I make a lot of things with PVC plumbing parts. It's durable, its available, and best of all it's cheap! This is one of my favorite PVC hacks, the lock joint. It adds the twist to lock function to anything that uses PVC pipe, and it is super cheap. This project can easily done at home, but I made it at TechShop! http://www.techshop.ws

Just remember, this will not hold water, so don't use it for your plumbing projects!

Step 1: Gather Materials

This joint will use 1-1/2 inch PVC pipe

(2) lengths of PVC pipe 1-1/2
(1) PVC Coupler 1-1/2
(2) 1/8 inch pop rivets

PVC pipe primer and glue kit
Sandpaper (Coarse Medium and Fine)
1/8 Inch drill bit
3/16 Drill Bit
A sheet of paper
Pencil
Flat Paint (Optional)
Textured Paint (Optional)

Step 2: Mark and Glue

One coupler will be glued into the adapter to provide a secure base.

Clean the pipe to remove any dirt and debris. Dry it thoroughly.

Measure the depth of the coupling from the ridge to the lip of the rim.

Transfer the distance to the plastic pipe. Place a piece of painters tape around the pipe at the mark. This will keep the primer and excess glue off the visible part of the pipe.

Hold the pipe vertically to avoid glue running into the other side of the socket.

Following the manufacturers directions, prime and glue the pipe. Wipe off any excess glue and remove the tape.

Inspect the inside of the socket, and remove any glue squeeze out with a paper towel.

Note: I often skip the primer, because I am not making water tight joints. If you don't like the 'purple primer' make sure you clean the joint well.

Step 3: Mark and Drill for Pins

We need 2 holes directly across from each other, this is a quick method I use to line them up.

Measure the depth of the coupler divide by 2. Mark a 1/2 depth line on the outside of the coupler

Cut the paper into a 2 inch strip to make it more manageable..

Wrap the strip around the coupler at the 1/2 depth line and mark the end point.

Now fold the paper in half aligning the edge to the line and crease the paper.

Mark the crease. This is exactly half the circumference of the pipe.

Wrap the paper around the pipe and mark the hole locations.

Put the joint together.

Being very careful to drill toward the center of the pipe, drill through the coupler and pipe on each side.

Place 2 lines on the coupler and pipe above where you will drill holes. If you have painted the pipe and coupler, use masking tape to protect the paint from the line.

Fold the paper in half again, mark the crease.

Using the line above, mark 1/4 of the diameter on the fitting.

Rotate the pipe 1/4 turn.

Drill again using the same holes in the coupler being careful not to enlarge the hole.

Optional:

I like to countersink my pins and cover them up with putty later. If you like the idea, do that now.

Step 4: Sand the Joint

PVC pipes are meant to slide tightly into one another. Since we want to easily remove the joint, we need to loosen the connection. To do this you can either sand the socket or the pipe. It is more difficult to sand the socket, but I believe this gives me a better appearance.

I started with coarse emery paper and worked down to finer grits as I got closer to a sliding fit. It should just barely fit but not require much force to pull apart.

Tips!

If you plan on painting the PVC project, sand the socket. Painting the pipe will increase its diameter slightly and you will end up sanding the socket anyway.

If you plan on painting the project, do it now. Then set the pipe aside for a week so the paint has a chance to fully harden. When paint is 'dry' it is still pretty soft and damages easily. Letting it set for a week makes it more durable.

I recommend you do not use a textured paint (my favorite is 'Truck Bed Coating'). Textured paint will grind away the socket over time. If you need a textured finish, paint a flat base coat and then paint the textured finish coat over it with the joint locked together. In the last step you can see that this is what I did. Flat in the socket and textured on the pipe.

Step 5: Install the Pop Rivet Pins

Remove the pipe from the joint, set it aside.

Press the pop rivet into the hole in the coupler. Fully squeeze the tool until the rivet pops.

Repeat on the other side.

You now have two locking pins on the pipe!

Step 6: Enlarge the Holes in the Pipe

The rivet was 1/8 inch, but when we installed it it expanded to lock in place. We now need to increase the size of the hole to accommodate the pin.

Grab another pop rivet, place it in the tool, and squeeze it until it pops.

Find a drill bit slightly larger than the rivets final size. I like to drill a test hole in a piece of scrap wood and test it in to make sure.

On the pipe side of the joint, enlarge all 4 holes to the new size. Be careful to drill toward the center of the pipe.

Step 7: Connect the Dots

Using the paper as a guide, draw lines from hole to hole as shown. The hole with the line above it is where the pin locks.

Now draw a line from the second hole to the edge of the pipe.

Repeat on the other side.

Note! Pay attention to how the pipe will rotate, I once cut the horizontal slots in opposite directions!

Step 8: Cut the Slots

Using a hack saw or Dremel, cut the slots. Cut inside the line, and finish the slots with a file or sandpaper.

Step 9: Woot!

There you have it, a lock joint in PVC.

Slide it into the joint

Rotate it until it slides all the way in

Twist 1/4 turn to lock the joint.

I took the additional step of painting a base coat of flat on the pipe that goes into the socket and and texture on the rest.

Stay tuned for my next Instructable, Bungee Joints!