Need input on milling cutter

[speedtwin69]

I am presently working on some large 12" 45 degree cones with 2 hole patterns around the center. My insert drill won't let just plunge or peck through it. I have been spot face them with a 1" end mill down far enough to make 1" flat. Then I call up the 1" insert drill and poke rite thru.
The angle of the cones eats up 1" end mills really bad on the corners.
I have to go over 3.5 deep to break through.
Any suggestions or comments .

[ASTECH_CNCTools]

Dear speedtwin69,
Is the milling cutter are made of steel materials? Or just solid carbide? If not, you may change into carbide router bits, or regular taper-shank milling cutter,

Rotate speed: about 400;
F: 50;
No faster, or the cnc tools are easily broken.
Besides, water and gas are well given.

Hope it will help!

[speedtwin69]

Material is high yield 4140 , I use nothing but carbide.

[KenFoulks]

Where does the endmill break first? Is it possible to go from the other side? Can you re-engineer the part for easier manufacturing? You could consider using end-mills with a .035 radius on the corners. I would try a helical feed with a 4 flute 5/8" EM with rounded corners.

[speedtwin69]

Each part has 18 one inch holes, you can't come from the other side cause there is nothing to bite on. I have been using a 5/8" Hanita varimill to plunge and then circa. Interp a 1" spot then shoot through with a insert drill. I use to use a 1" end mill with .125R on the corners that I had custom made for some other project & they were expensive as hell. I tried to get the lathe dept. To leave them flat on that side so I could just shoot thru with the insert drill & then machine the 45 degree last, but they whine it will eat up inserts on their machines. The mills I use cost about $180 a pc. & that is no concern. It is the time that bothers me, I don't get paid by the hour. So I like to haul ass on all my parts. I think if I made a jig to come from the other side I would still have the same problem breaking out of a 45 degree edge. I have to make (50) of these and I lack (10) to go so I'm almost done with this order. I will come up with something different for the next order.