Simple, portable instrument for testing the hardness of materials acc. to ASTM D2583. Originally called the Barber-Colman Impressor, the Barcol impressor was developed by Walter Colman as a hand-held, portable means of assessing the hardness of a material during World War II. The United States Army Air Corps required a hand-held method of checking the hardness of rivets due to concerns that aircraft could be sabotaged by replacing normal rivets with soft lead or wooden ones which would fail during flight. The impressor operates when the tip is pressed against the material in question. The hardness of the material determines how far the tip indents and this is transferred by a tension spring and lever to be read on a dial.
The Barcol hardness test is generally used on soft materials such as rigid plastics. It measures hardness based on indentation of a sharp point with a flat tip. The test is performed using a similar method and indentation device as that used to measure Shore D hardness however the Shore D indenter has a round tip. Barcol hardness is not a valid hardness measure for curved surfaces.
When pressure is applied to the device, a point penetrates the material and the degree of hardness is displayed on a dial, which is graduated from 0 to 100.
The Impressor is a convenient tool for testing the hardness of aluminum, aluminum alloys, copper, brass and other materials including plastics and fiberglass. The instrument is designed for use on fabricated parts and assemblies as well as on raw stock.
No experience required; can be used in any position and in any space that will allow for the operator’s hand. The hardness reading is instantly indicated on the dial, which is divided into one hundred graduations. No waiting, preloading or separate measurements.
The Impressor weighs only 1 lb. 2 oz. The entire Impressor package comes complete with carrying case, adjusting wrench and two spare indenter points. The Impressor + case = 2 lb. 8oz. Shipping weights = 4 pounds, box = 12 x 11 x 6 inches, dimensional weight 5 pounds. (1.8 kilograms, box = 21 x 28 x 16 cm, dimension weight 2.5 Kilograms)
The Impressor is best suited for testing homogeneous materials. Materials of granular, fibrous or coarse structure will produce a wide variation in hardness readings because of the small diameter of the indenter point.
For accurate readings, material should be at least 1 /32″thick and large enough for a minimum distance of 1/8″ in any direction from the indenter point to the edge of the specimen. The testing area should be smooth and free from mechanical damage.
Simply exert alight pressure against the instrument to drive the spring-loaded indenter point into the material. The indenter point must be perpendicular to the surface being tested. On very soft metals, the highest reading should be used since cold flow permits the spring loaded indenter point to continue penetration.
Note: Physical characteristics of very soft materials are such that uniform correlation between different hardness measuring systems cannot be established. We recommend that Impressor hardness limits for each material be established by test.
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