calibration weights. anyone ever make some?

[spitfire_er]

so i was thinking why couldn't i make myself a set of These in grains. i have brass, a lathe and i work in a lab with a scale (mettler ae 200) that reads to 1/10,000 of a gram that gets certified every couple months.

if i turned out a couple got them close, then weighed them and stamped the weight after doing the conversion, wouldn't you think that would get me a nice set of calibration weights in grains for my reloading scale?

 

[jlow]

One could of course make calibration weights, BUT if it is for your own use, it hardly makes sense since in order to make them, you will need a calibration weight to first make sure your balance is precise and accurate at the specific weight you are interested in and to have something to compare them to. So, if you already have the calibration weights to do this….

 

[amlevin]

If you've got the reference scale and are certain of it's calibration then "What was the question?"

Don't even need to have a lathe. Stainless steel washers of various sizes, just filed off to match the desired weight will work. It's what it does, not what it looks like, that matters.

 

[fguffey]

0.0001g = 0.0015432gr.

Good numbers, it is not recommended brass be used, I have a 30 piece Ohaus test set with 2 Ohaus beam scales in grams, one is a 4 beam, the other is 3 beam, with them I have 4 300 gram test weights, on one scale all of the test weights have a different weight, both beam scales agree.

I contacted a test weight manufacturer of test weights, they informed me the aluminum and stainless weight are the most stable and reliable, aluminum and stainless weights also cost more.

If you have access to the scales I suggest you use coins, it is not necessary to make the weights, nuts and washers of different weight can be used, sort by weight then organize them. The Container Store could be considered for a source for containers with divided compartments.

F. Guffey

 

[Lazydays]

making calibration weight on paper looks easy, but in the end is a PIA. I used to have to make calibration weights in odd ball sizes for balancers that check gas turbine wheels in jet engines. Just not fun, and you often waste a lot of time just getting close to the desired weight. Then after you get close you have to figure out away to wipe maybe a couple tenths of a grain off the weight. We used an Ohaus 304 scale for the longest time, and it was a nightmare! Went with a sealed up $10K lab grade electronic scale that was kept in a plexiglass box. Later we actually bought a half dozen Pact scales that worked plenty well. After you thought you were done you sent the pieces to the lab (usually made about 25 of them), and some would always come back being a tenth or two of a grain too heavy. Yet the scales virtually mirrored each other. The other problem I ran into for the longest time was that I could cut the bob weights to less than .0005" all over and the actual weight would be all over the place. I figured that the actual brass weighed differently from lot to lot. So everytime I had to make the weights I ordered in several bars out of the exact same lot. But they had to be made right as a turbine wheel is a serious bomb at high speed!
gary

 

[BoydAllen]

In the drawer where I keep my balance scale is a stack of coins that are clipped together with a piece of paper that has their weights written on it. I weighed them several times on an electronic scale that reads to .02 grain, that I calibrated using the weight provided by the manufacturer. Definitely not as fancy as your setup but to keep my tuned 10-10 reasonably honest, and to make comparisons, good enough.

 

[timeout]

I borrowed Tony Boyer's idea. When I have a charge weight that shoots well, I use a screw that is close, then grind or file it it until it is exact to the weight. After that, I can set it on my scale, or someone else's and check if the reading is correct. This just eases the mind a little that the scale is indeed correct.

 

[spitfire_er]

Alright, I'll elaborate a little. I guess I pretty much answered myself, but there are some good ideas posted, that I didn't think of.

Just recently picked up a RCBS (Ohaus) 304 to use for my precision reloading. Of course it's old and used, and I need to ether tune it up myself or send it to Scott Parker, if he even works on these. I did send him an email.

Therefor, I would like to have some known weights to check the scale. I was using a 505 scale for the longest time, but when I got the 304, like a fool, I sold off the 505 before I realized a second scale would be nice. Now i'm going to buy another 505 or an old Ohaus 505, 510 or whatever I can find a deal on.

Back to the weights, I guess I was thinking it would be nice to make them looks nice, but 100 grains is 100 grains. I wasn't too worried about getting it spot on any one weight. Maybe I'm overthinking this way too much. Just trying to find check weights made in Grains online and they are out there, but not in abundance.

I was going to make 3 or 4 and get them close using an electronic (cheapo hornady) scale, then take them to the lab, get an absolute weight, then mark them all.

I think I'll give it a shot, didn't think about not being able to use brass. I have some aluminum and SS stock I could use.

I like the screw idea too!


I

 

[Webster]

That's exactly what I did. I made my own standard. You need to have access to a laboratory quality scale. I used a sheet metal shear and cut a strip of stainless steel sheet metal about 1/8" wide. Tin snips will curl the metal, try to get a strip cut on a large sheet metal shear. You can trim it to several lengths to cover a weight range. You need the standard to be very close to an even number. You may have to sand and weigh repeatably. You can nip off 1/16" increments to get it close to the weight you want. I made three standards. The only one I use is 32.98 grains (about 1/8*0.030*2). I call it 33.0 when I check the scale. As you know lab scales are in grams you have to convert to grains. Laboratory scales are accurate to 4 or 5 decimal places. I used an engraving tool to mark the weight on each of my standards to two decimal places. You want to be close to an even number for your standard.
An interesting thing about beam powder scales is that the metal tab that moves between two magnets for dampening is not steel, it's copper.

http://www.ndt-ed.org/EducationResources/CommunityCollege/MagParticle/Physics/MagneticMatls.htm

 

[Webster]

I don't think I would use brass or aluminum. Cheap scales may come with brass standards. SS has a very thin stable oxide layer. Brass and copper may change weight over time because they build up an oxide layer with time. Al to a lesser degree than brass. I have no idea what the weight change is.

 

[spitfire_er]

Thanks for the info Webster. I have some SS I'll use.

would it be beneficial that have a couple such as a 100 gn or a 15 gn and a 25 gn, or would just one known weight say in the 75 gn or so range.

 

[Webster]

I don't see any reason to make standards outside of the range your interested in. You want to verify in the weight range you will be using. I would make a standard in the 28-33 grain range. Maybe a couple weights. I think the scales always check out OK unless they are damaged. What I do is put my 33.0 grain standard on the pan, set the slide weights for 33.0 and adjust the leveling screw to zero it. Also verify the beam moves freely. Nothing else is needed.

 

[Webster]

I just measured my 33.0 grain standard. This may help shorten your time to make a standard. It's 0.030" thick .255" wide and 2.4" long. If you cut the SS strip to .5" wide it will fit in the pan without overhang.

 

[bozo699]

I borrowed Tony Boyer's idea. When I have a charge weight that shoots well, I use a screw that is close, then grind or file it it until it is exact to the weight. After that, I can set it on my scale, or someone else's and check if the reading is correct. This just eases the mind a little that the scale is indeed correct.

Timeout,
That really isn't the reason for doing it it is so no matter who's scale you using just use the screw for the desired weight no matter the reading because you know it is your desired weight no matter the reading.
Wayne.

 

[Webster]

I understand stand. It was just easy for me to make a standard of a known weight at work. At flat piece of metal is easy to clean.

 

[BoydAllen]

If you make the weight the same as the desired weight plus the pan, you can use it to check when you have a question about the whether a particular charge weighing is right, by simply setting the pan and charge aside and substituting the weight, on either a balance or beam scale. Which reminds me of an idea that I had for the Chargemaster crowd. If you get a second powder pan, and do a little file work on the edge of which ever one is heavier, so that it and the original weigh exactly the same, you can start your next charge by swapping pans, and save the time that it takes to slowly put the charge in a case, if that is what you are having to do.

 

[amlevin]

I like the screw idea too!

Who doesn't, but I digress. 8) 8)

 

[Lazydays]

first of all, most all calibration weights that are certified are made of brass. Never seen any from copper, but have seen a few made of somekind of tool steel (not stainless). Now if the calibration weight is kept clean, and wiped down with a oil & lint free cloth (I used rayon or silk), it will repeat. Brass does tend to grow and shrink with heat, but gains no weight (as does steel). Aluminum is known to oxidize, and this will add weight from the build up on the surface.

Now an even better alternative to brass or stainless steel or whatever is to use a gauge pin. Maybe cut it back on the length, but I'd just go smaller or bigger. They are ground very close (about fifty millionths) with a very fine micro. This would be an easy start, and they are not expensive.
gary

 

[Webster]

Something I have wondered about. How accurate are the notches located that the heavy weight moves on? If I remember correctly very high quality standard weights are rhodium plated. We had $5000 plus electronic scales at work. The standard looked like Cr plated brass. You could weigh a fingerprint on these scales. Sorry if I am digressing. We could only use the standard as a daily check. They had to be ISO certified once a year by an outside company certified to do calibration. Sorry again for digressing. Most short range benchrest shooters still drop the charges from a powder measure. That's why they give their loads in clicks rather than weight. It really doesn't matter if the scale is accurate as long as it's repeatable. We decide what works best by trying different loads. It doesn't matter if the best load was determined as 33.2 grains on your scale if it was really 33.4. The important thing is repeatability of weighing. If you weigh a piece of metal then heat it up to about 150F and quickly weigh it, it will weigh less because you have driven off the water molecules attached to the surface. I think the change is beyond the 2nd. decimal place in grams for a piece of metal the size of a coin. I am not trying to start a P match. I learn a lot from this website and sometimes I like to pass on info I am aware of even if you think it's crazy stuff. Something I have never heard anyone talk about. Does powder absorb moisture on a humid day affecting weighing accuracy?

 

[BoydAllen]

There was an article on Precision Shooting that discussed this very thing. PM me.