Device and thread gauging method for ensuring spark plug orientation

A method of operating a measurement device to check an internal thread of a spark plug bore of a cylinder head for proper orientation of a spark plug in the cylinder head, the method comprising:

• positioning the cylinder head relative to the measurement device;
• setting an intersection of a plane of a seat surface and an axis of the bore as a coordinate origin of the measurement device, the seat surface being a surface configured to seat the spark plug within the spark plug bore;
• measuring x, y, and z coordinates for a first location, the first location corresponding to a major or minor diameter of a threadform of the internal thread;
• determining a pitch of the internal thread;
• calculating a thread start location based on the x, y, and z coordinates of the first location and the pitch of the internal thread, the thread start location being a location where the major or minor diameter of the internal thread intersects the seat surface;
• comparing the thread start location to a reference location;
• and
• outputting a result of the comparison of the thread start location to the reference location.

A thread gauging device comprising:

• a support surface configured to support a cylinder head;
• a probe configured to be received in a spark plug bore of the cylinder head and detect characteristics of the spark plug bore;
• a base attached to the probe and configured to move the probe relative to the cylinder head;
• a display;
• and
• a control module in communication with the base, the probe and the display, the control module being configured to send control signals to the base to control movement of the probe relative to the cylinder head, the control module being configured to receive signals from the probe indicative of the characteristics of the spark plug bore, the control module being configured to move the probe to measure a z position of a seat surface of the spark plug bore, the control module being configured to move the probe to measure at least one set of coordinates, each set of coordinates being at a major or minor diameter of a corresponding threadform of an internal thread within the spark plug bore, the control module being configured to determine a pitch of the internal thread and calculate a thread start location where the major or minor diameter of the internal thread intersects the seat surface based on the coordinates of the at least one set of coordinates, the pitch of the internal thread, and the z position of the seat surface, the control module being configured to compare the thread start location to a reference location, the control module being configured to operate the display to output a result of the comparison of the thread start location to the reference location.