RuneScape Classic Wiki
RuneScape Classic Wiki
The main RuneScape Wiki has an article on: Iron dart tips
The Old School RuneScape Wiki also has an article on Iron dart tips.

Iron dart tips are made from an iron bar at level 19 Smithing, granting 25 Smithing experience and yielding 7 dart tips. Using feathers with them will make Iron Throwing Darts, granting 1 Fletching experience per dart.

Smithing dart tips require the completion of the Tourist Trap quest.