On Wed, 21 Aug 2013 08:42:49 -0400, Joe AutoDrill
wrote:

On 8/21/2013 8:34 AM, Ed Huntress wrote:
With ductile iron, machineability depends heavily on hardness (this
sounds like a soft casting, though) and the level of free, dispersed
carbides. Trying to get too delicate with drill bits is not likely to
give good results. Something like a Racon point may be the trick, but
I'm sure there is experience-based data on drilling the stuff, which
is a lot better than guessing.

The guy is making thru holes which will then be manually cut into slots
in a future operation. I doubt "good results" for this particular
customer actually has much more meaning than "a hole in roughly the
right place" but I still need the stability for the machine as we build
for thrust, but side load.

Hmm. It sounds like an interesting workpiece. Do you know what it's
for?

I don't know if you caught this, but I'm now chief editor of Fab Shop
Magazine Direct. Any fabrication jobs you encounter could be
interesting to me -- and with possible promotion value for you. g

--
Ed Huntress