M14x1.25 Spark plug Seat Cutter washer seat detail.
The M14x1.25 Seat Cutter total diameter is Approx. .745 inches or 18.9mm yours may differ on older versions. If you see this diameter cut into the head this step is complete!
If you are unsure if the Outer diameter of your seat cutter is touching, mark one of the outer teeth with a black ink pen to see if it touches the base material of the head. The ink mark will be removed if it is touching the head.
Before using the seat cutter be sure the tap is approx. 1/4″ or 6mm below the surface. This will help ensure the cutting teeth on the seat cutter do not touch the back of the tap flutes.
Note: When turning the seat cutter approximately 20 full turns inspect the seat it may be fully cut and cleaned up at this point. You do not want to go very deep just enough to clean the seat. After the Seat Cutter is used you should see this washer seat diameter of .745 inches or 18.9mm cut into your spark plug hole and the head is ready to receive the insert. The Internal Counterbore has also cut out the first few threads for the flange of the insert. Oil the install driver tool with driver oil or 30wt motor oil then screw the insert onto the driver. The insert should easily screw in flush to the surface by hand before using the force from the insert driver tool. As the driver starts to cold roll the bottom few threads of the insert you may notice a little more resistance, continue a few more turns as the driver slightly passes through the bottom of the insert. Repair is complete at this time remove driver.
