Learn Farsi: قطعه‌سازان و ابزارسازان در کارخانه همکاری می‌کنند. - Parts manufacturers and toolmakers cooperate in the factory.

The suffix -sâz is the present stem of the verb sâkhtan (to make or build). When you attach a noun to the front of it, it creates a new noun meaning "the maker of [noun]". So, qet'e (part) + sâz = qet'e-sâz (parts maker), and abzâr (tool) + sâz = abzâr-sâz (toolmaker).

Why do these words use the plural ending -ân instead of the standard -hâ?

Because the suffix -sâz refers to the person (or group of people) making the item, it turns the word into an animate noun. In Farsi, nouns referring to humans traditionally take the plural suffix -ân. While you might hear -hâ in very casual speech, -ân is the standard, natural choice for professions and titles.

In written Farsi, why is there a half-space in قطعه‌سازان but not in ابزارسازان?

The word qet'e ends with a silent 'eh' sound, written with the letter Heh (ه). If you connected the -sâz suffix directly, it would change the letter's shape and ruin the pronunciation. A half-space (zero-width non-joiner) is used to keep it as one compound word visually without linking the letters. Abzâr ends in the letter Re (ر), which never joins to the left anyway, so it naturally looks separated without needing a special typed space.