▁and ▁then ▁the ▁two ▁are ▁f li pped ▁over ▁and ▁the ▁core ▁segment ▁falls ▁out ▁of ▁the ▁core ▁box . ▁The ▁core ▁segment ▁is ▁then ▁b aked ▁or ▁hard ened . ▁Multiple ▁core ▁segments ▁are ▁then ▁hot ▁gl ued ▁together ▁or ▁attached ▁by ▁some ▁other ▁means . ▁Any ▁rough ▁sp ots ▁are ▁file d ▁or ▁sand ed ▁down . ▁Finally , ▁the ▁core ▁is ▁light ly ▁co ated ▁with ▁graph ite , ▁sil ica , ▁or ▁m ica ▁to ▁give ▁a ▁sm o other ▁surface ▁finish ▁and ▁greater ▁resistance ▁to ▁heat . Single - pie ce ▁cores ▁do ▁not ▁need ▁to ▁be ▁assemble d ▁because ▁they ▁are ▁made ▁in ▁a ▁split ▁core ▁box . ▁A ▁split ▁core ▁box , ▁like ▁it ▁sounds , ▁is ▁made ▁of ▁two ▁hal ves ▁and ▁has ▁at ▁least ▁one ▁hole ▁for ▁sand ▁to ▁be ▁introduced . ▁For ▁simple ▁cores ▁that ▁have ▁constant ▁cross - sections ▁they ▁can ▁be ▁created ▁on ▁special ▁core - produ cing ▁extr ud ers . ▁The ▁extr us ions ▁are ▁then ▁cut ▁to ▁the ▁proper ▁length ▁and ▁hard ened . ▁More ▁complex ▁single - pie ce ▁cores ▁can ▁be ▁made ▁in ▁a ▁manner ▁similar ▁to ▁injection ▁m old ings ▁and ▁die ▁cast ings . ▁ ▁Types ▁of ▁core : ▁cold ▁box ▁half ▁core ▁box ▁dump ▁core ▁box ▁split ▁core ▁box ▁left ▁and ▁right ▁core ▁box ▁gang ▁core ▁box ▁str ick le ▁core ▁box ▁loose ▁piece ▁core ▁box ▁ ▁Lost ▁cores ▁ ▁C ores ▁are ▁used ▁for ▁complex ▁injection ▁m old ings ▁in ▁the ▁fus