The secret seems to be LOTS of pressure and slow running. In one of Guy Lautard's Machinist's Bedside Readers he describes the Cole Drill They actually melt their way through rather than cut., still spendy though. Stellite drills are another method for steels above 50Rc. If you decide to use a Solid Carbide drill then you should be aware that they really need a rigid set up and won't tolerate a ANY flex, if there is flex then result "broken drill bit " I have a few Titex carbide ones, very spendy but very, very good, Any good Carbide drill will do the job, just bear in mind the rigidity issue When I worked for an aircraft engineering company we had some drill bits which would drill files and hacksaw blades, can't for the life of me rember what they were though but the word wolfram drills pops into mind. I've drilled HSS this way but it needs quite a lot of pressure to cut and so Andrew's comments about coolant would seem appropriate - small dabs are unlikely to do much. If it's just one or two small'ish holes I've had some success with cheapo spear-point tile drills. As for coolant either nothing or flood, dabbing with a brush or the odd squirt is useless. You can use a masonry drill bit (with a carbide tip) at a push, sharpen the cutting angle and use coolantĪs mentioned there are straight flute carbide drills specifically for hardened steels up to 65Rc. The main problem with carbide drills is that they are quite brittle and need to be used with care. It depends just how hard the steel is but carbide drills are the best bet. Will titanuim coated hss drill bits be sufficient? As above what do i need to do it I will use my mill as a drill press.
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