Wooden Weighing Scale (laser Cut)

Weighting things is usually interesting and often practical. Since I don't have an electronic scale, I had to guess weights by comparing. So I decided to build a low-tech scale! I came up with this idea, which is an adaptation of old concepts to today's DIY technology.

The laser cutter I usually use is not available for now, so I had to assemble my project virtually, hence the renderings instead of photos. As an open source project, contribution is welcome and perhaps an interested volunteer with a spare plywood board will test physically and validate my design. ;)

The slots of this design are adapted to a 4 mm (almost 3/16'') thick plywood but can be easily adapted to any size and material, using the plans provided.

If you don't have standardized weights, I made plans for them too. Knowing the density of a material, you can calculate (explained in the last step) the volume needed to obtain grams or ounces, and then cut it with the laser.

Step 1: Materials

• 4 mm plywood board (or plastic) : 37 cm x 44 cm (15'' x 18'')
• 3 small nails (for the pivots)
• glue
  

Extra:

• material for the weights (plastic or wood)

Step 2: Plans and Cutting

I tried to place the pieces as compact as possible on a rectangular board, but you can re-use scrap parts from other projects. 

Before cutting, make sure that:

• the size of the slots is the thickness of your material
• the 3 holes for the pivots are the right size for your nail (or whatever you will use)

Step 3: Assembly

Parts with slots are made to be inserted one into each other. Once the assembly is tested, it is possible to re-assemble it and add glue to solidify the whole.

1. Flat parts (the four pieces at each end of the main arm) need some glue; the thinner the layer, the stronger the bond.
   Insert nails or any small metal rod into the 3 pivot holes in the main arm.
2. The legs are spread and the inserted spacers should stay in place by pressure (press-fit). 

Step 4: Weights

Here's an example of how to create custom weights:

1. Find the density of your material:
      Plexiglass = 1,18 g/cm³
   
2. Determine how many cubic cm are required for the weight you need:
      volume = desired weight / density = 10 g / 1,18 = 8,475 cm³
   
3. Divide this by the thickness of available material, to obtain the area to cut:
      area = volume / thickness = 8,475 cm³ / 0,5 cm = 16,949 cm²
   
4. You can now cut any shape that has an area of 16,949 cm² and it will weight 10 grams!
   It is possible glue pieces together to make other shapes, like cubes.