SEAT CUTTER NOTES:

The seat cutter is a special tool with 2 sets of cutting teeth, each
will do a different operation.
The inner cutter will cut a countersink for the flange of the insert.
The outter cutter will cut a new seat for the spark plug washer.
As illustrated in the picture we need the outter cutter to clean the
surface of the head 360 degrees.

Good SeatComplete	Bad Seat 1/2 incomplete

You do not have to go very deep with the
outter cutter just enough to clean the entire surface.
The outter cutter will actually set the depth of the inner cutter so that
the spark plug insert will be just below the surface for washer seat
applications.
Taper Seat Spark Plug Applications:
The operation is the same for taper seat inserts. We still use
the same procedure to get the correct depth for the insert flange.
Another interesting note about taper seat inserts is that they will
actually stick up slightly because we use a larger diameter on the flange
to purposely create a seal on the top of the flange on taper seat inserts.