Protrusion-Head Height Gages


Flat Head Protrusion

(also called flushness) – The distance the top of a flat head screw extends above the mouth of a specified gaging hole diameter (F dimension in the illustration shown below). Head Height – the distance from the bottom of a screw head to its extreme highest point.

Head Height

The distance from the bottom of a screw head to its extreme highest point.
These gages are designed to measure the protrusion height of flat head screws and the head heights of non-flat head screws with accuracy and speed. The protrusion heights are measured by placing a flat head screw in the appropriate gaging hole and positioning it under the indicator foot for measurement after having “Zeroed” the indicator on the gaging plate surface. The foot is raised. The screw is placed in the “V”. The foot is rested on the screw’s head and the measurement is taken. These multipurpose gages can be used to measure all types of outside dimensions of fasteners such as head diameters, body diameters, thread major diameters, across flats and across corners of hex heads, washer diameters, and nut thicknesses.

Protrusion Heights are Available With the Following Gaging Plates:

  • ANSI/ASME 82 degree flat head plates: #2 through 3/8″
  • ANSI/ASME 100 degree flat head plates: #2 through 3/8″
  • ISO 90 degree metric flat head plates: M2 through M10
  • SEMsCHEK plates for measuring head heights and lengths of SEMS screws after assembly
These gages are ideally suited for use in manufacturing and final inspection applications. When ordering Protrusion-Height Gages, specify dial indicator (.001″ resolution) or electronic indicator (either .0005″ or .0001″ resolution) and the gaging plate you require. Gaging plates can be quickly changed on the same gage. The results of a long form Gage Repeatability and Reproducibility Study for the Protrusion-Height Gage was 8%.