the gemara says that according to th man deamar that a sakin shel traida needs hagala every knife will have a problem of ever min hachai I dont understand why this is so only shver to that man deamar, even according to the man deamer of tzonen there is shamnunis of ever min hachai and you need hadacha.
The TAZ (YD 10:10) asks your question. In truth, it would seem that indeed, every knife requires Hadachah b'Tzonen, as Tosfos implies (Chulin 8b, DH Sakin Treifah). This is in fact the ruling of the Agudah, as cited by the BACH (YD 10).
However, the SHULCHAN ARUCH (YD 10:3) implies that a Shechitah knife normally does not need Hadachah at all, as the Shach writes (10:12). The TAZ (10:10) there differentiates and says that the Shamnunis that comes from Ever Min ha'Chai is not sufficient to require Hadachah. (It should be noted that the custom is to wipe the knife on the hair of the animal between each Shechitah in any case, YD 10:3).
Be well
M. Kornfeld