Name: Scratch Adhesion Mar Tester
Price: 2168.0 USD
Availability: InStock

Features

The basic concepts of the original Hoffman instrument have now been engineered into a much more useful instrument
Stylus of the exact contour, both loop and needle, developed for the Balanced Beam Tester are now used in the S.A.M. Tester
The advantages are greater sensitivity in the lower loading range on the stylus and portability with ease of use in any position and under most any conditions. (Note: load on the stylus is limited to 2,500 grams.)
Load on the laboratory model instrument may be increased to 10,500 grams.
It is only 5 inches long, 2 inches high and, excluding the control dial and locking nut, is less than 0.67 inch thick.
Truly portable and can be used in any position
The instrument body is machined from solid nylon to prevent marring of the test material surface and results in a weight of less than 5.5 ounces
Performs test like: Scratch Resistance, Mar Resistance, Adhesion with Gardco/Hoffman Cutter, Adhesion with Cross Cutters, Hardness, Degree of Curer, Continuously Variable Load From 20 To 250 Grams or From 200 To 2500 Grams

More Information

Original Hoffman Tester Concept - The Hoffman Tester is one of the “old line” developments in the paint industry and comes as close as any instrument to date of being “The Paint Chemist’s Educated Knife”. The “blade” of the original Hoffman instrument is made of hardened tool steel, is cylindrical in shape, with the axis of the cylinder held at 45 degrees by a beam carrying a sliding weight. The beam is attached through a hinge arrangement to a small four wheel trolley. Sufficient downward force on the trolley lifts the weight which imposes a force on the cutter against the test specimen in proportion to the positioning of the weight on the beam. The trolley is then pulled across the test sample and the effect, if any, of the “blade” is observed.

The Hoffman Tester when used in the lower range of up to 250 grams loading has been used for determining scratch resistance of a surface and is so listed in STP 500, 5.1.2.5, Paint Testing Manual, published by the ASTM. In this lower range it has also been used for evaluating mar resistance as also listed in STP 500, 5.1.6.1.4. It has had its greatest application, however, in the high range, up to 2500 grams, for cutting completely through the coating to the support surface for measuring properties such as degree of cure and adhesion. Information on its use in measuring adhesion is contained in STP 500, 5.3.4.8.

A major advantage of the cylindrical “blade” used in the original Hoffman instrument is that by a slight rotation, a fresh cutting edge is exposed for use. A major disadvantage is that the “blade” loading is by gravity which dictates that the instrument may be used in the horizontal position only and this adds to the disadvantage of having to accommodate a relatively long weight beam under steady conditions while moving the trolley across the test surface.

Scrape Adhesion and Mar Testing Concept - The most widely used instrument for evaluating coatings for scratch adhesion and mar resistance is the Balanced Beam Tester. Stylus of the exact contour, both loop and needle, developed for the Balanced Beam Tester are now used in the S.A.M. Tester. The advantages are greater sensitivity in the lower loading range on the stylus and portability with ease of use in any position and under most any conditions. (Note: load on the stylus is limited to 2,500 grams.) Load on the laboratory model instrument may be increased to 10,500 grams.

Crosscut Adhesion Testing Concept - Three of the largest variables in measuring adhesion with a multi-tooth cutter as prescribed in ASTM standard D3359, Method B, are now brought under control by the use of the S.A.M. Gardco Instrument Loading Handle.

The load that is imposed on the cutter.
The uniformity of load across the width of the cutter.
The angular relationship of the cutter to the test surface.

In addition, an extended life of the cutters will be experienced under most conditions as excessive load on the cutter is largely eliminated. For consistent results, the downward force on the adhesion cutter must be just enough to cut through the test material. If complete penetration is not obtained throughout the cross cut pattern, the individual squares within the pattern are not isolated and erroneous results will be obtained. If too much force is applied, the tips of the cutter teeth penetrate the supporting base resulting in a decrease in area of the squares in the cross-hatch pattern. For example, with a 1mm cutter tooth spacing, the individual squares have an area of 1 sq mm or 0.00155 sq. in. Each of the teeth in the cutter have an included angle of roughly thirty degrees. Therefore, for each mil that the cutter teeth penetrate the base, the area of each square is reduced by about three percent.

Standards

ASTM D2197
ASTM D3359

Procedure

First insure that the instrument fulcrum is positioned for the required range, either 20 to 250 grams or 200 to 2500 grams and set the desired loading on the load control dial.
Place the lower edge of the instrument against the test surface with sufficient pressure to insure uniform contact.
While held in this position, draw the instrument in a direction away from the “blade”.
Observe the nature of the mark left by the “blade”, if any. The test may then be repeated at a different setting on the control dial.

Balance Beam Use

Prior to the use of the S.A.M. Tester fitted with the Balanced Beam stylus adapter, insure that the stylus of choice is installed and that the fulcrum is in the correct position for either the high or low range.
Set the desired loading on the stylus by loosening the locking nut and rotating the dial to the desired value.
Retighten the locking nut taking care not to change the set reading on the dial.
Hold the lower edge of the instrument against the test surface with enough force to overcome the loading on the stylus.
Retaining this force, move the instrument along the test surface in the direction at a rate of 0.5 to 1.0 inches per second.
If the coating is not damaged in the initial test, continue testing using successively higher loading on the stylus until the desired results of coating failure is observed.
Both the loop and the needle stylus are produced from 1/16 inch tool steel, heat treated to a hardness of Rockwell C 58 to 60 and then polished. The loop stylus has an outside radius of 0.128". The needle stylus has a 1.00mm diameter tip.
Warning: Do not interchange either the loop or needle stylus between the Balanced Beam Tester (Model 2197A) and the S.A.M. Tester. Overall length of the stylus for the Balanced Beam Tester (Model 2197A) is 1.000" with an extension beyond the fixture of 0.375". Overall length of the stylus for the S.A.M. Tester is 0.440" with an extension beyond the adapter of 0.190".

CrossCut Adhesion Use

Prior to use of the S.A.M. Tester fitted with the adhesion cutter attachment, insure that the cutter of choice is installed and that the fulcrum is in the correct position for either high or low range.
Set the desired loading on the cutter by loosening the locking nut and rotate the dial to the desired value.
Retighten the locking nut taking care not to change the set reading on the dial. Hold the lower edge of the instrument loading handle against the test surface with enough downward force to overcome the loading on the cutter.
Retaining this downward force, move the loading handle along the test surface making a trailing pattern with the cutter.
Repeat this cutting motion at 90 degrees to the first cut. (Note that the lower front surface of the instrument is undercut so as not to disturb the surface in the area of the first cut.)
Evaluate results obtained as prescribed in ASTM Standard D 3359, Method B.
Note: The cutter may be loaded in two different ranges: 20 to 250 grams and 200 to 2500 grams. If operating in the low range, divide the gram force required on the cutter by 10 and set the resultant value on the adjusting knob which has 25 divisions. If operating in the high range divide the required load by 100. It is most difficult when using the cutters in the standard handle to obtain uniform loading across the width of the cutter. Such uniform loading is required if reproducible results are to be obtained. The reasons are the same as given above for overall loading of the cutter. The adhesion cutter controller insures uniform loading from side to side of the cutter. The cutter attachment is secured to the lever arm of the controller by a single shoulder bolt and is free to rotate on this bolt. Therefore, the cutter is self aligning on the test surface. Also, for reproducible results, the face of the cutter must be held at 90 degrees to the test surface during its movement on such surface. An angle greater than this will cause the cutter to “ski” to the top of the coating while an angle less than this will cause the cutter to dig deeper.

Important Instructions for Changing Range of Tester

It is set to operate in the high range (200 to 2500 grams).
To set the handle to operate in the low range (20 to 250 grams), loosen the lock nut, set the control dial at minimum and retighten the lock nut.
Remove the Allen shoulder bolt from position “C” and place it in opening “B” while moving the cutter arm up and down for an easy fit.
Remove the shoulder bolt at position “A” and place it in the opening at “C”.
After setting the desired load on the control dial, the handle is ready for use in the low range.
Reverse this procedure to restore high range operation after setting the control dial at minimum.
(Caution: Do not remove the other shoulder bolts as interior components will drop out of place. Do not overtighten the shoulder bolts as the threads will be stripped from the nylon handle.)

Scratch Adhesion Mar Tester (S.A.M. Tester)

Scratch Adhesion Mar Tester