I have been working on replacing a bird feeder pole that is basically just a bent piece of conduit that forms an arm, cantilevered out over the edge of our deck.
Because this is too far to reach safely to add more food for the birds, I needed it to swing around to where you can stand and reach it. For this, I used small, through-hole spring snaps to lock and unlock the arm. My example project—a birdfeeder arm/hook is not the point. The build help here is about the spring snap which can be used for telescoping pipes.
You’ve seen similar solutions with adjustable leg buffet tables from Costco, or on older (heavier) tent poles. The idea is simple: Drill a hole near the end of a 3/4” conduit pipe, then a matching hole a foot or more from the end of a 1/2” piece. Then, you slip the 1/2 inside the 3/4 such that the holes are on opposite ends. Slide them apart until you reach the point where the holes line up and SNAP—a little metal “button” pops out through both holes capturing them and locking them into position.
With several holes in the 3/4, you can lock a range of extension positions.
The key to this is a small spring clip (the button) that goes inside the 1/2” pipe. an example is pictured, but here is a link:
For whatever reason, these are usually called “Kayak clips” or spring snaps. I suppose they are used on kayaks for the oars? In any case, I used the 6mm variety. To install, you simply squeeze the ends together and push one inside the 1/2” pipe, then using a pencil or long screwdriver or something, you slide it down until the button snaps into your hole. Then, slide this pipe into your 3/4” and line up the holes. Voila, a locking telescoping mechanism.
For my project, I am not really extending the pole, but using this setup to disengage the pipes and allow them to rotate. Once my birdfeeder is replenished, I can rotate the arm back out and away from the deck and SNAP, it locks in place.
One issue is centering. Because there is some gap between the 3/4 and 1/2, I added some heat shrink covering around the 1/2 that is hidden up inside. This helps to keep the pipe from wiggling around inside and makes for a better connection. You also want to have the pipes overlap by some length even when locked and extended to give some strength.