small hole drill

[CNC-ERIC]

Hi,there,

 

I have consulted the related the topics in the forum, no answer for me.

 

four 0.6mm holes sit 0.7mm apart,only 2.5mm deep,material is Al 6061T6. 1/8" center drill drill 0.005", then solid carbide 0.6mm peck drill 0.11" rpm9950 feed 2.0ipm,Q 0.005",coolant, first hole is ok, the drill is just broken when just finished the second hole,I was wondering may be the wall of two holes too thin(0.1mm), so I tried increased the distance between the holes to 1.0mm,samething happened, drill was broken. so I check the runout of the carbide drill shaft holded in collet chuck, it is less then 0.0003", the tip to the measure point is about 0.5", is this 0.0003" runout ok for drilling the small holes?

 

then I change to 0.6mm HSS drill, rpm, feed,peck no change, drilled 48 holes, can you help me figure out why the carbide drill bit broken?

 

thanks very much

 

Eric

[EazyE]

Its hard to say- is the tip angle the same for both drills? also carbide tends to be a bit more brittle and chip or break easier than hss.. there has been allot of good things said about Guhring drills on the forum and I can vouch they are very reliable. Do a search for Guhring and check out some of the things these people are doing with them.. hth.....

[Saultspics]

Is the coolant high presure? I have had the high presure coolent brake small tools.

[generaldisarray]

Your parameters look good.You might try Halving your feedrate.I looked at an old proven program here for small holes it was

#80 drill

S90000

G99 G83 z-.22 R.03 Q .006 F10.

 

So if we had your rpm to a factor of 9

Try 1/9 our feed = 1.111

 

Is your drill breaking upon breakthru into another hole?

[CNC-ERIC]

thanks for inputs.

 

machine isHAAS VF2, the coolant is not high pressure, actually I adjusted it just blow away chips,the holes are blind.

 

My question is :

does the 0.0003" runout cause the drill broken, how about your machines runout?

 

the dial that I used is 0.0005" graduation. 0.0003" based on estimate.

 

thanks very much

 

Eric

[taperlength]

Is the center drill doing the holes in the same order as the carbide drill? Backlash in the machine could cause the center drilled spot to be off a few thou from the drilling location.