It's nice to have a thumbscrew to use as an easy way to tighten down a component after adjusting it without the need for a tool. Having enough of these in the correct sizes can delay the completion of your latest project, so lets just make them from scrap PVC.

Supplies

Parts

Coach Bolts
PVC Pipe (larger the better)
PVC Cement
Washers

Tools

Drill (drill press recommended, but a hand drill will work)
Threaded bar or a long bolt
Saw
Spanners
Hammer
Hole saw or jig saw
File or sandpaper
Something flat such as a sheet of plywood or a chopping board.
A heat source such as a mini oven or gas camp stove.
Acetone or fingernail polish remover
Rags

Step 1: Cut the PVC Pipe

The first step is to cut your PVC pipe into sections that can fit inside your mini oven. The PVC pipe you want is something larger as that has the best wall thickness.

You can cut PVC using nearly any saw, such as a handsaw or circular saw.

Step 2: Flatten the PVC Into Sheets

Turn on your mini-oven or camp stove and carefully heat the section of PVC pipe. You must keep an eye on the PVC during this process so you don't burn it! Also this should be done in a well-ventilated area as plastic fumes are probably harmful.

Once the PVC pipe has become soft place it between two flat surfaces and put something heavy on top or stand on it. Wait for the PVC to cool down and you will have a nice PVC sheet.

Step 3: Cut and Smooth the Discs

Use a hole saw to cut out a few discs of PVC. If you don't have a hole saw then you can use a compass to mark a circle and then saw the discs out that way.

The discs are normally a little rough at this stage, so the easiest way to clean this up is to use a piece of threaded bar to bolt the discs together. Put the other end of the threaded bar into your drill and either use a file or sandpaper to smooth up the edges.

You can use sandpaper on a flat surface to buff up the sides of the discs.

Step 4: Assemble the Parts

Now insert the coach bolt into one of the discs, these bolts have a little square at the top that stops them from turning inside the disc. You will need to gently hammer the bolt into the disc.

The next step is to put a small amount of PVC cement onto the disc and then place the second disc onto the bolt. Lastly, put a washer and nut on and tighten this down.

A small amount of PVC cement will probably squeeze out, you should wipe this off with a rag. A splash of acetone (or finger nail polish remover) on the rag will help clean this up.

If desired you can spray paint the thumbscrew whatever colour your project needs.