Spring Assisted Utility Knife

youmagine

Here is a video of how the blade functions: My print settings for this project (Cura): - 0.3mm layer height- 0.4mm nozzle size (important for supports)- Orient pieces as they are in the picture- 50% fill (you can do more, but I wouldn't do less)- Support everywhere grid style-nozzle size *2 = shell thickness-layer height *2 = bottom/top thicknessI printed all the pieces at once and then plated them simultaneously (Update: Plate the lever arms and blade on their sides instead of how it's shown in the Cura picture to increase strength). It took around 3 hours. To finish the parts, remove all support material and the 0.8mm supports included in the model (just make it look like the finished picture). Use a file to make the pieces fit into the body. My jerk is a little high so I have to file at the corners, but it also helps with making good fits on the fly. Make sure parts can slide smoothly and that their axle housing are not interfering with each other. File the 1/4" holes until a pin can fit in. Sand down any corners you want. Hardware: All of the hardware can be bought from McMaster-Carr (listed in bill of materials). The extension spring must meet several criteria or else it will not function properly. It must have an outer diameter of no more than 0.185 ", it must have a minimum length of no more than 1.5 " , but lower is more ideal, and it must have a maximum length of 2.8" or more. I found that this spring worked very well: http://www.mcmaster.com/#9044k19/=yicj7nCut the pins and bolts to size. Construction: Assemble in this order: Insert blade and lever into body, secure with pins and collars, secure spring with bolts and nuts while blade is in open position, secure razor blade. The only tricky part here is to squeeze the collars slightly while installing the blade to get a snug, but loose fit. In the end, the blade should not wobble around while it's open and when the lever is pressed the blade should glide out easily (the lever should not take much force to operate). If it's hard to open find out where the parts are interfering and file some more. Now you're done: Congratulations! You can now cut open boxes or anything else you need. Post some pictures so I can see your project come to life! And if you don't want to make one, you can buy one from me on Etsy: https://www.etsy.com/listing/244290158/spring-assisted-knife