Reddit reviews HDPE (High Density Polyethylene) Round Rod, Translucent White, Meets ASTM D4976/UL 94HB, 1" Diameter, 2' Length

Agreed with other posters; the plastic material is overwhelmingly likely to be HDPE. Maaaaybe nylon, but probably HDPE (given its semi-translucent appearance). HDPE is food and medicine safe, dishwasher safe, tough as nails, and easy to work with.

If you're thinking of sourcing materials locally, look for a store like TAP Plastics (this is my local plastic retailer on the west coast of the US). You could also order the stuff and have it shipped; here's a 2ft length of 1" HDPE rod on Amazon for $17.00, which would give you plenty of material to make lots of utensils.

That screw on the top is a stainless, pan head hex (or socket) cap screw, which is a nice fastener but not exactly the right thread for the material (HDPE can hold threads, but the thread type on this metal screw could easily strip it out... I know I sound fussy about the fastener specs, but it matters in this case, since you want to avoid having the screw loosen itself all the time). A better fastener would be one intended for plastic; you want thread rolling screws to get the right anchoring in the plastic. You can find a 50-pack of 1",stainless steel pan head thread rolling screws for $6.44 (again, on Amazon). You'd drill a pilot hole in the HDPE bar that's smaller than the screws' thread diameter, and the screws will self-tap and get good "purchase" in the plastic.

For the thumb detent/brace, this again is HDPE sheet that's been formed into that specific curve. The nice thing about HDPE is that it can be formed using a modest amount of heat; boiling water is all that's needed in order to get it malleable enough to easily shape it into the right profile. That looks like 1/4" to me. You can get HDPE sheet and cut it into strips using a plastic cutter ($5 on Amazon), then cut strips to length, form the strips to the right ergonomic shape, drill, and assemble. Here's a 1/4" thick, 12x12" sheet for $8.50.

Finally, to deburr and smooth the cut lines on the plastic, you can hit it with a propane or butane torch, with quick passes that'll melt the small burrs and help the other marks to level-out.

Another thing to note: this utensil adapter is precisely the type of use case where 3D printers shine, and I'm looking at my 3D printer and the quick 3D model of this I just built in CAD, and I know I can bang these off and ship them to you in no time. I hesitate, though, in recommending only 3D printed parts. I have hundreds of functional prints around the house/garage/cars etc, and I love making functional prints, but as good as I get at design, and the better the hardware gets, functional prints from desktop printers still have strength and durability limitations; extruded rod and sheet are just stronger.

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All links in the same list:

- 1" HDPE rod

- Stainless pan head thread rolling screws

- Plastic cutter

- 1/4" HDPE sheet