Gem Hammers can only be used out of combat and will add a gem socket to the weapon. The amount of Gem Hammers needed to add a socket depends on the weapon (normal/legendary) and the amounts of sockets already added to the weapon:
|Socket Number||Gem Hammers Required|
|2nd||1 Gem Hammer|
|3rd||1 Gem Hammer|
|4th||3 Gem Hammers|
|5th||5 Gem Hammers|
|6th||8 Gem Hammers|
Note: Upgrading Legendary weapons requires Legendary Gem Hammers.