Location: Oklahaoma City Posts: 538	Who cares if lab scales are more reliable. I DON'T HAVE ONE.

February 25, 2011, 08:19 PM	#32
prairiedoghunter Member Join Date: February 14, 2011 Posts: 19	I have an exact copy of the hornady scale, bought it off ebay for 9 bucks. Its a piece of junk, will not repeat a measurement without calibrating every 10 minutes. So im in the market for a new scale.

February 26, 2011, 10:04 AM	#33
longspurr Senior Member Join Date: November 8, 2002 Location: On the western shore Posts: 182	Cheap scale check – weigh dimes. Weigh several newish dimes. You can easily compare with people in other place and different equipment. Someone with access to lab grade equipment can chime in and tell us what variance they see in US dimes. With my RCBS Powder Pro scale (accuracy verifed with Ohaus check weights) I weighed 10 dimes. All weights are in grains 35.3 34.8 35.1 34.6 35.2 34.9 35.2 35.1 35.2 34.7 Years ago I had 2 inexpensive balance scales for checking my powder & shot charges. I thought they worked fine – until I noticed that I could put the same bullet on the scale several times, and get different weights!!! I cleaned the balance point and looked for anything loose. I never found the reason the 2 scales would not repeat a weight. Note: I think a person should do a quick check of any scale EVERY SESSION. Same item put on the scale 5+ times. See what variance there is. So I got an electronic scale. This was repeatable. The scale had check weights but they were much heavier than an average pistol power charge. So I turned to small items. Dimes & pins. I would weigh them just after I turned on the scale & check (see note above) to see if the weight was the same as last time. If all good then reloading proceeded. I check my power approx every 50 round (dillon 550) and if there is much variance stop and find out why. I now use a set of Ohaus class 6 check weights but the procedure is the same. http://www.scalesgalore.com/omass.htm

February 27, 2011, 09:23 PM	#38
jwilson48 Senior Member Join Date: February 17, 2011 Posts: 105	i couldnt get my lee scale to repeat itself over and over. would for a while then would lose it for no reason. i ended up buying a hornady dispenser and scale. best 250 i ever spent!