Sharpening a Knife on a Festival for Learning and Practice

Sharpening a slaughter knife during Chol Hamoed for the purpose of learning and hand training for a student practicing knife positioning. I saw in a book called Shaarei Yosef, page 85, that Rabbi Fried forbids sharpening a knife for practice. The opinion also leans as explained in Siman 540 that only for the purpose of food preparation is it permitted to sharpen a knife, as it is a craftsman's work. Generally, craftsman's work even for the sake of a mitzvah is prohibited, as explained in Siman 544, section 1 in the Rema and Mishnah Berurah (like building a synagogue). However, there is still room to say the following, and hence my question: 1. Perhaps someone who is not yet a craftsman and is still in the learning stage, his sharpening of the knife is not considered "craftsman's work". 2. Even if it is considered craftsman's work, perhaps there is room to permit it due to the lost time of learning and practice that will not return after the holiday. 3. Perhaps all sharpening for learning shechita is considered practical learning of the laws of shechita and not just for the sake of a mitzvah, but it is a mitzvah itself as part of the mitzvah of shechita, so that if he needs to slaughter, he can sharpen a knife in this way. And learning Torah is not subject to prohibition even if it involves craftsman's work, like writing Torah scrolls for free, which is permitted.

Hello 

For learning purposes, it is permitted.