Tips and Tools: Extruder Conversion E. Preston Rice and Madeleine Coomey

Appears in the March 2019 issue of Ceramics Monthly.

Add some power to your extruding with this modification of a hardware store purchase. Complete the new and improved tool with custom-cut dies for unique shapes suited to your work.

This project began with a discussion on the Ceramic Arts Network Community Forum (http://community.ceramicartsdaily.org). I am no longer able to pull handles like I used to due to arthritis of my right hand and an enlarged thumb. I was also not happy with the way the small hand-held extruder caused a line (and weak point) perpendicular to the die each time I cranked, every 4 or 5 inches. One reply to me was from Madeleine Coomey (Min), one of the other moderators on the forum. She wrote,“Pres, how about using an electric caulking gun? Ryobi makes an inexpensive one ($40 in Canada) with 500 pounds of push force. I know the battery and charger would be expensive, but if you already have those [it could be an inexpensive solution]?”

After about a week of thinking about it and researching on the Internet, I spent part of an afternoon at a big box lumber/hardware store and came up with what I hoped would be a solution. I customized an electric caulk gun to accommodate a customized PVC pipe and plunger.

Supplies

• Length of 1½-inch inside diameter PVC pipe, cut to 8 inches
• 1½-inch trap adapter (Solvent Weld, PVC Schedule 40, Everbuilt C9000)
• Electric Caulk Gun (1)
• One battery and charger kit

Modifications

Modify these parts with tools that you have available. I used a hand drill, vise, Dremel Tool with grinding/sanding bits and a cut-off wheel, and hack saws. Wear safety goggles and wear a dust mask when sanding or grinding metal or plastic.

Begin by cutting the pipe to 8 inches. A standard caulk tube is 8½ inches long, but cutting the extruder tube slightly shorter makes the plunger fit inside more easily. I used a hack saw to make the cut after marking evenly all around, turning the piece in a vise as I cut. A PVC cutter or power miter saw will also work. Bevel the inside edge of one end of the 8-inch PVC pipe to ease the fit of the plunger. I used a knife, files, and sandpaper to bevel this edge.

Next, cut off the narrow neck of the trap adapter for a collar to slide onto the end of the pipe to hold the die in place (2). Remove the plunger from the toothed rod of the caulk gun by loosening the center screw. Next, remove the screw that holds the metal backing plate and the plastic plunger together. A caulk cartridge is 1¾ inches in inside diameter. The inside of the PVC pipe is slightly smaller, at 1⁹⁄₁₆ inches in diameter. To make these diameters compatible, remove ³⁄₁₆ inch of material from both the plastic plunger and metal backing plate.

To keep the shapes symmetrical while reducing their size, I set up a lathe of sorts and removed material as the pieces spun. Mount a hand drill into a vise. Using a #10 screw, sandwich the plastic plunger between two washers tightened together with a nut. Put the bolt assembly into the drill, then, with the drill running, use the Dremel Tool and the grinding bit to reduce the diameter to approximately 1½ inches. Repeat with the metal backing plate. Smooth in the same manner with a sanding pad or emery paper/cloth (I used a diamond sanding pad) (3). Reassemble the plunger and backing plate on the toothed rod.

Custom Dies

Blank die plates can easily be cut from Plexiglas using a 2-inch hole saw, which cuts a plug that fits perfectly on the end of the pipe. When using the hole saw, cut nearly through the Plexiglas then flip it over and finish cutting from the other side. This helps prevent the softened Plexiglas from sticking to the hole saw.

Draw a design on paper, glue the paper onto the die blank, and cut using the tool of your choice. After removing the paper template from the Plexiglas, briefly run a heat gun on the low setting across the surface to soften and round the cut edge. The side with the smooth edges faces inward, enabling the clay to pass through the die with more fluidity. Dies can also be made from sheet aluminum, solid polyethylene cutting boards, or Baltic plywood. I create the templates for mine using a computer drawing program, print them out on paper, and affix the template to the blank die. I use a drill bit and a coping saw to cut the die and smooth with needle files.

Assembling the Extruder

Assemble the extruder tube with the die held in place by the collar (5) attached to the non-beveled end of the tube. Feed wedged and rolled clay into the beveled end of the tube, leaving a little space at the end for the plunger. Place the entire assembly into the caulk gun/clay extruder with the open end aligning with the plunger (6). Plug in your battery and starting extruding! Within 3 minutes, I had 4 clay extrusions that were 8 inches in length to use for making handles. They were smooth, had no cross lines from short pumps of the manual-type handle extruder, and the process was very easy on my hands. The benefits of using the power extruder go beyond health issues as it makes a better, more consistent extrusion.

After using this tool to create handles for 10 teapots and over 50 mugs, I have found that it has eased my workload. The handles work much the same as my own pulled handles, and I have a greater variety of extrusion designs to choose from for different forms (7). Beyond handles, I am looking forward to using this new tool to make walls for low trays, feet for platter forms, and numerous other items. As a multi-purpose bonus, I can still use the power caulk gun to caulk around the window and door frames of the shop!

the authors: E. Preston Rice is a potter, retired art teacher, a past ICAN Advisory Board member, and an active member and moderator on the Ceramic Arts Network Community Forum. To learn more, visit http://picworkspottery.blogspot.com.

Madeleine Coomey is a studio potter working in British Columbia, Canada, and also an active member and moderator on the Ceramics Arts Network Community Forum. To learn more, visit madeleinecoomey.com.