Newbie help drilling&tapping 3mm .5 holes

[Pook]

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

[HelicopterJohn]

Hi Pook,

I have a HAAS TM-1P with rigid tapping.

I purchased a couple of 3mm X .50 Balax Coated Form Taps for use in a making an item that I produce on a regular basis. This was my first use of the rigid tapping option and my first use of form taps.

I am also using ONECNC XR3 CAD/CAM. The project I did last week called for about 500 qty. 3mm X .50 tapped holes at .5 deep. ONECNC offers a G84 Peck Tapping Cycle that allows three levels. The material being tapped is 6061T6 Aluminum.

ONECNC's Calculations for Rigid Tapping are as follows:
The spindle RPM is 711
The Feed Rate is 13.986

I am using a #34 Drill (For a Form Tap) and a Rich Coolant mixture about 12 percent.

I have run this program several times and probably have close to a 1000 holes tapped with no tap breakage.

My good friend Vern helped me along the way and all I can say is thanks to him I am having GREAT success utilizing the Rigid Tapping option on my machine. I am a hobbyist machinist and I am sure other professionals here on the forum can better help you but I thought I would give you a little imput from a novice.

I love form taps and rigid tapping!!!!!!!!!!

John

[Geof]

Originally Posted by Pook ....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...

Regardless of the drill bit used the advice to not peck seems a bit strange, and the feed seems a bit vigorous.

I would peck every millimeter or so, drop the feed to around 300 mm/min and run at 9700rpm.

[Pook]

Originally Posted by Geof Regardless of the drill bit used the advice to not peck seems a bit strange, and the feed seems a bit vigorous. I would peck every millimeter or so, drop the feed to around 300 mm/min and run at 9700rpm.

I thought so to, but for the price I paid for the bits I assumed they were correct

[Pook]

Thanks John, that gives me a good starting point.