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Vickers Hardness Testing Machine

 

The Vickers Pyramid Hardness Testing Machine was designed and developed by the Vickers company to be the standard instrument to perform the Vickers Hardness Test. It is testimony to its design and construction that so many of them are still in use today in the worlds' most successful automotive and aerospace companies.

UK Calibrations have the only original Vickers service engineers operating anywhere in the world. and are uniquely placed to provide the best maintenance, support and calibration service available.

This article covers the Vickers Pyramid Hardness Testing Machine (also known as the model VHTM 2000) as built by Vickers Ltd. Engineering Group, Container and package machinery division, Vickers-Armstrongs Crayford works in Kent.

The model shown here was fitted with a dynascope in place of the original microscope. This was also fitted with a Veeder Root measuring device which allowed the readings to be converted into HV by a DRO (a Digital Read Out) and later the PC based CRO (Computer Read Out)

 

The Vickers Hardness Test

The Vickers hardness test was developed in 1924 by Smith and Sandland. The test evaluates hardness in a manner similar to Brinell taking the ratio between the load applied and the surface area of the resulting impression.

It was decided that the indenter shape should be one based on the following :-
  • to be capable of producing geometrically similar impressions, irrespective of size
  • the resulting impression should have well defined points of measurement
  • the indenter should have high resistance to self deformation.

A diamond in the form of a square based pyramid satisfied these conditions. It had been established that the ideal size of a Brinell impression was 3/8 of the ball diameter. As two tangents to the circle at the ends of a chord 3d/8 long, intersect at 136 degrees It was decided to use this as the included angle of the indenter. The angle was varied experimentally and it was found that the hardness value obtained on a homogeneous piece of material remained constant, irrespective of load.

The unit of hardness given by the test is the Vickers Pyramid Number (HV). The Vickers Pyramid Number (HV) is determined by the ratio Force (applied to the Indenter) divided by the Area (the surface area of the resulting indentation).

The Vickers hardness test gained popularity as it is often easier to use than other hardness tests since the required calculations are independent of the size of the indenter, and the indenter can be used for all materials irrespective of hardness. The Vickers test can be used for all metals and some ceramics and has one of the widest scales among hardness tests.


The Vickers Hardness Machine (VHTM)

As mentioned in the introduction, the Vickers Pyramid Hardness Testing Machine was designed and developed by the Vickers company to be the standard instrument to perform the Vickers Hardness Test. It was built to be a scientific instrument, using machine tool principles and capable of both workshop and laboratory application. Indeed many of these machines are situated in dirty, dusty, foundry environments, and thanks to their dust-proof construction, survive and give good service.

The original Vickers Pyramid Hardness Testing Machine had many optional extras including Low tables for very large pieces, and a special mount to indent gear teeth. There was even an accumulator option for machines without access to ac mains.

We have scanned some of the original manuals and they are available here for you to download. The Vickers HTM catalogue and instructions booklet is a general introduction to the Vickers Pyramid Hardness Testing Machine and the available options and gives brief operating instructions. The working instructions for Vickers HTM is a much more in-depth document, covering the unpacking and setting up of the machine as well as detailed instruction on usage.

We pride ourselves on being the best source of advice and service on the Vickers Pyramid Hardness Testing Machine, anywhere in the world, and are always happy to talk to you about your machine and its requirements.


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