Glossary
Cast-in threads — definition
Threads formed directly in the casting tool, with no subsequent machining.
Casting a thread is entirely possible, but the options are limited in three ways.
The tolerance is a casting tolerance, not a thread tolerance. The thread comes out coarser than a cut thread and does not fit as precisely.
The thread has to lie in the draw direction, or you need an unscrewing core or a slide core — both of which are expensive.
Wear. A cast thread survives a few assembly cycles, not many.
In practice cast-in threads are used for coarse threads that are screwed once and left. If the part will be taken apart, a cut thread or a threaded insert is the right choice.