Counter Sink Tool
                          Ted Edwards

See also: C_Sinker1.jpg, C_Sinker2.jpg and C_Sinker3.jpg

I picked up a few of these tools in various sizes and shapes from Boeing
Surplus along with an assortment of bits.  The brand name on the one 
pictured is MAGNAVON (not MAGNAVOX).

The device is spring loaded to retract the cutter and is shown thus in 
C_Sinker1.jpg.  The shaft is to be chucked in a drill press or hand 
drill.

The pilot is inserted into the screw/rivet/whatever hole, the base 
set against the surface and the drill turned on.  The outer case does 
not rotate but the cutter can be pressed into the work to the selected 
amount of depth.  This is adjusted by retracting the splined 
colar and turning the base.  C_Sinker2.jpg shows the device extended 
as it happens to be adjusted.

Many interchangeable cutters are available or can be made.  Two 
additional cutters are shown in C_Sinker3.jpg.

These are very verasatile tools.  I have used them for counter sinking 
1/16" flat head rivets, #14 wood screws and, just yesterday for combined
counter sinking and counter boring phenolic to accept recessed #10 
stainless wood screws for a boat related electrical project.

These tools are very quick to use and can gaurantee a number of holes 
countersunk to identical depth.

It wouldn't be hard to make (or modify) a bit for the rounded edge holes
the armour maker was looking for.