Wolff-Wilborn Pencil Hardness Tester

The Inspector's Dur-O-Test is a pocket hardness tester. It meets DIN EN ISO 22557. It can perform hardness tests on both flat and curved surfaces.

The instrument consists of a sleeve with a pressure spring that can be bent to various tensions by using a slide. The spring acts on a tungsten carbide needle (1.0 mm / 0.04 in.) with its tip extending out of the sleeve. A locking screw fixes the slide, thus maintaining constant spring tension. Protect spring from fatigue, therefore, always set tension value at zero when not in use. Three pressure springs of varying strengths ranging from 0-20 N (0-2000g) are available to cover a large hardness range. Protect spring from fatigue, therefore, always set tension value at zero when not in use.

1. Place the top of the Dur-O-Test on the test surface and draw a line approx. 10mm (0.4 in.) long over a period of 1 second, maintaining sufficient pressure to keep the needle against the rod stop.
2. If the tension has been too high the surface will be clearly marked.
3. If too low, there will be no mark. The correct tension will result in a barely visible mark.
4. Three interchangeable springs of varying strengths correspond to the test ranges engraved on the barrel:
   • No. 1 of 0 - 300 gms, each div. = 10 gms (Silver Spring)
     
   • No. 2 of 0 - 1000 gms, each div. = 50 gms (Red Spring)
     
   • No. 3 of 0 - 2000 gms, each div. = 100 gms (Blue Spring)