P,


You may want to check out "trepanning".
Trepanning is a machining method of producing larger diameter, deep
drilled holes which can be more cost effective than typical gundrilling
techniques.  It is best described as core drilling.  Unlike gundrilling,
Trepanning leaves a core from the center of the bar instead of turning it
all into chips.


One vendor, easily found with a Google search is:

Trepanning Specialties, Inc.
16201 Illinois Ave., Paramount, CA 90723
Voice (562) 633-8110 . FAX (562) 633-0141
More than likely... many others.

Jack Beale

According to Google this is a methods of drilling holes
in skulls.

Paul Lamar


True Paul,
But it it also cutting a slot at a diameter without a center. A hole saw is
multi-tooth trepanning.
Bill Jepson


I contact the company and to get a 4 inch core OD out of the center they
would have to start with 13 inch OD. Where are you going to find
13 inch OD ??? :)

and it would cost about $120 dollars.

Paul Lamar