Toy OTF Switchblade (Double Action)

This is a toy Automatic OTF Knife I designed. What makes this design different from a typical switchblade is that it not only ejects the blade when the switch is pushed forward but retracts when the switch is pushed backwards. This means it does not need to be manual reset like a classic switchblade. It also means its very fun to play with.

Support removal and assembly instructions

The first step after printing is removing supports. There are supports on the handles, carriage, and blade. You can use the assemble animation liked here as a reference of what it should look like after supports have been removed.

A video showing how to assemble the design is linked here.

In addition to the 3D-printed parts this design requires additional hardware. It requires 3 screws, 2 springs, and 2 to 4 rubber bands. I have included the links to the exact parts required but they come in large packs that may not be convenient if you are making only one knife. A more affordable option would be going to a hardware store and finding substituents. You can also take screws and springs from a Nerf gun.

When assembling first check that the carriage (the part with the blade inside of it) slides freely inside the handles. Then check that the blade slides freely inside the carriage. If anything does not slide smoothly sand down contact surfaces. For the design to work properly the latch springs and rubber band tension must be just right. This can be calibrated my changing the number and type of rubber bands. For the springs I have I like to use two strong rubber bands (one on each side) and two weak rubber bands (one on each side). The design also works with asymmetric rubber band arrangements. Information about hardware specifications can be found below.

Springs - https://www.mcmaster.com/catalog/129/1492/9657K614
Screws - https://www.mcmaster.com/catalog/129/3372/90385A317
Strong Rubber bands - https://www.amazon.com/dp/B093Q2M536?psc=1&ref=ppx_yo2ov_dt_b_product_details
Weak Rubber bands - https://www.amazon.com/dp/B008X0A1NA?psc=1&ref=ppx_yo2ov_dt_b_product_details