Two people grinding each other sharper. The Japanese 'iron sharpens iron'.

What a Japanese person actually thinks
Warm and respected. It's what a coach says about two teammates who make each other better. Reads as someone who values the people who push them.

Meaning

Literally: cut + file + chisel + polish
Actually: Improving through mutual effort and rivalry — all four characters are stages of working a piece of jade or bone. From the Book of Songs.

Scores

Naturalness●●●●●

Well-known idiom, common in sport and education.

Coolness●●●●●

Four rare, beautiful characters, all with a stone or jade component — the visual repetition mirrors the meaning. One of the best on this site.

Watch out

low琢 and 磋 are uncommon, high-stroke characters. This one needs size and a careful artist.

On skin

切磋琢磨

Orientation: vertical

Mincho, vertical, large. Four dense characters in a column is the whole appeal — don't cramp it.