Have you ever heard 一个刀? I don't know whether it's used or not or how wide its usage spans, but I think 一把刀 may be more common.

As far as I know, measure words are optional and you can always fall back on 个 (which is what I did here).

I don't know if using 把 is more natural/common. If you insist, I can change it. Otherwise, you can add a second translation.

well, I would never say 一个刀 just like I would never say 一个马 or 一个书. (but 一把刀)
It was just a suggestion though, I'm not authoritative on Mandarin itself. :)

No, I'm really not sure either...

I learned a lot of my Mandarin in Xinjiang, where it is a bit different from the Mandarin in, say, Shanghai (due in part to the 少数民族). For example, I have a suspicion that the Uyghurs would consider using measure words as being "upper class", and that most of them would just speak with 个s everywhere. This might be some of that influence...

it's cool. as Mandarin is often based after local speeches, it's why I asked if you had heard it anywhere in 大陆台湾南洋, in which case I'd be fine with it.

Out of curiosity, would you use 把 regardless if it was a kitchen knife or a battle sword?

I think so. 一把剑, 一把切菜刀