Utility Knife
Overview
Completed Fall 2023
This project consisted of designing and machining a custom utility knife holder. The part was modeled in Fusion 360 and produced with a Haas VF4 mill and Markforged 3D printer. The goal was to create a compact but useful tool with a unique look and feel. The final part utilizes an engraved diamond pattern to simulate knurling, giving the tool and excellent hand feel. In addition the blade uses magnets at the top and bottom of the blade travel, creating a satisfying experience to open and close the knife.
Design
The hobby knife consists of four parts. The base and lid are machined aluminum and contain the blade mechanism. There is a 3D printed carriage that holds the blade as it slides open and closed, and also servs as the thumb rest to push the blade out. There are magnets press-fit into the base and carriage that lock the blade in either the open or closed position. There is a smaller magnet to hold the blade securely closed while keeping it smooth to slide out, and two larger magnets that hold the blade more securely in the open position. The carriage is designed to have a snap fit around the features of a standard utility blade, which makes it possible to change out the blade should it become dull or broken. The diamond engraving pattern gives the tool a little more grip when you use it and also adds some detail to an otherwise flat surface.
Manufacturing
The base and lid are machined on a HAAS CNC mill. The toolpaths were programmed using Fusion 360. Each part required two operations; one to machine the outside profile and knurl engraving and one to machine the inside pockets for the blade and carriage. For the first operation I used versa grips as a low profile clamp to give myself enough room to machine the entire profile of the part. Since the parts were very thin and needed to be machined on each face I made a custom fixture plate to hold the part for the second operation. I didn’t want to mar the surface of the part so I used Mitee Bite low profile fixture clamps to secure the part to the fixture plate. The custom fixturing also allowed me to locate each part relative to the bore on the front of the plate so I could make the entire batch without having to re-probe my work offsets.
