1,036. Sharpening a Knife and Chopping Wood

Shvisas Yom Tov 4:9

On yom tov, we are not permitted to sharpen a knife using a sharpener but we are permitted to do so on wood, a shard or a stone. We do not publicize this ruling out of concern that people will come to use sharpeners for this purpose. The rule about sharpening on objects applies when the knife can still be used, albeit with difficulty, or if it was just nicked. If the knife cannot be used at all, it may not even be sharpened on wood out of concern that one will come to use a sharpener. Accordingly, it is not permitted to give a knife to an expert to inspect on yom tov out of concern that he may identify a defect and prohibit the knife for slaughtering, which will cause the knife’s owner to sharpen it with a sharpener. If an expert inspects his own knife, he may lend it to an untrained person.

Shvisas Yom Tov 4:10

Wood may not be chopped on yom tov with an axe, sickle or a saw but it may be chopped with the sharp side of a butcher's tool. One may not use the wide side, which is like an axe. The Sages prohibited using things like an axe, which is the normal weekday manner, because it is possible to chop wood on the day before yom tov. They didn’t prohibit chopping wood entirely because of the possibility that one will encounter a log that is too thick to catch fire, which would keep him from being able to cook. For this reason, the Sages permitted chopping wood in an unusual way. The Sages had similar reasons for all the different things that they permitted or prohibited.