Instructables

Razor Blade Equal-Arm Beam Balance Micro Scale

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Picture of Razor Blade Equal-Arm Beam Balance Micro Scale
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I made it at Techshop. http://www.techshop.ws/

 

 This is my version of an Equal-Arm Beam Balance Micro Scale.  It is 24 inches long, 2 ¾ inches wide and 8¼ high.



 

 
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Step 1: Aluminum I-beam Level

Picture of Aluminum I-beam Level
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I wanted a stable foundation to use and mount the hardware to.  I looked at several materials and came upon this aluminum I-beam level. 
I removed the center bubble holder and tube. 
Then I flipped (reversed direction) one of the bubble mounts to use as the Y axis leveling, leaving the other end for the X axis leveling.

Step 2: Creating the legs

Picture of Creating the legs
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I am using threaded furniture glides for legs. I followed the drilling instructions for hardwood installation.  I used a 3/8 diameter drill to create the holes. 

Remembering some old milking stool logic my grandfather told me, I am using only 3 legs.  I put 2 for the x axis end and 1 for the y axis.

I hammered in the treaded inserts in reverse of the traditional application.  I wanted the inserts to protrude down from the I-Beam to provide strength and stability.  This also gives a cleaner appearance to the table of the I-beam. 


Step 3: Center Support Rod Mount

Picture of Center Support Rod Mount
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I wanted to thicken the center support rod mount cross section.  I used ¼ inch Delrin plastic for the top plate cut to 2 X 3 inches. I used sheet aluminum for the bottom plate cut to 2 X 3 inches

The bottom item shown is my index card template.  I transferred the razor blade hole spacing on to the template.   2 blades will run on the y axis and 1 on the X axis. 

Planning on using 1/8 diameter thread rod, I drill oversized holes by using a 5/32 drill.  The removed bubble mounting hole in the I-Beam posed a issue for the support rod hole positioning.   I ended up just filing some of the I-beam hole edges for the thru passage of the rods.

sconner15 months ago

I would de-barb the hooks for safety too.

How did you zero balance it?

By adjusting the log nuts?

Fikjast Scott (author)  sconner15 months ago
Thank you for viewing my instructables.

I’m glad there are other people that think about safety.


Yes by adjusting the nuts.

Warmly
Scott
Bill WW7 months ago
Nice work.
When you actually want to weigh an item, what will you use for weights?
Fikjast Scott (author)  Bill WW7 months ago
I actually use cut gem stones that I had I already know the weight of. If needed I was planning to use micro-cut wire pieces. Thank you for viewing my instructable.
foxpup11 months ago
It looks like a nice practical, thoughtful design. I bet it serves you well. (love the fish hooks) On first glance I would think its biggest weakness (and all devices have one or more) would be where the chain meets the main balance bar (Threaded Rod). I would worry about variance in effective length as the chain shifts. This may not be an issue if the chain is tight enough around the rod so the "loop" cannot shift. What you have built here is probably more than adequate in 99% of the applications out there and there would normally not be any need for razor blade pivots on both ends of the scale, total enclosure to minimize drafts, and thermal regulation to remove any bar length change issues. I have a bad habit of overbuilding things and like to chase after more significant digits in my measurements, but that may not be useful in your application. :-) Great Job!!
Fikjast Scott (author)  foxpup11 months ago
-chain meets the main balance bar * Well my thought process was to keep the chains loose. I wanted the scale or pan to fall straight down. Now that you brought it up. I probably should put a concaved bushing so the chain is not sitting directly on the threads. I can see that there is a probable binding or conflict between the chain the spiral of the thread. I put the two washers on either side to reduce binding. Over the years, I have observed a few balance scales and most seem to have focus on having weights or objects falling straight down.
-razor blade pivots *I agree
- Total enclosure *I agree; the shields I put in place are for wandering fingers. Drafts really drive me crazy. My thought of screen cup scales is to get away from a flat plate that things will roll off. The screen was to allow some air to flow thru to reduce swing. A full enclosure is not in the plans. I have a displace case that this will set back into. I really need dampers under both ends under the scales. Early on in my career, I used an enclosed balance scale to measure the loss of product due to environmental conditions on craft paint. I would spend two 8 hour days using the balance scale that was later reduced to 1 hour with an electronic scale.
- overbuilding *I have few scales in my collection, but when I am measuring my gem stones I rely on a pocket electronic micro scale. This project was for fun and for demonstration. I enjoy just looking at it. Overbuilding is a good thing. Thank you for the comments and looking.
ccrome11 months ago
Nice. What kind of accuracy can you get out of it? The razor blade pivot looks like it would be very low friction.
Fikjast Scott (author)  ccrome11 months ago
I have not run an analytical study on the accuracy. I have used it for comparative sorting of my semiprecious gems. Mostly, I have been using it for demonstrations. I have a shoe box of loose faceted stones that I am trying to classify. Thanks for comment and looking.