HDPE is the plastic used in many household containers including gallon sized milk jugs. It’s a dense and highly versatile material that can be processed without many special tools and shaped with common woodworking tools. All of these qualities together makes HDPE perfect for the hobbyist!
If you do not see a #2 in the recycling symbol or the letters HDPE do not use it! It might burn at these temperatures and give off a nasty or harmful fume. Even with that said, you should always be working with this material in a well ventilated area.
I made a video a while back on processing HDPE using a blender and toaster oven. Well, I’ve been banned from touching the kitchen blender, So now I’m just rough cutting the plastic with a razor knife. Honestly? It works fine.
Last year I built a mallet out of milk jugs and at them time I process quite a lot of of the plastic that I didn’t end up using. It has just been sitting idle in the shop. So I heated up my oven to 325*F and melted down the plastic until it was translucent.
The time varies depending on volume and shape of the container. I would suggest lining what ever you use with parchment paper as the HDPE will not stick to it! The amount of plastic here is about 8-9 milk bottles worth.Next I added some colored containers. Lids from jars, old mustard bottles, and various other items. As you can see they are all pretty rough cuts.
I then returned my concoction to the oven for another 1 hour or so. I would suggest checking on it every 30 mins just to be certain you don’t have any issues.
I got into my head the idea of twisting the plastic to get a neat swirl pattern to it. Grabbing a lump of molten plastic with thin workshop gloves might not have been my finest thought, but after a bit of personal injury and pain I got some good twists from the material!
As you can see even after a short time the plastic was beginning to cool and harden. So I put it back in the oven just long enough to heat up and get soft again. It should be noted here, that this type of plastic will not get softer than the “taffy” stage at these temps. Just know, you are in for a bit of a workout with HDPE!
Once it had softened up, I transferred the plastic to mold I built out of plywood. The mold cavity is 2″ x 2″ by 6″ and should yield a nice sized turning blank. YOU NEED MAXIMUM CLAMPING FORCE, as this will help to eliminate air pockets and voids! After it is clamped, give it 12 hours to completely cool and harden.
The next day I unscrewed my mold to inspect my blank.
End result was about 1.25″ x 2″ x 6″ More than plenty for my handle.
After ripping the blank down to 1.25″ squared on the table saw (that cutoff went straight back into my HDPE scrap bag to be reused in the future) I then mounted it on my lathe and turned it into a cylinder
While shaping I discovered a bit of void that had formed during the molding stage. Looks like it’s time for patch job!
I heated up the area with my heat gun, and then used some of the shavings from the roughing process. (I put them in the oven @ 325*F on a piece of parchment page for a couple minutes)
Wait a bit for it to cool and turn it smooth.
Then wet sand through the grits. HDPE can be treated like any acrylic blank on the lathe. I took this up to 12000 grit with my MicroMesh pads. The HDPE is super slick and you will find it very smooth at this grit.
The downside of this material is that glue doesn’t bond well to it. For lasting hold, I would rather turn to a mechanical fastening solution.
I decided to use this handle with an ice cream scoop kit that I had. The kit called for a 3/8 hole and to use some 5 min epoxy to secure it in the blank, which was not good for HDPE. So in order to adapt this kit to HDPE I started by drilling a slightly smaller 5/16″ hole.
I then heated up the threads of the scoop with my propane torch. I didn’t need this to be cherry red or anything. Just hot enough to melt the plastic and make tight threads. You could use a die set, but I think this is much easier and honestly more fun.
Be careful! It’s really hot, be sure to use good gloves for protection.
After threading on the hardware, I simply parted it off the lathe and cleaned up the end with hand sanding.
I’m very happy with how this turned out, and I really like the fact that it was made from items that would have been discarded as trash! I also think my patch blends in quite well!