Translation guide
A cotter is a metal fastener used to secure two parts, such as a pin or wedge. In Japanese, this is expressed with specific mechanical terms.
コッターピン
cotter pin
A metal pin or wedge used to hold parts together, such as in machinery or bicycles.
The most common term for a cotter pin, a split pin used to secure a nut or bolt. Widely understood in mechanical contexts.
コッターピンを差し込んでください。
Please insert the cotter pin.
Literally 'split pin', this is a native Japanese term for a cotter pin. Common in technical manuals.
割りピンが折れている。
The cotter pin is broken.
A direct loanword for 'cotter', used in some engineering contexts, but less common than コッターピン.
このコッターは自転車のクランクに使われています。
This cotter is used in bicycle cranks.
In everyday conversation, 'cotter' is rare. Use コッターピン for the common split pin. For historical or specific machinery, コッター may appear.