Tim-

I use a method very similar to Mr. Velander with good results
(ie, no calls from the Fab CAM operators). My Fab drawing is
added to the Drill Drawing Layer so as to be included with the
Drill Size listing, and is included with all jobs.

A few notes:
1- Explicitly call out all hole sizes used as mechanical markers
as "Marker hole for Slots. Slots are xxMil wide NPT (or Plated).
Hole center marks center of xxMil too used to rout slot."

2- If a fairly large routing tool is to be used, be sure to locate marker 
holes with an offset toward the center of the desired cutout to
accommodate the radius of the tool and the clearance radius at the
corner. This can be calculated from the tool diameter. If space is tight,
you can request that the majority of the cutout be routed with say
a 100Mil tool, and specify that the corners are to be routed to a smaller
specified radius using say a 20 or 30Mil finish rout. This is far faster 
for the fab house.

3- I draw and dimension each cutout and notch explicitly on the Drill
Drawing Layer to exactly indicate the desired feature. This is good
backup info when using a multiplicity of marker hole sizes, as Protel
isn't the greatest for checking hole sizes by selection. Some fab
CAM operators prefer to work only from the dimensional drawing
info only, as it allows them great freedom in tool and path selection.

4) Don't assume the fab house can't or won't drill a 1Mil hole. I had
a call from an offshore house telling me that Laser-drilling the 1, 2,
and 3Mil holes would take an extra day or two! I find a good rule
of thumb is to specify _everything_, with wide but fixed tolerances 
for "don't care" items. The old USSR had the right idea: "Anything
not Required is Forbidden"!

Brian

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