"家具用小五金" can be translated into English as "small hardware for furniture" or "furniture fittings".
"Small hardware for furniture" directly describes the category of items, emphasizing their size and purpose for furniture.
"Furniture fittings" is a more concise and commonly used term in the industry, referring to the various small components and accessories used in furniture.
Both expressions are acceptable, and the choice may depend on the specific context and audience.