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Your experience calibrating scales?

Discussion in 'Shooting Related Threads' started by joe kuhn, Jun 30, 2008.

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  1. joe kuhn

    joe kuhn Furry Lives Matter

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    A fellow shooter at our club was reporting heavy drops with a Mec busing #21. The powder is Longshot and we usually see about 21 grains from that bushing. He reported 23 grains.

    So I brought in my Lyman Scale Weight Check Set to the club and we checked it out. The 20 gr weight showed 21.6 grains. So he's actually shooting 1.6 grains less.

    This is significant especially if you're going to be doing any pressure and speed testing, which we're considering. Imagine if you were off in the other direction an equal amount. This could push you over the limit if you shoot some high pressures recipes.

    I wish I had the make on model of the scale, but I don't. It's electronic and doesn't show grains on the readout. You have to divide by constant to convert to grains. Will try to get these details later.

    My Ohaus 10.10 balance beam purshased used from someone here is right on the money. The 20 grain weight shows 20 grains.

    What's your experience?

    Thanks, Joe
     
  2. birdtracker

    birdtracker Active Member

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    Joe: beam scales are usually more accurate. Moving them requires resetting zero.Digital is quicker but can vary. Have a friend check your calibration weight with their scale. Moving a digital scale can influence weight.Having peace of mind requires checking and rechecking. I reload for my son also, so I want 20 grains to be 20 grains. Don
     
  3. tomk2

    tomk2 Member

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    Cold Temperature can effect the digital scales - learned that one winter in the garage. Weak batteries can also make them inaccurate - my cabelas digital scale would get goofy long before the low battery warning. Now I keep it plugged in. If the scale doesn't show grains, are you sure you are doing the math correct? Digital scales, especially the reloading ones, usually come with calibration weights. If this scale has no calibaration method, just a zero function, perhaps it is time to get a new, reloading specific digital scale? My RCBS 505 balance beam scale is always accurate, ready to go for when the digital scale seems troubled.
     
  4. BDodd

    BDodd TS Member

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    Joe, moving his balance beam from it's place at home to the club would have required it being zeroed in the new location eliminating any surface variations from one site to the next. You didn't prove a thing by just setting it up at the range and testing. The questions are does he just plop it down on the bench at home and expect it to weigh correct weights? Did you maybe do exactly the same thing at the range? Were I you, I'd go to the man's house and set his scale up, zero it where it stays, and THEN weigh how much powder is being dropped with whatever bushing. I fully support the digital scales, good ones, but they don't need the rezero polka every time it's moved from exactly one spot to another; the balance beam does.....Bob Dodd
     
  5. halfmile

    halfmile Well-Known Member

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    Just keep a bullet around and check periodically.

    HM
     
  6. BDodd

    BDodd TS Member

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    Halfmile's dead on, use a rifle or hand gun bullet of a known weight to check the beam often - no big deal.....Bob Dodd
     
  7. Trap2

    Trap2 Well-Known Member

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    I also use a PACT scale and have found it to be very accurate. I do not rely on battery power, it is plugged in whenever I'm reloading. I do have a habit of zeroing the scale in prior to each reloading session. I place the 20gr. weight on the scale, and if it says 20gr., I reload. If not, I would go through the entire calibration process to make sure it did. I have had the scale for over 4 years and have only had to recalibrate it once in all that time. It works for me and I trust it, and that is all that matters to me... Just my experience........Dan Thome (Trap2)
     
  8. Frank C

    Frank C Well-Known Member

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    I use a RCBS 502 beamscale. I find that the vibrations from the press (very minimal on fairly solid table) will "screw in" the zero adjust screw enough to have to rezero it significantly each time I check a weight. I always use the scale in front of the reloader, on a smooth piece of plywood that is screwed down to the table, very level. I may have to adjust the screw 3-4 turns to get back to zero. I have also noticed that the v blocks and the lever point on the beam itself should be centered, so that the metal lever point is not rubbing on the front or back, which would slightly obstruct the movement of the beam...just my observations and .02 worth.
     
  9. joe kuhn

    joe kuhn Furry Lives Matter

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    He's going to have to recalibrate his scale, but get this, the directions say to take 40 US nickels and then follow these steps...

    40 US nickels = the scale's max. Difference is spread across the range to zero.

    He did zero his electronic scale at the club before we checked it with the 20 gr weight.

    Thanks for the comments!

    Has anybody had a balance beam scale not check right?
     
  10. JJJ

    JJJ TS Member

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    When handling weights do NOT handle with your hands. I'm not talking about the body building type.
    It's better to use tweezers. I use Ivory tipped tweezers,the Ivory being softer than the brass weights.Now, however, the ivory tipped ones are hard to get.If you handle with your hands,sweat,lactic acid=no good.
    I use an Ohaus 1010, & a Pact electronic. Both are right on the money,except if the ceiling fans are running.
    I too,every now & then, check by using target bullets. It's amazing how the manufacturers can get such accuracy in the weight of their bullets.
    JJJ
     
  11. joe kuhn

    joe kuhn Furry Lives Matter

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    Yes, there's a tweezers in the check kit that I've got. The kit cost more than the scale, but it's the only way I know for sure what I've got. What if there was some dirt in the balancing hardware some where?

    Also note that zeroing a scale is different from calibrating. Calibrating for beam scales must happen at the factory. For electronics, the scale is set to zero and then calibrated which insures the accuracy of the scale across its range. You take a known weight at the top end of its range and put the scale through a calibration procedure. Any variation is divided across the range to insure accuracy. At least, that's the way it was explained to me.
     
  12. slowdp

    slowdp TS Member

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    The mechanical scale does not have to go to the factory for recalibration. But you do need to employ a scalesmith to have it done correctly. hehe - I is one - never thought I could use that line. For a meager $100 I will send you the brief instructions needed to do the job correctly.

    Now for a digital - using a 168 gr bullet to check the accuracy of a scale used to drop 20 gr of powder is not acceptable. 40 nickels is not an acceptable calibration weight but will get the scale fairly close. Let's see now - something about horse shoes and hand grenades comes to mind. Might you be unknowingly building a grenade?

    Digital scales (as well as mechanical) can exhibit linearity problems. A digital scale with an improperly adjusted overload stop will calibrate correctly with full capacity although the mechanism is resting on the overload stop during calibration. The weights at lower ranges will then be off. Also, a digital scale can be damaged by being picked up by the platter. The scale will be below zero with regard to the output of the load cell but the cheaper digitals will still show zero. The user will apply weight before the scale comes up to zero. This will result in a greater amount of weight being placed on the scale than displayed.

    Digital scales can also have a linearity error due to a damaged load cell or a problem in the electronics. The scale will be accurate at the calibration point but inaccurate at all other points. The amount of inaccuracy is uncertain and cannot be determined without several different weights.

    The zero point of digital scales will be set during the calibration procedure. The zero button is only to do a quick zero alignment during usage and is ofter used to remove the weight of the powder scoop. The calibration of a digital scale is normally accomplished at a point at or near the capacity of the scale.

    As noted in several of the above post, the scale should be checked with a weight close to the actual load being weighed.

    Don't let the dancing digits fool you into thinking the accuracy of a digital scale is certain. Make sure the scale is level and all feet are touching the table it is sitting on. Use a stable table, Remove all drafts in the room or shield the scale. Check it often with a small weight derived from another scale. You will not know for sure which scale is accurate if the two scales do not agree unless you use a very light calibration weight that has been handled carefully.

    Be careful and shoot straight with a load that is not dangerous.

    I would, in most cases, believe the mechanical scale over the digital scale.

    My two cents worth that is normally sold for a penny!
     
  13. spitter

    spitter Well-Known Member TS Supporters

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    Joe:

    Remind yourself to bring your weight set on Thursday Night - I've got a little Hornady Magnetic scale I'd like you check out...

    Jay
     
  14. joe kuhn

    joe kuhn Furry Lives Matter

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    That's what my friend has. A scale that measures in grams rather than grains. You divide the grams by 0.06479891 to get grains. I wouldn't calibrate it with 40 US nickels. What kind of accuracy is that? Old nickels are worn.

    EE - how do you calibrate your digital scale.

    Jay - it's in the car.
     
  15. BDodd

    BDodd TS Member

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    Ditto EE for the most part....Bob Dodd
     
  16. Dave P

    Dave P TS Supporters TS Supporters

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    The 10-10's are somewhat of a pain in the butt to calibrate with or without a weight because of the 10th. of a grain screw you have to mess with. Maybe it's not all that bad but it annoys me. I prefer the 505 with the "slide" device. All RCBS is high quality stuff however.

    QUESTION: You mention using a bullet to calibrate. How close are they to being to the stated weight?
     
  17. joe kuhn

    joe kuhn Furry Lives Matter

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    It turns out he wasn't using all of the digits in the conversion. When he did the scale checked fine.
     
  18. Dave P

    Dave P TS Supporters TS Supporters

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    To those of you using rifle or pistol bullets, how accurate do you find the bullets to be. Do you reccommend target or ordinary hunting bullets?
     
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