Barcol hardness test 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
Roll hardness tester of the movement, the pawl spring releases the hammer mass. The impact spring contracts causing the hammer mass to strike against the plunger. This is the impact. The hammer mass then rebounds back to the body of the hammer and distance travelled is recorded on the scale. The rebound distance depends directly on the hardness of the roll under test: A softer roll will absorb more of the impact energy and the rebound distance will be less. A harder roll will reflect more of the impact energy and the rebound distance will increase. Roll hardness is one of the most