Razor Blade Equal-Arm Beam Balance Micro Scale




Introduction: Razor Blade Equal-Arm Beam Balance Micro Scale

About: I enjoy everything

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.

Step 1: Aluminum I-beam Level

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

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

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.

Step 4: Center Support Rods

I cut 1/8 diameter threaded rods into 4 equal pieces (to a length of 6.5 inches). To determine the height of support rods; I measured all my hardware that will be placed at the end of the balance rod.

I measured and marked the spot on the rod with a permanent marker and place nuts on both sides. This is an old trick of putting nuts on both sides of the cut point; this helps in keeping the thread integrity. By using a power grinder with a cut off wheel, it made quick work of cutting the rod. I then used a file and belt sander to clean the cut ends.

Now the thread integrity trick: after cutting turn the nut off the thread. Typically by turning off the nut, cleans the treads well enough to allow you to freely use later (no rethreading).

I needed a 90 degree bend in the top of the support rods. I place 3 nuts on the end to produce a consistent spacing for the bend in the rods. I have learned the hard way of bending items without some kind of a jig. Not having a jig - using nuts works well. I placed all 4 rods with the 3 nuts being held in the jaws of my vise. I bend all 4 rods at the same time. This produced the 4 - 90 degree bends.

Step 5: Mounting Center Support Rods and Y Axis Razor Blades

I used brass knurl nuts on top as height adjusters and standard nuts on the bottom to lock the threaded rods.

I used brass light fixture nuts to use to hold the razor blades on the 1/8 thread rods.

I used a circular surface level to help adjust the rods to equal heights to create a parallel surface.
Once the razor blades are level, I lock them in place by tightening the bottom nuts.

Step 6: Cross Beam Assembly

I cut a 5/16 diameter threaded rod to 22 inches long.
I choose the 5/16 rod because it was the best fit to the hole in the heavy duty razor blade.  The single heavy duty razor blade will be used on the x axis. I locked the razor blade in the middle with a nut and washer on each side.

To keep the balance beam equal, I put the same type and amount of hardware on each side. I put coupler nuts (elongated nut) in between the middle and end of the rod. The coupler nuts will be used to adjust the balance of the beam.

The hanging hardware was made by cutting craft chain to hang loosely between two washers. The chain is linked by an oval jump ring, which is attached to a fishing swivel. A jump ring attaches the swivel to a treble hook. The treble hook had the points cut off with a side cutter. The points and barbs were file down dull for safety.

I wanted the plates to swing and swivel freely.

Step 7: Balance Plates (Scales)

I struggled in my mind what to make the scales out of. I was working on some copper plates and I happen to spot a tea infuser.

It was easy enough to break the welds to get the infusers free. I skipped over the note on the packaging of the infusers, that they were stainless steel. I went to drill three equally spaced mounting holes. Well once I saw the glow of my drill bit, I realized they were in fact Stainless Steel.

Oh I used my Autodesk inventor to create my drilling template. It was a little over kill but I wanted equal spacing.

Step 8: Plan B Scale Hangers

I wanted to drill small holes in the Scales; but no luck because of the Stainless steel.

Since I had my fishing tackle box out for the swivels and treble hooks; I pulled out some straight hooks. Well not all hooks are created equally, some are very brittle. I am glad I found that out now; instead of catching a world record fish, just to break my hook. Anyway, I found some good hooks put them thru the screen of the scales - in the three marked spots.

I then placed jump rings thru the eyes of the hooks. Once I had this done I cut and filed the points of the hook. The scales were mounted to treble hook.

Step 9: Plastic Shield and Mounting the Beam

I plan on displaying my scale at our local Gem and Mineral show, so I wanted to avoid and issues with the razor blades.  So, I cut two pieces of Plexiglas (acrylic) sheets 6 X 7 ¼ inches.

I mounted the shield using metal clips on the side of the I-beam.

I was a little concern of the support rods spreading with the placement of the beam.  But this is not an issue.

Step 10: Finished at Last

Finished Razor Blade Equal-Arm Beam Balance Micro Scale

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    8 years ago on Step 10

    I would de-barb the hooks for safety too.

    How did you zero balance it?

    By adjusting the log nuts?

    Fikjast Scott
    Fikjast Scott

    Reply 8 years ago on Step 10

    Thank you for viewing my instructables.

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

    Yes by adjusting the nuts.


    Bill WW
    Bill WW

    9 years ago on Introduction

    Nice work.
    When you actually want to weigh an item, what will you use for weights?

    Fikjast Scott
    Fikjast Scott

    Reply 9 years ago on Introduction

    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.


    9 years ago on Introduction

    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
    Fikjast Scott

    Reply 9 years ago on Introduction

    -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.


    9 years ago on Introduction

    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
    Fikjast Scott

    Reply 9 years ago on Introduction

    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.