Hardness Test Pencil Model 318

Description

The Models 318/318S/318 C are used to measure the hardness of surface protective layers. The hardness grades of paints, plastic coatings, etc. are measured with these testers. Whether the surface is flat or curved, small or large, these small-sized testers are always ready to use and easy to transport. Anyone who is responsible for quality assurance will appreciate this advantage. The proper curing and constant hardness of the surface protection layer enable a smooth production process. Deviations result in rejects, production delays and complaints. Developed by Robert Bosch GmbH in Stuttgart and manufactured by ERICHSEN, these devices enable quick and easy quality control of surface protection layers – even during production.

Test Procedure using Test tips No. 1, 2 and 3

The handling of the Hardness Test Pencil is extremely simple. The estimated or known spring tension is set with the help of the slider. Holding the instrument upright and placing its point on the test surface one draws a 5 to 10 mm long line at a rate of approximately 10 mm/sec. The stylus should produce a scratch which is just visible with 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.

Three scales are engraved into the test pencil for the three pressure ranges:

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

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

A basic requirement to gain useful results is a sensitive guidance of the test pencil. If the pressure exerted onto the surface is too high, it is possible that the outer edge of the test head produces a trace falsifying the results or rendering their interpretation difficult.

Especially when using imitations with an edge of the test head that is not sufficiently smooth, this effect sometimes led to inappropriate scepticism with regard to the test method in general.

Test Procedure using Test tip No. 4

The test tip in accordance with "Opel" (0.5 mm dia.) has got a special tip geometry and a length that exceeds that of the other marking pins by approx. 15 mm. To ensure the desired test force, preset by the fixed slider’s position, working on the test tip, the latter must be pressed into the test pencil by approx. 5 mm during the test.

Scope of delivery

• Hardness Test Pencil, Model 318
• Test tip no. 1 (according to Bosch, 0.75 mm Ø)
• 3 springs (0 - 3 N; 0 - 10 N; 0 - 20 N)
• Plastic case
  
  

NEW – ERICHSEN SmartPen – The new generation of mobile scratch hardness testing

For the hardness measurement of surfaces, there are our since many years well-proven hardness test pencils, models 318 and 318 S as well as models 435 and 435 S, already well established across the branches. With these test devices, the degrees of hardness of paint films, plastic coatings, etc. can be determined, named, documented and communicated in numerical values. No matter whether on a flat or curved surface, small or large, the instrument is always ready for use and, because of it’s small size, easy transportable. With the ERICHSEN SmartPen, a modular hardness test pencil with digital test force setting and display (resolution 0.05 N) is now available.