I have some old polymer clay that I wanted to revive, so I chopped it up in a food processor with a little mineral oil (I bought the food processor at Value Village for this purpose only).
I began kneading the clumps with my fingers but after a while it started to hurt and I still had a lunch bag full left to do...
I found a device online that was built to knead clay but I didn't have $180 in my budget for it.
So I made my own.
Step 1: The Materials
2x4s - One 12 inch (30.4 cm) long and one 15 inch (38.1 cm) long, these were leftovers from a previous job.
Aluminum Flashing - 10 inch x 30 ft roll, unpainted (25.4 cm x 9.14 m), 2 pieces cut to 3 1/4 inches wide (8.25 cm) each
3 inch hinge (7.6 cm) with screws
2 1/4 inch wheel (5.7 cm)
Lag Bolt, 3 1/2 inch (8.9 cm)
Spacer made from plastic water pipe, 3/4 inch long (1.9 cm)
Tools (not shown):
Mitre Box and Saw
Cordless Drill and Bits
Philips Screwdriver (+)
JB Weld (2 part epoxy)
Paint Brushes and Paint
Step 2: Bevel and Paint
I decided to fancy it up a bit by cutting bevels on the ends of the 2x4s with the mitre box then sanded them smooth.
You can see that I've already used the 2-part epoxy to adhere the aluminum to the 2x4s. I've pre-drilled the holes for the handle and the hinge so the screws won't split the wood.
Step 3: The Hardware
Close-up of the hardware and the assembled handle. The threads of the lag bolt fit tightly in the spacer/pipe.
The 2x4s are fully painted and I've attached the hinge to the bottom/long 2x4. I used the remaining screws to attach the top 2x4 to the hinge.
Step 4: Almost Finished Kneader...
The finished product propped open with a silicone block. Looking at it I thought it needed sides to keep the clay from falling out.
For the sides I used my coping saw to cut the 1/4 inch plywood to 2 1/2 x 9 inches (6.3 cm x 22.8 cm), a 6 inch long (15.2 cm) top with a 3/4 inch (1.9 cm) end.
Step 5: The Finished Polymer Clay Kneader
The finished Polymer Clay Kneader with a box of Super Sculpey and a block of Premo for size reference.
I painted the side panels white and secured them with screws (I did not use the washers pictured earlier).
Now it looks like a giant stapler.
Step 6: The Process:
I grabbed a bunch of minced clay from the plastic lunch bag and squeezed it together and put it into the Kneader.
You'll note the green tone. The clay was being coloured gray by the aluminum flashing so I covered it with pieces from a green plastic binder held down by two-sided tape.
Second picture: First mashing.
Third picture: Fold the clay and crush again. I have it backward in the kneader, the fold should go next to the hinge so the air bubbles will be pushed out.
Fourth picture: After 9-10 foldings/mashings a nice smooth pancake of clay. And my fingers don't hurt.
Step 7: Cost and Final Thoughts:
I had the 2x4s, plywood, aluminum flashing and paint on hand. I paid $2.00 for the hinge(s), 50 cents for the wheel, 60 cents for the lag bolt = $3.10 or so.
Even if I had to buy the parts new... $3 for the 2x4, $9 for the varnish, $2 for the hinges, $2 for a handle... $16.
I would use a large drawer pull or gate handle instead of the wheel. Or remove it entirely, I was pushing down on the top board more than using the wheel.
I might replace the short hinge screws with longer ones for more strength.
Maybe I'd put a loop or eye bolt by the hinge to hang it up.
I would use stainless steel instead of aluminum. If I could not find any steel, then I'd would use several coats of varnish. I used 10 inch aluminum flashing because I had it on hand, but the working area was 3x4 or 3x5 inches so I didn't such long pieces. A couple 3 inch square (7.6 cm) bench blocks would be great but cost they $30 each.
The sides were not necessary, the clay did not roll out at any time.
The flashing was lifting off the bottom 2x4, I think the epoxy I used was too old or I needed to rough up the underside of the flashing.
So if this works for you, great!