Hi Rita, welcome to THR...
The Kahr/AO 1911 can be a little sketchy on dimensions sometimes. Have you measured the slide hole and extractor head yet? Is the extractor a few thousandths larger (or less), or is it seriously larger than the hole?
Yes, you can sand it, but unless Nowlin screwed up (not likely), I'd bet your slide is undersize... and you'll have this problem with every brand of extractor.
The extractor should fit with a bit of a push, but it shouldn't be a hard press fit or the other end of the spectrum, a drop-in fit, which seems to be the more common these days. How does your old extractor fit, and what is it's diameter?
Just out of curiosity, why change the extractor? Have you determined that your gun has extractor issues and decided to replace the extractor? If your original extractor is not broken, have you considered tuning it, or having it tuned?
The reason I mention this is because I've seen lots of threads over the years with Kahr/AO 1911 extractor issues, where proper tuning, not part replacement was frequently the cure.
C