▁that ▁is , ▁to ▁be ▁def lect ed ▁from ▁the ▁intended ▁center - line ▁of ▁the ▁bore , ▁causing ▁the ▁hole ▁to ▁be ▁mis pla ced . ▁The ▁higher ▁the ▁length - to - d iam eter ▁ratio ▁of ▁the ▁dr ill ▁bit , ▁the ▁greater ▁the ▁t endency ▁to ▁walk . ▁The ▁t endency ▁to ▁walk ▁is ▁also ▁pre empt ed ▁in ▁various ▁other ▁ways , ▁which ▁include : ▁ ▁Est ab lish ing ▁a ▁cent ering ▁mark ▁or ▁feature ▁before ▁dr illing , ▁such ▁as ▁by : ▁ ▁Cast ing , ▁m old ing , ▁or ▁for ging ▁a ▁mark ▁into ▁the ▁work pie ce ▁ ▁Center ▁p unch ing ▁ ▁Sp ot ▁dr illing ▁( i . e ., ▁center ▁dr illing ) ▁ ▁Sp ot ▁facing , ▁which ▁is ▁mach ining ▁a ▁certain ▁area ▁on ▁a ▁casting ▁or ▁for ging ▁to ▁establish ▁an ▁accur ately ▁located ▁face ▁on ▁an ▁otherwise ▁rough ▁surface . ▁ ▁Con stra ining ▁the ▁position ▁of ▁the ▁dr ill ▁bit ▁using ▁a ▁dr ill ▁j ig ▁with ▁dr ill ▁bush ings ▁ ▁Sur face ▁finish ▁produced ▁by ▁dr illing ▁may ▁range ▁from ▁ 3 2 ▁to ▁ 5 0 0 ▁micro in ches . ▁Fin ish ▁cut s ▁will ▁generate ▁surfaces ▁near ▁ 3 2 ▁micro in ches , ▁and ▁rough ing ▁will ▁be ▁near ▁ 5 0 0 ▁micro in ches . ▁ ▁C ut ting ▁fluid ▁is ▁commonly ▁used ▁to ▁cool ▁the ▁dr ill ▁bit , ▁increase ▁tool ▁life , ▁increase ▁spe eds