Deep C'Bores in Mg

[Mic6]

Hey Guys, I need to put Deep counter bores in some Magnesium blocks.  I found some HSS long drills on MSC.  

http://www.mscdirect.com/browse/tn/Holemaking/Drilling-Drill-Bits/Metalworking-Multipurpose-Drill-Bits/Extra-Length-Drill-Bits?navid=12106289+4288175036+4288243942+4288174924+4288243940

 

The C'bores are Ø.75 x 8" Deep  sharp corner with .410 thru hole.  It looks like drilling the c'bore and the thru hole isn't to much of a problem.  Any suggestions on the C'bore tool to cut the flat bottom?  Final depth is 7.7

 

Also, with no TSC, would a .750 - 1.0 peck be sufficient?

[MIL-TFP-41]

Buy an extra drill. Grind a flat bottom on the extra. (Basically just do an end grind like you would on a 2 fl endmill) Drill out with the regular drill & take the point out with the flat bottom one. We do this a lot for one off parts.

[dstryr]

Buy an extra drill. Grind a flat bottom on the extra. (Basically just do an end grind like you would on a 2 fl endmill) Drill out with the regular drill & take the point out with the flat bottom one. We do this a lot for one off parts.

x2

 

I normally would get a cutter grinder to build me a step tool. They would add a pilot of the thru hole diameter to help stabilize the bottom when cutting it flat.

[Mic6]

x2

 

I normally would get a cutter grinder to build me a step tool. They would add a pilot of the thru hole diameter to help stabilize the bottom when cutting it flat.

 

Same here, but 1st quote from AB Tool was $700 and it had to be carbide tipped, so we just bought an extra drill for $100.00 and will grind it flat bottom.

[Matthew Hajicek - Singularity]

How often do you guys use ball tipped drills?

[dstryr]

Same here, but 1st quote from AB Tool was $700 and it had to be carbide tipped, so we just bought an extra drill for $100.00 and will grind it flat bottom.

Destiny in Santa Clara will grind a regular HSS/Cobalt drill into a step drill.

[Pilot Plant Supervisor]

I like spade drills from Allied for applications like this. You can get the inserts in HSS or carbide and in flat bottom.