"Tuning" a balance beam

[Tesoro]

The other day had a mishap on my reloading bench and a heavy box of brass fell off my top shelf and killed my 10-10 scale. I had read about the 'holy grail' ohaus M5 scale made in the 60's and found one on ebay like new in box but 40 some years old.

I set it up and its fast and relatively precise with repeatabilty to what looks like to me about .05 of a grain or maybe a little less (using various check weight combos). I had read about scale tuning services but no details were ever given as to how/what these guys actually do. It is not that expensive so probably not that complex.

I examined the scale with my 10x loupe and thought about how it works which is pretty darn simple! So to 'tune' a scale all I can see to do is refine the knife edge on the pivot arms. Also I noticed that when you put the pan on scale the pivot arms can move over and rest against the stainless steel back plate and cause additional friction. So I figure to take out dremel and jewelers rouge and polish up the steel ends and also round off the sharp edges at the end ( but not at the extreme bottom to interfere with the knife edge). And then superglue a needle onto the pointer and counter weight it with a portion of a lead shot in the base of the pan.

Other than that I cant see much else to do to improve the sensitivity which will equate to better repeatability. Is this what a 'tune job' is all about? Or am I missing something else?

 

[leatherstocking]

Can't be much help, but I think anything you do to add or remove weight from the beam, or anything attached to the beam will likely affect the calibration, linearity of the scale...
I'm no expert.
Btw, I'm waiting for delivery of a Lyman #1 scale which I just bought off eBay, which is also very old, hoping it will be in useable shape.
There is a guy named Scott Parker on one of the forums who tunes up scales, but not sure how, or how to contact him. Think he is on this forum, just search Sparker if yer interested.

 

[hoz53]

The other day had a mishap on my reloading bench and a heavy box of brass fell off my top shelf and killed my 10-10 scale. I had read about the 'holy grail' ohaus M5 scale made in the 60's and found one on ebay like new in box but 40 some years old.

I set it up and its fast and relatively precise with repeatabilty to what looks like to me about .05 of a grain or maybe a little less (using various check weight combos). I had read about scale tuning services but no details were ever given as to how/what these guys actually do. It is not that expensive so probably not that complex.

I examined the scale with my 10x loupe and thought about how it works which is pretty darn simple! So to 'tune' a scale all I can see to do is refine the knife edge on the pivot arms. Also I noticed that when you put the pan on scale the pivot arms can move over and rest against the stainless steel back plate and cause additional friction. So I figure to take out dremel and jewelers rouge and polish up the steel ends and also round off the sharp edges at the end ( but not at the extreme bottom to interfere with the knife edge). And then superglue a needle onto the pointer and counter weight it with a portion of a lead shot in the base of the pan.

Other than that I cant see much else to do to improve the sensitivity which will equate to better repeatability. Is this what a 'tune job' is all about? Or am I missing something else?

there have been threads on this forum in the past and also bench rest central. do a search and you will find some info you can use. One additional thing i can tell you is when you are changing weight in the scale pan holder. level the frame of your scale then adjust the weight so the pointer is on zero when the frame is level.

 

[rkittine]

Scott Parker tuned one of my beam scales. I think there is something new with the dampening magnets too.

Bob

 

[Tesoro]

Thanks for input. I did speak to Scott Parker but he is way too busy with life/work and only does scales in his spare time..so could be months before he can help and thus my d.i.y. quest.

I found the thread I had partially read a while back. Has all the info on tuning if you pick thru the squabbling by the digital scale guys. Funny the one thing they dont ever mention is if their digital scale will be working as well 50 years from now! Sometimes simplicity is good.

The english fellow allan from targetmaster, who developed the coolest automatic powder trickler for a beam scale, shares his knowledge on tuning. He also has some good youtubes with some neat inventions for the scales.

Heres the link fyi: http://benchrest.com/archive/index.php/t-75444.html?s=da63f82a490e4e0367371eed67fc3484

 

[hoz53]

Thanks for input. I did speak to Scott Parker but he is way too busy with life/work and only does scales in his spare time..so could be months before he can help and thus my d.i.y. quest.

I found the thread I had partially read a while back. Has all the info on tuning if you pick thru the squabbling by the digital scale guys. Funny the one thing they dont ever mention is if their digital scale will be working as well 50 years from now! Sometimes simplicity is good.

The english fellow allan from targetmaster, who developed the coolest automatic powder trickler for a beam scale, shares his knowledge on tuning. He also has some good youtubes with some neat inventions for the scales.

Heres the link fyi: http://benchrest.com/archive/index.php/t-75444.html?s=da63f82a490e4e0367371eed67fc3484

"simplicity ". thats what I like to. Please let us know how your scales comes out

 

[1066]

The english fellow allan from targetmaster, who developed the coolest automatic powder trickler for a beam scale, shares his knowledge on tuning. He also has some good youtubes with some neat inventions for the scales.

Heres the link fyi: http://benchrest.com/archive/index.php/t-75444.html?s=da63f82a490e4e0367371eed67fc3484

Thank you - I'm pleased you found some of my videos helpful.

 

[Tesoro]

Well its midnight and I just got done with the project. All I can say is friggin amazing! Here you go:

I did all the tweaks: honing (pita) adjusting the hangar wire, added a needle pointer added counter weight to pan for needle (popped brass stars out of spent primers n clipped off some legs for final touch) and polished ends of pivot. Little pencil graphite on knife and a few secret adjustmens along with a sprinkle of my special powder.

I have a bunch of lyman check weights and played with the linearity and repeatability at various weight combos with .5 grain min wt change in 20-60 gr ranges and it was as good as DEAD ON to what i guestimated to be max 15/100 of a grain variance on about 3 out of ten times per test at each weight range. Rest of times about 7/10 was right on the mark. When it was off by 15/100 was always under weight.

Then I got out some H4350 kernels which are reported to be avg .025gr each. I looked at them under a 10x loupe and then my 30x microscope and they were all very close in dimension just with or without a few chips on the ends. I did tests at 25 and 40gr and every 4 kernels would bring needle up to next graduation. Accuracy went down to +/- 1 kernel max after passing the 3rd graduation up. Which is not an issue and assume knife blades lose sensitivity when pass certain angle. And then I removed the kernels one by one and it went back down as evenly as it went up.

I found that blowing gently on the pan tp make some boiunce after first kernel drop at zero helped register it more accurately. But if I didnt blow the weight caught up by the 2nd kernel drop.

I zeroed on empty and then weighed 25gr and with 50gr and was within max .020gr always under and then I calibrated and dumped weights and checked empty zero. Was under by maybe same .15-20 gr. Tells me .20gr is the friction threshold for my knife blades with no load the way they are currently honed.I could prob do better than this if I get some diff stones.

It seems that once there is a load on the scale then the friction threshold is reduced considerably and the variance pretty much disappears when weighing in the 25-60gr. rifle powder weight ranges I tested.

I noticed the scale is now super sensitive to air movement. Breathing within a few feet moves pointer up and down in .025 gr increments but evenly so can still get a measure. A standalone plexiglass shield might be in the works.

I tried buffering the up and down swing with foam inserts in the copper plate slot and also under the pan. Fail. The scale works better going though the various magnetic fields to settle into the zero area. This happens about as quickly as my .03gr threshold strain gauge tanita diamond scale, BUT the gemscale wont react to light weight increments like the M5 so the gem scale is prob more like within .1-.2 avg on repeatabilty for a new user or better once one gets the hang of trickling up and feeling its threshold before it clicks over to next .05 increment.

I didnt have time tonite to trickle test the M5 but I can tell from my extensive test weighing that it will be a snap to bring up exact charges with constant light trickling of about .5 grain.

Anyhow bottom line is need to use check weights to re-zero close to or at your load to be spot on precise. Can easily make your own 4 pack set of .02gr weights out of ss wire to complement the lyman set so you can have any check weight combo to within .02gr.

And I see no need to experiment with the magnets on this M5.

My goal is to be able to weigh powder charges to the .1gr quickly and consistently. I now think a tuned up balance beam might be as good a tool and as fast as a good non chow mein magnetic or strain digitalscale. But the balance beam wont have a finite service life with possible giant repair bills and down time. And of course theres the cost factor. And then theres the cool factor of having a home grown 50yr old precision instrument as one of your main tools!

 

[rardoin]

Tesoro...nice work. BTW, My current lot of H4350 (as well as the last lot) weighs about 0.028-0.034gr per kernel so your 'lack of linearity' may not be as much as you think. I am a digital scale guy but I do keep a balance beam on the bench for back up.

 

[1066]

Good write up and good results..
You might think about something like this. Boyd Allen found Plexiglass may cause a static problem.

WIND BOX

 

[danny]

The other day had a mishap on my reloading bench and a heavy box of brass fell off my top shelf and killed my 10-10 scale. I had read about the 'holy grail' ohaus M5 scale made in the 60's and found one on ebay like new in box but 40 some years old.

I set it up and its fast and relatively precise with repeatabilty to what looks like to me about .05 of a grain or maybe a little less (using various check weight combos). I had read about scale tuning services but no details were ever given as to how/what these guys actually do. It is not that expensive so probably not that complex.

I examined the scale with my 10x loupe and thought about how it works which is pretty darn simple! So to 'tune' a scale all I can see to do is refine the knife edge on the pivot arms. Also I noticed that when you put the pan on scale the pivot arms can move over and rest against the stainless steel back plate and cause additional friction. So I figure to take out dremel and jewelers rouge and polish up the steel ends and also round off the sharp edges at the end ( but not at the extreme bottom to interfere with the knife edge). And then superglue a needle onto the pointer and counter weight it with a portion of a lead shot in the base of the pan.

Other than that I cant see much else to do to improve the sensitivity which will equate to better repeatability. Is this what a 'tune job' is all about? Or am I missing something else?

I think that you probably ruined your beam, or at least the knife edges, by rounding the ends of the knives You have increased the contact area that will be in contact with the aluminum keeper plates, which will increase friction.

Danny

 

[SheepDog]

I solicit used parts that reloaders have replaced and no longer need to donate to new loaders. Scales always need a good tune-up and I have done quite a few. Cleaning solves most problems but getting rid of friction caused by wear is usually necessary. I have test weights that go from 5 to 500 grains and found it necessary to test with full scale range to insure linearity. Sensitivity requires that the scales pivots never bind but they almost always do. That is why it can take several grains to get a beam to move from its rest position at the top and bottom of the beams travel. I don't know how anyone can do this work for money and charge less than the price of a new scale. I do it for free to get new people involved in the hobby. I also have refurbished presses, dies and powder measures.

Quick shameless ad: I am always in need of equipment so if you have any old stuff you don't use let me know!

 

[Tesoro]

I used my damaged 10-10 as the tuning guinea pig before I tried my M5! Just had to straighten some chinese tin metal and wire and other things! I practiced honing the pivot edges on it also. It is revitalized and I am giving it to a local friend who can use it.

 

[MrBottleneck]

The english fellow allan from targetmaster, who developed the coolest automatic powder trickler for a beam scale, shares his knowledge on tuning. He also has some good youtubes with some neat inventions for the scales.

Heres the link fyi: http://benchrest.com/archive/index.php/t-75444.html?s=da63f82a490e4e0367371eed67fc3484

Allan is a super nice guy very willing to go out of his way to help a fellow reloader with advice. Its a nice thing when a fellow member shares his knowledge that he has learned on the scales so others may utilize whats he has learned.
I am not aware of any scale Allan has not messed with. So, he is well versed in all of them I believe.

 

[Tesoro]

Tesoro...nice work. BTW, My current lot of H4350 (as well as the last lot) weighs about 0.028-0.034gr per kernel so your 'lack of linearity' may not be as much as you think. I am a digital scale guy but I do keep a balance beam on the bench for back up.

I just did a test weigh on my batch on my digi and it came out to .29gr per kernel in averaged in a grain. And then cross checked on my balance with the same kernels and then substituted kernels for a 1g check wt. What I learned is my digiscale - with reported .03 gr accuracy - would be off by one kernel but still read the same but the balance beam would show the difference immediately. However I am not getting obsessed over weighing to one kernel!

I dont know if I have been staring at my scale too much recently or what but when I look at the needle in the attached pick it hovers slightly!!

 

[MrBottleneck]

Now all you need to do is build a platform to secure the scale.
Incorporate a camera for your laptop and your are all set.
Just to give you an idea here is my creation.
It keeps the scale from moving when you change the poises etc.
As you can see it cannot move side to side nor forward or back as the adjusting foot sets in the inset bushing.
Super easy to read as I simply watch the laptop in fullscreen.
The platform/rest also has four adjustable feet.
Maybe my creation will help a fellow reloader that would like to make a scale platform/rest.

Here is where you can get the software I use for the camera. Its an awesome freebie that works fantastic allowing fullscreen viewing.
http://www.sharpcap.co.uk/sharpcap/downloads

 

[1066]

That's a neat job Mike.

 

[MrBottleneck]

Thanks Allan
Btw, Tesoro sounds like you have done a fantastic job.

 

[Tesoro]

Thx for tips. I have my platform for scale already. I also have a little usb borescope that works well. Have a mount and view full screen on my laptop. Pic above is taken with it.

 

[Tesoro]

I got obsessed with this friggin scale tuning experiment and went at it again today to do more refinements. I have now quit before my wife hauls me off to the psychiatrist. Pretty much have it to estimated .01-0015g off zero repeatability under load measuring 50 times by lifting the pan and resetting. And now 100% of the time it will noticeably register one kernel drop of varget which is .020. Trickle test worked great.

The main thing I learned from this exercise is to never use a balance beam for accuracy weighing without having check weights. Forget the zero when empty...just dial it in close and then use check weights to match your desired powder weight and then zero it. If you want sartorius style repeatability to the 10th of a grain every time then you need to zero at the pressure the knifes have on the bearings at the load you are weighing. At least thats what I believe and am gonna do from now on.