Basic information about indenter & dressers

Rockwell hardness (HR), Rockwell indenter

The Rockwell hardness test is characterized by the fact that the indenter is first pressed into the test material with a reference load (initial test force), which makes it possible to ignore the oxide film and unevenness of the material surface to some extent.
After the reference load is applied, the material is further pressed under the test load (full test force) and then returned from the test load to the reference load. Of the indentation obtained by the test load, the plastic deformation depth remaining after elastic recovery is obtained, and the difference from the depth obtained by the initial reference load is the hardness value of the material.
The hardness measured with the reference load of 10 kgf is called Rockwell hardness and that with the reference load of 3 kgf is called Rockwell superficial hardness.
The Rockwell hardness is defined as 1 when 2 μm depth is obtained and the Rockwell superficial hardness as 1 when 1 μm depth is obtained. The Rockwell hardness is denoted by the HR + scale symbol.

A Rockwell diamond indenter with 120° and a 0.2R conical tip is available in C scale (150 kg test load) and A scale (60 kg test load), and also includes the one for superficial hardness. Even if the shape is the same, the hardness is greatly affected by the round tip's accuracy and shape. Therefore, the hardness obtained by the A scale and superficial indenters is adjusted through higher accuracy processing than that used for the C scale indenter.

Scale

Scale is a test condition in which the type of indenter, reference load, and test load used for measurement are specified. In addition to the diamond indenter, there are four other types of steel ball indenters for Rockwell hardness testing, depending on their diameter.
In addition, for the loading device of the testing machine, one can select 6 different loads, and there are 30 different test conditions, called scales, in combination with 5 different indenters and 6 different test loads.
When, of the 30 scales, 15 scales with a reference load of 10 kgf are used to obtain hardness, it is called Rockwell hardness. Hardness obtained by 15 scales with a reference load of 3 kgf is called Rockwell superficial hardness. The applicable scale is conventionally determined for each test material.

Diamond indenters are to be used in a total of 6 scales: A, D, and C scales for Rockwell hardness, and 15N, 30N, and 45N scales for superficial hardness.

Vickers hardness (HV), Vickers indenter

A square pyramidal diamond indenter is pressed in and the surface area is calculated from the length of the diagonal line. Hardness is defined by this calculated area. Since the indentation is small, small or thin objects can be measured. It is suitable for measuring hardness distribution such as the depth of quenching.

The Vickers indenter has a square pyramid shape with a face angle of 136°±30′ of the tip diamond, and the micro-Vickers has the same shape.

Triangular pyramid indenters (also called Berkovich indenters or nanoindenters, or indenters for ultramicro hardness testing) are used to measure the hardness of thin films, Young's modulus, and nano-size indentation that cannot be measured with micro-Vickers.

Knoop hardness (HK), Knoop indenter

This is one of the indentation hardness. A diamond indenter with a rhombic shape is pressed in and the projected area of the indentation is used as the hardness. Since the indentation depth is shallower than that of a Vickers indenter and the indenter's penetration depth is also shallower, it is suitable for measuring thin objects, surface films, and objects such as glass that are difficult to measure due to chipping if penetrated deeply.

The Knoop indenter has rhombic square pyramid faces with dihedral angles of 172°05′ and 130°.

Indentation of Knoop indenter

Shore hardness (HS), Shore hammer

This is one of the rebound hardness. A steel hammer with a hemispherical diamond embedded in the tip is dropped from a certain height, and the height of the rebound is used as the hardness value. There are two types of testers: the C-type tester, which takes readings by the naked eye, and the D-type tester, which takes readings with a dial gauge. The D-type tester is compact, lightweight, and portable, and can be used to measure large parts, rolling rolls, railroad rails, and other large products directly on site.

We manufacture a variety of hammers based on C hammers for Shore C-type testers and D hammers for Shore D-type testers.

Brinell hardness

A load is applied with an indenter of steel or cemented carbide balls, and the hardness is obtained by dividing the load by the surface area of the indentation.
Since the indentation is larger than in other hardness tests, it is possible to measure the average hardness of the test material, making it suitable for materials that are not uniform in hardness.

Single-point diamond dresser

The single-point diamond dresser has a diamond with a protruding edge at the tip.
The approximate size of the diamond for the dresser is determined by the specifications (abrasive grain type, grain size, binding degree, and binder) of the grinding wheel to be dressed and the wheel dimensions (diameter and width).

The depth of cut should be 0.015 mm or less for finishing dressings and 0.04 mm or less for rough dressings, and large cuts at one time should be avoided if possible.

Approximate diameter and width of grinding wheel and reference size of diamond