Elcometer 501 Pencil Hardness Tester
Using the same technique of evaluation with pencils as the Elcometer 3080, this instrument enables the pencil lead to be maintained at a constant force of 7.5N, and at the appropriate angle - which increases the reproducibility of the test.
The Elcometer 501 is supplied in a plastic carrying case and comes
complete with a set of pencils in each of the 14 hardnesses from 6B to 6H, two pencil sharpeners and a sandpaper block.
Also known as the Wolff-Wilborn test method.