I talked about this in the past on this forum. I had a 1911 extractor go 'belly up' in a class. Larry Vickers was watching me when it happened and he asked for my gun, took a peak then told me "dude you're F'ed the extractor is toast". I grabbed a backup 1911 and continued. The next 2 reloading breaks during the class was enough for me to swap out the extractor and get the gun running again. Even Vickers was surprised. He noticed right away since my backup that day was a stainless gun and the 1911 that went down was black.
I pulled an Ed Brown extractor out of the wrapper gave it a tensioning tweak by sticking it partially into the into the extractor tunnel and torqueing on it. My field expedient tensioning was enough to get the gun running flawlessly for the remainder of the class. After the class I took the time to insure the extractor was tensioned properly.
In many cases you will find that a replacement extractor will not match the profile of the rear of the slide and typically some material will need to be removed. Then depending on the finish on the gun refinishing of the extractor may be required.
I'm convinced I know why my extractor broke. The weekend prior I was with Chuck Taylor (RIP) and ran a bunch of double feed drills (Type 3). The extractor took a beating being forced over a chambered round multiple times.
It was back to back Type 3 malfunctions that prompted Vickers to ask to see my gun. The clearance procedure for a Type 3 malfunction was worthless with a busted extractor. Most interestingly, I had practiced something that was A. useless when I needed it and B. the cause of my equipment failure.