Drill Selection, Feeds and Speeds For Hard Bolts and Screws Questions?

Hi my name is Chase I'm new to this forum and do not have much knoledge about drill selection. So I thought I would ask the experts. I sent a fool out to pick up a couple carbide drills and he came back with 5 cobalt parabolics. I've broken three on the last three bolts and needless to say I'm fed up with them. I buying Carbide like I wanted to begin with.

My setup was clamping bolt in a tilting rotory table on a knee mill Center drilling with a #1 center drill hand plunging. drilling with #55 cobalt drill hand plunging spinning at 1500.

The handbook says I should be spining 2800 to 4000 I am going to go higher and lower to see if that helps.

I am debateing Strait Fluted carbide drills vs. Regular fluted carbide

135degree vs. 140degree

I would also like to know what you suggest for a spindle speed for a 3/64" drill a plunge rate

I also have a a couple of 3 axis CNC mills at my disposal the spindle speeds are limited to Manual knee mill 3600 Milltronics partner ~7000 I think HASS VF-4 ~8000 I think on the CNC mills if you think I really need to use them what would you sugest for a drill cycle peck depth, retract... I am not a very experienced cnc machinist (~100hours) but I am comptent and would appriciate any thoughts and sugestions regarding setup.

Thanks Chase

Reply to
Chase
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"Chase" wrote in news:1149655346.005157.191230 @i40g2000cwc.googlegroups.com:

Not knowing what the bolt is made of and how hard it is doesn't help. I would guess a medium carrbon steel somewhere in the mis 40's Rc. So I would run at 75 SFM and about .0002" IPR. Drilling hard steel with a small drill is a tough task by any measure. As far as drill point angle and flutes go, I would think that you'll be better off with a standard 118 degree point and a standard flute.

Don't dwell and don't feed too hard. IOW, use the CNC machines. Unless you have a friend with a hole popper. That'd make short work of the job.

Reply to
D Murphy

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