Oyster Knife

Materials: 17-4, Aluminum, Canvas Phenolic Sheet, Hardware

Processes: 3D Modeling, Composite 3D Printing, CNC Milling, Heat Treating

Tools: Haas VF2 CNC Mill, Fusion 360, Markforged Mark 2, Heat Treat Oven

About: The goal of this project was to quickly hone in on a oyster shucking handle shape using 3D printing, then machine the final handle shape and blade. 

Process: I decided on a shape of blade that I was comfortable with and set some dimensions for the overall size of the blade and handle. From there, I printed a bunch of different shapes so that I could test them in-the-hand before taking the time to machine some final units. I designing a blade to fit into off-the-shelf file handles like this, but decided I wanted a bit more from the handle. I might go back to this idea and make a larger run. 

I really wanted the bulbous, revolved shapes to work. They reminded me of an awl handle and seemed to give a ton of leverage. In reality, they were a bit unwieldy and felt awkward in the hand. I ended up going with a fairly straightforward shape. The final decision came down to whether or not to add a guard. In the end I went with small "guard" that was just really an integral part of the handle and gave some protection against slipping. 

Machining the blade was not overly difficult, but I did find that the material warped considerably after machining the first side. I had to use an arbor press to straighten the blades between operations. I slightly over-bent the blade to give it some preload against the fixture. I think this helped keep vibrations down. I used simple 2D contour toolpaths around the blade and some 3D toolpaths with a ball end mill to give it a scalloped look. 

The handles were slightly tricky from an order-of-operations standpoint but once I got a system proven things went pretty smoothly. 

Heat treating 17-4 is incredibly easy. Pop it in the oven at 900F, no oxidization shielding required, and after 4 hours you have your part clad in a thin gold layer of oxide.

Conclusion: If I were going to make more, I would spend the time to make some dedicated fixtures (something more than a block with two threaded holes). The first handle I made was out of aluminum and was too heavy, throwing off the balance. The phenolic handle was much lighter and had a good balance. The oxide is wearing off and leaving a cool patina.

© 2020 Parker Musselman