Introduction: Threaded Beavers (Extra Large Dowel Nuts) for Break Down Furniture From Recycled Plastic
I use barrel nuts to make some break down furniture in the past. Using a 1/4" x 20 barrel nuts only have a diameter of 3/8" and I wanted a bigger, wider diameter barrel nut with a 1" diameter to use in 2x lumber break down furniture.
I've recently noticed videos about how plastic is not being recycled. With the lack of options to recycle HDPE, I thought I'd make an attempt to produce a practical and re-useable product out of HDPE. Hopefully some of the techniques I used can be used for your own projects as I've learned that melting and casting HDPE is easier than I thought,
Noticing the two problems above, I thought I'd attempt to kill two birds with one stone by making a large barrel nut out of recycled HDPE plastic called the Threaded Beaver. Feel free to leave any questions in the comments and I'll try to clarify or explain to my best ability.
Tools to melt plastic:
- Amazon induction plate: https://www.amazon.com/AmazonBasics-1800W-Portabl...
- Cast Iron Pan: https://www.amazon.com/Lodge-Griddle-Pre-seasoned...
- or stainless steel plate adapter: https://www.amazon.com/9-45inch-Diffuser-Stainles...
- Propane torch: https://www.homedepot.com/p/Bernzomatic-WK2301-Pr...
- Scrap conduit (1" Inner diameter)
- Milk jugs
- construction hard hats
- bottle caps.
- 3M respirator
- Safety glasses
- Silicon Gloves: https://www.amazon.com/Gorilla-Grip-Silicone-Prof...
Wood for bench:
- Laminated pallet wood for the legs
- half lapped pallet wood for the backrest
- 3/4" pallet plywood
Step 1: Prepare the HDPE
- Collect HDPE (Following Arrows #2)
- Remove labels, wash off and dry
- Cut up HDPE into small pieces
See video link here @ ~2:30 mark for the prep of HDPE
Step 2: Melt HDPE
Melt the plastic using a ferrous/magnetic pan on an induction top. I set my temperature to 400 degrees F and it seems to melt quickly.
I had a scrap cylinder of steel which I was also able to heat up on the induction plate and it helped with rolling out the plastic into a sheet.
See the video link here at ~3:00 mark where I start melting plastic.
Step 3: CAST HDPE
I heated up a conduit/steel pipe (1" interior diameter) placed it on a hot piece of metal, then I slowly added the melted HDPE into the pipe. I used a spare bolt to shove more plastic in and would heat up the pipe if I thought it cooled to much.
After filling the pipe, I use a clamp and some 1" diameter plywood in the conduit to really get high compression in the conduit. I'm trying to keep the density of this HDPE as high as possible.
After clamping, the HDPE will tend to shrink so I'll tighten the clamps as the plastic & pipe cools.
Adding smaller pieces and compressing down frequently seem to get the best results but I haven't mastered this process yet. Let me know if you have any suggestions in the comments
See the video link here @ ~4:30 mark where I start to cast plastic
Step 4: Cut, Drill, & Tap the HDPE
After the HDPE cools inside the conduit/pipe, I found it to be easy to remove the casted plastic. I ended up cutting into 1" long cylinder with a handsaw then cut the cylinder in half.
I drilled a hole into the center, and tapped the hole using a 3/8" x 16 N.C. tap and followed the tap with the actual bolt I used.
To make the bolt easier to enter the hole, I also used a countersink at the bolt entrance holes.
One of the surprising discoveries to me was how strong the thread held. Even using my impact driver, I didn't seem to stirp the thread. I also installed some bolts adding a nut on the flat side of the Threaded Beaver and I'll check the differences as the temperature changes here in San Diego.
Step 5: Use the Threaded Beavers
Since I was in prototype mode, I just measured roughly where the threaded beaver was going to go and used a 1" forstener bit to make a 1" diameter mortise into the stretcher piece of wood. Using a 7/16" longer drill bit, I drilled into the end grain roughly in the center of the stretcher.
For 2x wood getting connected to the stretcher piece of wood, I ended up countersinking a hole for the hex head bolt and washer to sit nicely in. This is not necessary but I thought it make this bench look a little bit higher end.
My engineering education honestly got in the way of progress here. I was being super exact and you actually have a bit of play wit the holes and the location. Since the Hex head bolt and Threaded beaver hold these pieces in tensions, I learned that I could over drill the size of the holes and adjust the exact placement of the boards before fully tightening these bolts.
This bench structure I made was really just the bones of my bench, I cut some plywood for the seat and back rest which covers the structure.
Let me know in the comments if you like this design or not. I'm going to use this one but plan on making a nicer/higher end version with nicer wood soon as well so I still have some time to made adjustments
Participated in the
Big vs Small Challenge