Hi Everyone, I've done a bit of searching and reading on small hole tapping, lots of great advice. Sorry if some of my machining lingo is off...new to this part of metal working. Sorry for the long post.
A little background, been working with metal my whole life, fabricating, blackmsithing and tinkered in the occasional bit of lathe or mill work. My Dad's business picked up a fadal 4020 CNC a couple months back and I've been learning the programing (mastercam 2x and the G code) and been running it for him.
Currently I'm trying to get a small production run of parts done (for myself personally) that requires me to drill and tap 2000+ 3mm .5 holes, 3/8" deep in 6061 t6.
I've broken a few of what was suppose to be good spiral taps for the cnc and a similar number of what I was told were high speed/feed nachi SG-ESS drill 2.5mm bits.I was told to run somewhere between 7200-9700rpm and 760-980 mm feed rate. I was told not to peck drill with these bits. (did a run of parts using the same type of bit but a 3/8" bit in aluminum at their recomended speed and feed rate with no issues) This time I've drill less than 50 holes and have ruined a small number of half finished parts.
-I have been drilling the holes .525" deep so I'd have room for chips when tapping.
-I'm using a rigid tapping cycle running at 150 rpm, with a feed rate that I calculate out to be 2.9527" and going .375" deep
-All holes where first drilled with a #2 centering bit. Then the 2.5mm drill and then tapped. I'm using a flood coolant.
At this time I've given up on the spiral taps and have ordered a couple 3mm .5thread forming taps which will be here on Monday, and will be switching to #35 jobber nitro drill bits and planned to peck drill the holes.
Can you guys please give me some good starting numbers for feed rates and speeds. This project is starting to really get to me. I've been using a machinist book to get most of my rough numbers for feed rates and speeds, and then tuning it from there, but I can't afford to break many more bits on this project