Scratch hardness tester Model 293

manualportablefor plastics

Short description
Pencil hardness according to Wolf‑Wilborn, including 17 pencils (6B–9H). Three selectable test forces: 5 N / 7.5 N / 10 N.

Technical description
The TriForcePencil 293 simplifies carrying out the pencil hardness test according to Wolf‑Wilborn and ensures the prescribed test force and test angle. The guide is ergonomic and eliminates manual influence on the applied load. The weight block is fitted with three pencil holders that apply the correct test force to the pencil tip by a lever principle. The pencil protrusion is set via a rotatable adjustment screw with a distance tip. Recessed grip shells on the wheel covers provide secure handling when sliding the device over the surface under test. The scratch hardness tester is supplied in a plastic case.

Purpose and application
The pencil method belongs to the group of scratch hardness determinations. It is a simple and fast method for testing surface resistance to scratching and sharp‑edge abrasion. The method can be used during production processes, e.g. on roll‑to‑roll coating lines. The availability of three test forces (5 N / 7.5 N / 10 N) offers additional variation compared with devices that provide only one test force.

Test principle
Pencils of different hardness grades are drawn over the test surface at an angle of 45° with a chosen force of 5 N, 7.5 N or 10 N (± 0.1 N). The pencil hardness is defined by the two pencils used where the softer pencil still writes on the surface while the next harder pencil produces a perceptible groove.

Test procedure (steps)

• Retract the wood casing by approx. 5 mm so that the graphite core protrudes about 5 mm; use the special sharpener.
• Sharpen the graphite core to a sharp edge on 400‑grit sandpaper, keeping the pencil vertical.
• Place the TriForcePencil 293 on a flat surface and remove the locking screw.
• Turn the adjustment screw with distance tip downward to set the height distance (10 mm).
• Insert the prepared pencil into the holder for the selected force range.
• Insert the locking screw to fix the pencil; retract the adjustment screw.
• Set the device so the wheels contact the surface first, then the pencil tip; slowly slide the device (approx. 10 cm/s) in the direction of the pencil tip.

Notes
Differentiate between mere surface marking and actual penetration; use a damp sponge or soft eraser for verification if required. The appropriate pencil hardness must be determined empirically; start with a medium‑soft/medium type. Highly pigmented coatings with scaly pigments are less suitable for this test.

Reference class / certificate
Model 293 is supplied with a manufacturer test certificate M (factory calibration). The certificate contains, among other items:

• Nominal and actual value of the applied weight (test load)
• Test equipment used with calibration status
• Product identification
• Date
• Name of the tester

Scope of delivery

• Scratch hardness tester TriForcePencil 293
• 17 standard pencils (hardness grades 6B to 9H)
• 1 special sharpener
• 1 sheet of sandpaper
• Plastic case

Characteristics / technical specifications

• Drive: Manual
• Test force: 5–10 N (selectable 5 N / 7.5 N / 10 N; ± 0.1 N)
• Portable / stationary: Portable
• Scope of delivery: 17 standard pencils (6B–9H), special sharpener, 1 sheet of sandpaper, plastic case