Square Gears Tie Clip

A tie clip with a pair of rotating square gears that provide an interesting conversation piece.

Needed:

3D Printer (I used an A1 Mini),

PLA (any color)

Fusion or use my STLs to print

Slicer software

I Googled and Chat GPT'd for how to design a pair of square gears. The results were complex (to me), and provided only how to design small toothed (Module 1) square gears. My thought was that small gear teeth would tend to skip and get out of sync. I wanted larger teeth, which would stay in sync more easily. I also found several square gear designs that had very similar tooth patterns, which varied in size and frequency along each edge. They had larger teeth. They were successfully cut from foam in the presentation. So I "Print Screen" one and used it as the basis for my design in Fusion. Reference the above screen shot.

This is not a beginner tutorial on Fusion. It assumes a basic understanding of designing in Fusion.

Open Fusion and start a Sketch on the XY plane.

Save the CanvasBasic1.jpg to your PC or PRINTSCREEN the gear and paste into Fusion. The center needs to be placed exactly on the ORIGIN center point.

Draw straight lines from center horizontally and at 45 degrees from center per above drawing.

Draw a circle from the ORIGIN 46.1 mm in diameter. Scale the gear drawing so that its corners are tangent to the circle.

Under DESIGN, CREATE, INPUT SPLINE, trace 1/8th of the gear teeth. Disregard the four lightening holes.

Extrude the 1/8th of the gear just defined. Mirror the extrusion 3 times to make: 1/4 of the gear; 1/2 the gear; and the entire gear. Do this by clicking on the blue highlighted 1/8 gear, tap E, and extrude 9 mm. Create 1/4 of the gear by going to CREATE, MIRROR, click on the object and then the long diagonal surface. Ensure that JOIN box is checked. Mirror two more times to create the entire gear.

A critical dimension is the gear hole diameter. I found that a precise slip fit is has .23 clearance with myprinter. So, for a 6 mm OD shaft, the gear center hole has a 6.46 mm diameter. Finish the gear drawing by adding the shaft hole and lightening holes. You can use the drawing provided or make up your own lightening holes.

Move and copy the gear laterally so there are two gears on the drawing. Rotate one gear 45 degrees. Place the second gear corner 0.346 mm from the middle of the first gear. I found this works. The gears turn freely and do not ratchet out of sync. See above drawing. This defines the shaft locations. Proceed with the design of the base tie clip with its two shafts. See the drawing. The distance between shaft center-lines may be different from mine, depending on how similar are my gears to your gears.

Design the clip.

I used auto tree supports and placed the Base Clip on its side. I also applied random seams to minimize shaft anomalies. The shafts printed vertically provided much smoother gear rotations. But, the support removal took several minutes. The shafts printed horizontally had minor imperfections and did not provide smooth gear rotation. But, the support removal effort was minimal.

My STLs are provided below.