Don't judge the no so expert machining, but I have used it successfully a couple of times.  Insert far enough so the front notches are forward of the case mouth.  Tap out with a cleaning rod.  A pointed jag actually helps spread the hooks apart to grab the case.

Jack

It is sliced so it had some spring to it. I cut it on my little Harbor Freight bandsaw. Cerosafe works great but takes a bit longer. I watched Bruce Kirby do that for a fellow shooter in the middle of a relay at Tommy Mason’s range and both ha time to finish shooting. I have used a 1/4” dowel as well pounded in from the breech and back out from the muzzle.  My issues were with a 25-20 Win low wall and went away when, taking advise from Jerry Hartwig, I bought some Remington brass. Unlike the Starline reformed 32-20, Remington holds up better. 

Jack

Here's my broken shell extractor.  A piece of 0.250" rod drilled through for a convenient screw, counterbored at the end, grooved at the end, sawed for expansion.

The screw has a small hole for a finishing nail to hold while the wrench turns the nut to expand to grip the mouth of the case.  I made it long enough to work for .25-35 and .25 Remington if necessary.

Best thing about this one is that it seems to at as a talisman.  Once I had put all the work into it and took out the .25 WCF case that had broken, I've not had another broken case, that I can recall.