Step 1: Materials and Tools
Small piece of PVC pipe. I think I used 2 inch diameter, about 3 inches worth, leftover from a plumbing project.
QTY 2 #8x3/4 flat head wood screws
QTY 1 #8x1 flat head wood screw
QTY 1 3/16 x 3/4 "binding post" or pin with retaining ring
Pattern - attached later
Scraps of wood
Tools that I used, suggestions as to what one could use will follow in the steps where the tools were used:
Stationary disc sander
11/64 drill bit
3/16 drill bit
13/64 drill bit
Countersink for #8 flat head screws
Step 2: Flatten the PVC Pipe
Heat one piece at a time until it becomes soft and rubbery. Do this outside, I'm guessing it releases some fumes that you don't really want to breath. I used a heat gun (think a hair dryer on steriods), one could heat in boiling water or an oven. I'd avoid using an open flame, though placing it on a pan in a hot grill might work. Wikipedia says the melting point of PVC is between 100º and 260º C (212º-500ºF) I've tried the boiling water (100ºC) method and I don't think that is quite hot enough. Anyway, temp isn't important, soft and rubbery is. Experiment.
Once it is soft and rubbery, flatten out between two scraps of wood and clamp. High clamping pressure isn't really necessary, just enough to hold it flat. Allow it to cool. Repeat with the other half circle.
Step 3: Pattern
Cut around the perimeter of the A and B pieces of the pattern. Don't cut on the lines, leave a margin of about 1/8 inch or so. I used my sharp knife, use scissors if you like. Spray one of your pieces of PVC lightly with the spray glue. Stick a pattern to it. If you used 2" PVC pipe like I did, both patterns should fit on one piece. Print out another pattern and make two or toss the other piece in your scrap materials drawer/box for future use.
Step 4: Cut Out Pieces
Refine the shape by sanding to the lines. I did this with my stationary disc sander, sandpaper on a block of wood will work. If you're going with the 'by hand' method, it might pay to cut as close to the lines as you can. Perhaps use a file or rasp to get close before going to the sandpaper.
Deburr using a sharp knife. Don't cut with the knife, but rather scrape. Hold it so the blade is perpendicular to the piece and scrape.
Step 5: Drill Some Holes
For pattern A, drill the outside holes 11/64 inch and countersink for #8 flat head screws on one side. Drill the center hole 11/64 and do not countersink.
For pattern B, drill only the center hole. The outside holes will be drilled together at one time after bending. Drill the center hole 3/16 inch and countersink for #8 flat head screw.
I used my drill press to drill and countersink. A hand drill will work too.
Step 6: Bend the Ears
Clamp the 5/8 inch piece of wood on top of the pattern B piece, aligned with the dashed lines of the pattern. Clamp to the edge of a table or workbench with one "ear" overhanging as shown in the picture.
Heat the overhanging ear using the heat gun. It will likely try to curl and return to a tube shape just a bit, that's ok. Get it nice and rubbery, then using a scrap of wood, fold it up against the 5/8 inch thick piece and clamp in place. Allow to cool, then un-clamp and repeat with the other ear. I shot a video of me bending the second ear:
There's that heat gun again. This step would be a little more difficult without it. One could probably clamp the workpiece using all metal clamps to small pieces of wood and use the other heating methods, but it would be difficult.
Step 7: Drill the Remaining Holes
You're getting close. Heat the pieces gently one more time. Not so hot as to get rubbery, but hot enough to soften the spray glue. The patterns should peel off easily. Allow to cool and clean up any remaining glue with acetone on a rag (outside again). Hang the rag up outside to dry. Wadded up and thrown in a garbage can is inviting spontaneous combustion and a fire.
Step 8: Assembly