"rangerssuck" wrote in message
...
On Thursday, March 3, 2016 at 3:32:40 PM UTC-5, whit3rd wrote:
On Thursday, March 3, 2016 at 9:36:02 AM UTC-8, Bob La Londe wrote:

This machine has an ER11 spindle nose. I would just get ER11 collets
for
each drill size, but anything under 1/8" is pretty much impossible

This application is for venting features in a mold...

Carbide 1/8" shank drills will only take me down to a depth max of about
3/8". Less on smaller bits. The plates are 1/2" thick

But you indicated this was for NC machining? So, can you pre-drill 0.250"
deep with a 0.130" diameter bit, then sink the microdrill the rest
of the way? I foresee some chip clearance issues still, but pecking
might work.

I had thought of back drilling he mold, and then flipping the plate to front
drill the vents before cutting the cavity, but I suppose I could back drill
both the clearance hole and the vent hole. I still have to do two setups
for every plate, but I guess if I plan for it I can make that a little less
tedious to index.

Great idea, with some changes for drill bits you can actually buy. With a
drill such as
http://www.mscdirect.com/product/details/71465157 you could drill .130 dia
.320 deep, hold .980 of the bit's shank in the collet and drill the
remaining .180 and still have .010 clearance between the collet and the
work, and .010 of flutes left over.

Probably better to drill the shank clearance holes as deep as possible,
minimizing the depth of the tiny hole. There is a LOT of shank available
(1.31") on these drills.

Now that I think of it even on the 1/8 shank micro drills most the have
enough extra shank in front of the depth collar. If I gotta back drill it
anyway, might as well do it all at once.