noun
replacement blade; spare blade
Refers to a blade intended to replace a worn or dull one, commonly for razors, utility knives, or similar tools.
カッターナイフの替え刃を買ってきた。
I bought replacement blades for the utility knife.
この剃刀の替え刃はどこで売っていますか。
Where can I buy spare blades for this razor?
替え芯 is a replacement lead or refill for mechanical pencils, while 替え刃 is a replacement blade for cutting tools.
Compound of 替え (replacement) and 刃 (blade).