The main features of this light switch are 1) the spinning knurled knobs, and 2) the tactile “clicks” the lever makes as it is moved up or down. Other features include 3) a larger wall plate, 4) a separate plate ring to give a 2mm deep backing to fully cover the electrical box, while providing nice surface textures on the front & back of the plate, and 5) a slot in the rack for easier mounting to the electrical box. STL & STEP files included.

Designed for the single lightswitch style in North America as seen in the included picture. My location is Canada but think the US is the same.

This is an evolution of the SteamPunk/Geared lightswitch designs by 3D Printing World, JBV Creative and Bobby Bass. I've built all these designs but the first has limited movement and the handle would not always stay in the up position. JBV Creative has a design that uses a lever and  rack that moves the switch up/down and this model works well. Bobby Bass combined both designs nicely. However, I was looking for a more substantial handle and the feeling of a heavy SteamPunk gear to move. The result is a larger knob with a knurled emboss that rotates freely to make the handle provide pleasant operation. To simulate a gear, I used raised dots on the rack that mated with a series of dots imprinted (debossed) into the rack holder. 

As you move the lever, you can hear and feel clicks as the dots on the rack move in and out of the holes on the holder. This allows the lever to be positioned in almost any position without falling from its own weight. (See video below)

Rather than use a switch plate that required much support on the underneath, I designed a 2-part plate that results in nice surfaces on top and bottom. I also found that my electrical box (in Canada) required the switch plate to be slightly larger than some of the previous designs.

The original lever holder STL did not work in Prusa Slicer, as I believe it might be an open, surface body mesh. I fixed the STL in Fusion 360  and added the debossing.

The rack was modified with the embossed dots and a slot was cut into the top to allow easier installation on the wall electrical box. 

To make the knobs spin freely, I used a hex shaft to join the two knobs. I also replaced the round lever shaft with a hex shaft as these can be printed flat for added strength, without loss of function.

The only disadvantage of this light switch might be it can be noisy. 

Dec 29/24:  The rack has been modified to provide more symmetric operation. That is, if you centre the rack and attach the lever at right angles to it, you should have the light come on/off near the end of the lever's travel. Previously, you could see the light switch toggle on and off near only one end. The new rack is named rackV2.stl

All parts were tested with PLA. I printed most parts at 0.2mm, with 3 perimeters and 4 top/bottom walls. I used 15% infill. I often turned on the “single perimeter on ALL TOP SURFACES” feature.

For the hex shafts and the knobs I used 40% infill. 

All STL files are oriented correctly for printing.  (STEP files may not be)

The rack requires painted on support underneath and only around the slot opening. (See picture above for support position) The bridge lines should go across the narrow gap easily. (change bridge angle if they run lengthwise).

This design requires six M3x12mm (or M3x10) screws with a low profile head; such as a button or countersink style. 

While earlier designs glued the large gears, I found them difficult to position correctly. This design has each half-gear secured to the base plate with 2 screws. The screws also allow the switch to be disassembled if necessary. Glue permanently traps the rack and lever.

Two additional screws attach the 2 knobs to a hex shaft which should be just long enough to permit the knobs to rotate freely. 

If you need to modify any of the parts that I designed for your own use, I have included STEP files.

This short video demonstrates the switch in use and its assembly.