幸运的刀子可以用英文表示为 "lucky knife"。这个短语并没有一个固定的来源或特定的意思。它可能是一个比喻，用来描述一个人有幸运的品质，或者是一个拟人化的表述，用来形容一个对象有着幸运的属性。
下面是几个用 "lucky knife" 表示幸运的英文例句及其中文翻译：
"I always carry my lucky knife with me. It's been with me through thick and thin, and it always brings me luck."
(我总是带着我的幸运刀子。它一直陪着我度过了艰难的时刻，总能带来好运。)
"I found this old knife at a flea market, and ever since then, my luck has been on the up and up."
(我在跳蚤市场发现了这把旧刀子，从那以后我的运气一直都很好。)
"My grandpa always used to say that a lucky knife will never let you down."
(我的爷爷总是说幸运刀子永远不会让你失望。)