The Starrett 687 Series reads the large diameter of an 82° countersink directly, in .002" increments. Unlike a chamfer gage, which seats on the top edge of the chamfer, a countersink gage seats on the angular face — so it measures the countersink the way the print specifies it and the way a fastener will actually sit in it.

Why 82°

82° is the standard included angle for inch flat-head screws, which makes the 687 the countersink gage for most imperial fastener work. Starrett offers the same gage in 90° and 100° so the cone matches the countersink being inspected — the angle is not adjustable, and using the wrong angle gives a wrong diameter.

How It Reads

A set master ring is furnished with each gage for calibration and setting. Press the button on top of the indicator to firmly depress the gage head into the countersink; when the gage is lifted out, the reading is held until the reset button is activated. That hold makes the gage practical one-handed at the machine, where reading the dial in position is often impossible.

Choosing a Range

Four inch-reading ranges cover .020-.170", .160-.360", .360-.560" and .560-.780". Select the range that brackets the countersink's large diameter.

Applications

Aerospace and sheet-metal flush-fastener inspection, riveted assembly qualification, machined countersink verification, incoming and in-process inspection.