Summary

Tool for installing 1/4" couplers into thick-walled 3/4" flexible plastic pipe. Holds the coupler/stinger straight while a C clamp forces it through an awl-initiated hole, locking it permanently into the pipe, providing a place to connect 1/4" drip tubing for garden irrigation.

Instructions

I had 3/4" black poly pipe running along fences, feeding various drippers, small spray heads, and soaker tubing. After 40 years, it got brittle and began to fail.
This size of pipe is no longer used for irrigation, having been replaced by flimsy 1/2" tubing. I couldn't find a direct replacement, but I found a much stronger pipe that's actually rated for water-meter to house purposes. It was about $1/foot, but worth it to me in order to avoid a complete redesign of my irrigation setup.
But the walls of this pipe are so thick and strong that I couldn't get the 1/4" stingers (also used as 1/4" to 1/4" tubing couplers) to penetrate. The stingers took enormous force to insert, and often bent or broke. So I designed this device to support and guide them, and it has worked well.
The tricky part is that the stinger cannot come out, once it's inserted in the pipe, so this tool has to be removable from the pipe and from the stinger without any cooperation from the pipe or stinger.
The stinger is supported up to the flange that limits its insertion, held between two identical mold-like forms that combine to form a square plunger. Everything else comes apart after insertion, with the square plunger being pulled further in the same direction until it comes free, whereupon the two halves come apart and free the tool for reassembly for its next use.
I start by using a sharp awl to punch a starter hole in the pipe, and align the tool by sticking the sharp stinger tip on that hole, then assembling it in place. Then use a 6" C clamp as shown to force the stinger in. Remove the C clamp, disassemble the tool, and load it with a new stinger for the next use.
I printed this in ABS, with 100% fill.

Irrigation Stinger Installer Tool