Key, 4x16 mm

For $2, you can’t really go wrong—machined cleanly and the 4×16 mm size matches the SC4-5 spec I needed. Took me five minutes to swap out, and the fit was snug without any filing.

It matched the SC4 diagram exactly, so I was able to swap out the old one in my lathe without any guesswork. The 4x16 mm size is precise, and it feels solid enough to hold up under regular use.

Ordered this as a spare for my SC4 and it dropped right into the slot with no filing needed. Nice that it's listed as part #5 on the diagram, so I knew I was grabbing the right one. Two of these in the drawer now for the next teardown.