Scratch hardness tester Model 318

manualportablehandheld

Short description
The Hardness Test Pencil Model 318 is used to assess the scratch resistance of surface protective layers and to measure the hardness grades of paints, plastic coatings and similar surface finishes. Small-sized, portable and ready to use for flat or curved surfaces. Four different test probes are available (sold separately). Three force ranges, up to 20 N.

Technical description
The Models 318 / 318S / 318 C are designed to measure the hardness of surface protective layers. These testers allow quick and easy quality control of surface protection layers even during production. Developed originally by Robert Bosch GmbH and manufactured by ERICHSEN, the devices enable determination, documentation and communication of hardness degrees as numerical values.

Test procedure using test tips No. 1, 2 and 3
The handling of the Hardness Test Pencil is simple: set the estimated or known spring tension with the slider. Hold the instrument upright and place its point on the test surface, then draw a 5 to 10 mm long line at approx. 10 mm/s. The stylus should produce a scratch just visible to the naked eye. If the spring pressure is too high the scratch is clearly visible; if too low no scratch appears. The applied pressure, fixed by locking the slider, is marked in Newtons.

Pressure ranges (three engraved scales)

• 0 - 3 N (blue marked)
• 0 - 10 N (red marked)
• 0 - 20 N (yellow marked)

The springs for each pressure range are colour coded and the corresponding scale is marked in the same colour.

Notes on guidance and test head
A sensitive guidance of the test pencil is required for useful results. Excessive pressure or a test head with an insufficiently smooth edge may produce traces that falsify results or complicate interpretation. Imitations with rough edges can cause unreliable results.

Test procedure using test tip No. 4
Test tip No. 4 (Opel, 0.5 mm dia.) has a special tip geometry and a length approx. 15 mm longer than the other marking pins. To ensure the preset test force, the test tip must be pressed into the test pencil by approx. 5 mm during the test.

Standards

• DIN 55 656
• Van Laar
• Bosch
• ISO 1518
• Opel

Technical data

• Drive: Manual
• Diameter: 16 mm
• Weight, net: approx. 250 g
• Total length: 160 mm
• Testing Force: 0-20 N
• Test tip no. 4: spring steel, with special tip geometry
• Scratch profile: Van Laar, Bosch, ISO, Opel
• Compression Springs: spring steel
• Portable / Stationary: Portable
• Test tips no. 1, no. 2, no. 3: tungsten carbide spheres

Accessories (examples)
Test tips (No. 1, No. 2, No. 3, No. 4), additional springs for each force range, chucking adapter (rolling), carrying/handling accessories and calibration certificates are available separately.

Characteristics / specifications

• Model designation: Model 318
• Manufacturer: ERICHSEN
• Testing force range: 0 - 20 N (three selectable ranges: 0-3 N, 0-10 N, 0-20 N)
• Diameter: 16 mm
• Total length: 160 mm
• Net weight: approx. 250 g
• Test tip materials: tungsten carbide spheres (tips No. 1–3); spring steel with special geometry (tip No. 4)
• Compression springs: spring steel (colour coded for ranges)
• Portable: yes
• Standards referenced: DIN 55 656, Van Laar, Bosch, ISO 1518, Opel