huge fan of ingersoll gold twist. tips from: 6.0-25.9 mm TD0900013S4R01 0.3543 0.3898 0.55 0.500 1.15 1.77 2.920 9 KTD6.0-D9.9 NEW-167-14_Gold-Twist.pdf pro tip.. don't peck inconel 718 . chip gets work hardened and will smash your insert on re-entry.

I'd go with a Replaceable Drill Tip, depending on how the Casting actually cuts. Iscar makes a line called SUMOCHAM, that go down to 8 mm in size, and increment by 0.1mm increments. You'd need a 9.3 mm or 9.4 mm drill for a 7/16-14 Thread. About 100 SFM (may need to drop down to 60 SFM, based on the interrupted cut). This is the QCP-2M Geometry. Feed Chart shows 0.08 mm/rev, or about 0.003" per Rev., but that also may need to drop a little, based on the interrupted cut. QCP 093-2M 9.30 3.83 1.970 136 9.0 IC908 QCP 094-2M 9.40 3.81 1.990 136 9.0 IC908 There is the part numbers for 9.3 & 9.4 mm sizes. DCN 090-027-12R-3D 9.00 9.40 12.00 16.00 28.35 42.8 1.350 45.0 87.80 9.0 ICP 090 That is a drill body, with cylindrical shank, thru-coolant, 12mm connection size, 3.0-L/D ratio Here is a 8mm Milling Cutter, with 1.5/1 L/D Ratio on cutting flutes > That is a .315-Dia Cutter (in.), with .709" of Flute Length, and 7-Teeth. MM EC080H12R05CF-7T05 8.00 12.00 0.50 7 T05 7.70 18.00 36.0 3.0 0.03 0.10 IC908

What I've done in the past is drill to just shy of the crossover..then mill past the crossover and repick up drill after the crossover

Carbide insert drill, TSC and no pecking...

The casted .300 hole is your problem. Use a Highfeed cutter and plunge it first then come back and drill it. Drill life should go up exponential. Never chase a casted hole with a drill in Inconel. Mill it then drill it and think you will be happy with the results.

I've gotten good drill life in 17-4 with no thru tool by just slowing down on the pecks, running ~50% rate from HSMAdvisor. It seemed to avoid shocking the material so it didn't harden. I think I was getting about 50-60 holes out of a ~.08" drill, which was quite acceptable for the equipment we had. But it's certainly not max production!

Okay we are on the same page then. Thank you. Yes each part presents its own ways in which best to use the toolpath do to what we need.

From what I can tell, while the matching stepdown/up method may not work the best for a "3D" cavity, with drafted or contoured walls, it's perfect for a pocket, with nothing but vertical walls and flat islands and pockets.

Unfortunately Bob, I don't know the cost on these. Those Ingersoll Gold Twist drills are also great. I used a 'replaceable tip endmill' from Ingersoll, (5-Flute, 1"-DIA, .250 Corner Radius), to replace a beast of a 2"-DIA Bull, with 0.25 Corner Rad. The company making the old 2" Dia. Cutter had stopped producing the tool, so even though this was a "locked process", we were allowed to substitute this new tool, "provided the part geometry during this Operation Step was not changed". (Had to produce the same part feature, even though the path was different, based on the tool size changing. I'm used to paying anywhere between $40-150 "per drill tip", depending on brand, size, and application. There are really two benefits when you go with the replaceable insert tip: Tool Cost drops (typically), because you are only replacing a small amount of carbide, for a given insert No changing Tool Length Offset. The inserts repeat to within about 0.001" of length, as the thread form is ground in the insert geometry. Plus, no removing the shank from the holder, means your Operator can judge the wear, and replace the tip at the machine while another tool is running. You should be seeing 0.008-0.010 of wear on that edge, where the edges are wearing, but not chipping or pitting. I'm with Ron though > back off 30% on the amount of wear you would normally permit on an insert, when you are pushing an insert cutting in Steel. Shoot for 60-70% tool life. Better to change out that insert 10 holes early, than 1 hole too late... Since you need 10.1 mm, this also opens you up to Sandvik CoroDrill 880. These start at 10 mm Diameter, and go up in 0.1 mm increases as well...

Might be fighting some recast hardness at the cross section and might be at the threshold of what your going to get for tool life. Using replaceable tips was going to be my suggestion. Was doing some casting for one customer and every 4th hole we had to replace the drills. Might have got 6 holes per drill, but 4 holes was the accepted safe place and it was programmed accordingly. 30-50% of the total project anytime working with Inconel should be tooling cost. Other thing might be going through the one section. Then come back and machine the next section flat then drill again. IF there is too much interruptions for the drill it will eat them up quickly.

Wow, tried that on a part I'm working on. Awesome tip. Why didn't you tell me about that years ago???