Does "as sharp as a needle" mean the same as "as sharp as a razor"? Literal and idiomatic
Examples:

The penknife is sharp as a razor / needle.
The old man's senile, but his wife is as sharp as a razor / needle.

Question

Does "as sharp as a needle" mean the same as "as sharp as a razor"? Literal and idiomatic
Examples:

The penknife is sharp as a razor / needle.
The old man's senile, but his wife is as sharp as a razor / needle.

Answer

There's really no difference.

If I thought about it, I'd think 'The penknife is sharp as a razor' implies that the point of the penknife is sharp (just like a needle), while the entire blade of the penknife is sharp if it's sharp like a razor. 
Honestly, I doubt many people would think into it this far.

Metaphorically, there's definitely no difference.

집에서 편안하게 언어를 배울 수 있는 기회를 놓치지 마세요. 경험 많은 강사진을 살펴보고 지금 바로 첫 수업을 신청하세요!