Drilling through Grade 8 bolts - Practical Machinist
2016-12-26 · Have job of drilling 150 1.250' Grade 8 bolts. Drilling through on centerline two.125 holes and one .1875 hole. Holes are used for grease system after bolt gets all modifications. Currently using hss centerdrill and 135 degree cobalt hss jobber length drill bits.Machine is 20+ year old Okuma mill in well worn condition. Mill only has flood coolant.
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