▁and ▁fe eds , ▁increase ▁the ▁surface ▁finish , ▁and ▁aid ▁in ▁e ject ing ▁ch ips . ▁Application ▁of ▁these ▁flu ids ▁is ▁usually ▁done ▁by ▁flo oding ▁the ▁work pie ce ▁with ▁cool ant ▁and ▁lub ric ant ▁or ▁by ▁applying ▁a ▁sp ray ▁mist . ▁ ▁In ▁dec iding ▁which ▁dr ill ( s ) ▁to ▁use ▁it ▁is ▁important ▁to ▁consider ▁the ▁task ▁at ▁hand ▁and ▁evaluate ▁which ▁dr ill ▁would ▁best ▁accomplish ▁the ▁task . ▁There ▁are ▁a ▁variety ▁of ▁dr ill ▁styles ▁that ▁each ▁serve ▁a ▁different ▁purpose . ▁The ▁sub land ▁dr ill ▁is ▁capable ▁of ▁dr illing ▁more ▁than ▁one ▁diameter . ▁The ▁sp ade ▁dr ill ▁is ▁used ▁to ▁dr ill ▁larger ▁hole ▁sizes . ▁The ▁index able ▁dr ill ▁is ▁useful ▁in ▁man aging ▁ch ips . ▁ ▁Sp ot ▁dr illing ▁▁ ▁The ▁purpose ▁of ▁spot ▁dr illing ▁is ▁to ▁dr ill ▁a ▁hole ▁that ▁will ▁act ▁as ▁a ▁guide ▁for ▁dr illing ▁the ▁final ▁hole . ▁ ▁The ▁hole ▁is ▁only ▁d ril led ▁part ▁way ▁into ▁the ▁work pie ce ▁because ▁it ▁is ▁only ▁used ▁to ▁guide ▁the ▁beginning ▁of ▁the ▁next ▁dr illing ▁process . ▁ ▁Center ▁dr illing ▁▁ ▁Centre ▁dr ill ▁is ▁a ▁two - fl uted ▁tool ▁consisting ▁of ▁a ▁tw ist ▁dr ill ▁with ▁a ▁ 6 0 ° ▁coun ters ink ; ▁used ▁to ▁dr ill ▁coun ters ink ▁center ▁holes ▁in ▁a ▁work pie ce ▁to ▁be ▁mounted ▁between ▁cent ers ▁for ▁turning