Rockwell machines

An alternative to the measurement of the dimensions of the indentation by means of a microscope is the direct reading method, of which the Rockwell method is an example. The Rockwell hardness is based on indentation into the sample under the action of two consecutively applied loads - a minor load (initial) and a standardised major load (final). In order to eliminate zero error and possible surface effects due to roughness or scale, the initial or minor load is first applied and produce an initial indentation. The Rockwell hardness is based on the increment in the indentation depth produced by the major load over that produced by the minor load. Rockwell hardness scales are divided into a number of groups, each one of these corresponding to a specified penetrator and a specified value of the major load. The different combinations are designated by different subscripts used to express the Rockwell hardness number. Thus, when the test is performed with 150 kg load and a diamond cone indentor, the resulting hardness number is called the Rockwell C (Rc) hardness. If the applied load is 100 kg and the indentor used is a 1.58 mm diameter hardened steel ball, a Rockwell B (RB) hardness number is obtained. The facts that the dial has several scales and that different indentation tools can be filled, enable Rockwell machine to be used equally well for hard and soft materials and for small and thin specimens. Rockwell hardness number is dimensionless. The test is easy to carry out and rapidly accomplished. As a result it is used widely in industrial applications, particularly in quality situations. 

The shape is usually either a sphere (Brinell, and Rockwell B or C) a square pyramid with apex angle = 135° (Vickers) a trigonal pyramid (Berkovich) or an elongated four-sided pyramid (Knoop). (See Figure 1.2). For quality control in manufacturing operations, semi-automatic Rockwell machines, and their various indenters, are also useful. 

The Rockwell superficial test was developed to accommodate smaller and thinner samples than the standard Rockwell test. The test principle is identical to the standard Rockwell test but the major and minor loads are substantially smaller. The test machine is also similar but modified to accommodate the smaller loads. Dual purpose machines can handle both standard and superficial tests. 

Most laboratory and shop-use Rockwell hardness testers are nonportable, lever operated, deadweight machines. Newer versions have digital readouts rather than the traditional analogue dial. Some designs of Rockwell testers employ a spring-loading system instead of deadweights. 

Rockwell hardness testing has been extended to both low and high temperature regimes usually by enclosing the sample and part of the machine in an environmental chamber and using extensions for the anvil and indenter. 

Spherical rollers were machined from AISI 52100 steel, hardened to a Rockwell hardness of Rc 60 and manually polished with diamond paste to RMS surface roughness of 5 nm. Two glass disks with a different thickness of the silica spacer layer are used. For thin film colorimetric interferometry, a spacer layer about 190 nm thick is employed whereas FECO interferometry requires a thicker spacer layer, approximately 500 nm. In both cases, the layer was deposited by the reactive electron beam evaporation process and it covers the entire underside of the glass disk with the exception of a narrow radial strip. The refractive index of the spacer layer was determined by reflection spectroscopy and its value for a wavelength of 550 nm is 1.47. 

The hot-feed rubber extruder is usually characterised by a relatively large screw depth and a relatively short L/D ratio of the barrel of 3 to 8 1 with the greatest number of machines having a ratio of 4 1. The barrel comprises usually a cast iron outer with either a traditional replaceable nitride liner, or, in the case of one manufacturer, of a single piece construction with an integral cast liner which has a surface hardness of Rockwell C60-62 and a hardness depth of 1.5 mm. The functional life for the bimetallic barrels is longer than for conventional nitride liner systems. 

The Rockwell testing machine is thus a framework permitting stable support of the workpiece on one side and means to impress the indenter under specified load on the other. A dial indicator attached to the indenter spindle is used to read direcdy the depth of indentation in hardness numbers. 

Again there are examples from physical measurements that demonstrate how traceability can be achieved. There is no SI unit for hardness but there is a well-established traceability system for the results of hardness measurements. Hardness scales, e.g. Brunei or Rockwell, are defined in terms of the properties of the machines used to measure the hardness. The properties defined include the shape of the indenter, the applied load and the rate of application of the load together with the tolerances on the properties. Thus utilising a machine that meets these defined properties provides the traceability for the results obtained using it. However it is a difficult task to keep monitoring the properties of the machines and reference materials are used in the form of hardness blocks whose hardness has been measured at a standards laboratory on a machine with very well defined and monitored properties. 

TENSILE YIELD STRENGTH PSl HARDNESS AS MACHINED ROCKWELL AVAILABILITY OF CASE HARDNESS ROCKWELL O.D. WEAR RESIST. ROOT WEAR RESISTANCE CORROSION RESISTANCE MATERIAL AVAILABILITY EASE OF MACHINING APPROX. COST PER POUND ... 

Bimetallic cylinder n. In most modern extruders and injection machines, the barrel is lined, by centrifugal casting from the melt, with any of several white irons containing chromium and boron carbides and having hardnesses near Rockwell C65. Aster finish-grinding and polishing, the liner, about 1 mm thick, provides excellent resistance to wear or corrosion or both, depending on the formation. The best known trade name is XALOY . 

The first machine to use 30-cm tape fabricated weapon bay doors for the B1 bomber. A government contract hmited the expenditure by the prime contractor (Rockwell), but without any sacrifice in accuracy. Requirements were met by a manually operated machine with automatic width indexing, with other motions initiated by the operator. 

The tribological properties of Cu nanoparticles were determined on an MRS-lOA four-ball test machine at 1450 rpm in ambient conditions. The 12.7-mm-diame-ter balls used in the test were made of bearing steel (composition 0.95%-1.05% C, 0.15%-0.35% Si, 0.24%-0.40% Mn, <0.027% P, <0.020% S, 1.30%-1.67% Cr, <0.30% Ni, and <0.025% Cu) with a Rockwell hardness (Rc) of 61-64. The base oil was chemically pure liquid paraffin (LP), which has a distillation range of 180°C-250°C and density of 0.835-0.855 g/cm. Before each test, the balls and specimen holders were ultrasonically cleaned in petroleum ether (normal alkane with a boiling point of 60°C-90°C) and then dried in hot air. At the end of each test, the wear-scar diameters (WSD) of the three lower balls were measured on a digitalreading microscope to an accuracy of 0.01 mm. Then the average wear-scar diameter from the three balls was calculated. 

We are unaware of any clear correlation between measured physical properties, such as glass transition temperature or impact strength, and the practical machinability of a polymer. Polymeric hemishells have been produced by single-point diamond machining of partially cross-linked polystyrene. We obtained a sample of this polymer from Rockwell International, Rocky Flats, Colo, where the micromachining was to be performed, to serve as a basis for comparison with the various copolymers we produced. We devised a simple method for qualitatively assessing machinability which involves the following ... 

The microscopic "tool marks" thus produced were examined for smoothness and evenness as compared with the machinable sample supplied by Rockwell. 

Samples of polymers which appeared to be most machinable were supplied to Rockwell. Fig. 3 is a SEM photomicrograph of a hemi-shell produced from a copolymer of triphenyl-p-styryl lead and octadecyl methacrylate, which was the most machinable of the lead-containing copolymers studied. Reactivity ratios were measured for these two monomers using IR spectra of copolymers of varying compositions polymerized to low conversions. The values were calculated to be Rp 1.05 and 0.396. This indicates that... 

In order to quantify the fracture energy for such a coating, a test that causes the coating to fail by the same mechanism is required. This can be accomplished using an indentation test, which was first developed for bilayer systems [17]. The test consists of indenting the TBC system with a Brale-type conical indenter (a Rockwell hardness tester or mechanical testing machine can be used for this purpose) [18, 19]. 

The material reportedly used for the most tooling has been a machinable grade of heat treated tool steel having a hardness of 34-42 on the Rockwell C scale. Since there is no metal-to-metal tool closure, close tolerances, or sophisticated cooling, the tooling costs are estimated to be about one-third of their counterparts for injection molding. 

HMI human machine interface HMW-HDPE high molecular weight-high density polyethylene H2O water H-P Hagen-Poiseuille HPLC high pressure liquid chromatography HPM hot pressure molding HRC hardness Rockwell C (C scale)... 

Hardness is a measurement of material resistance to plastic deformation in most cases. It is a simple nondestructive technique to test material indentation resistance, scratch resistance, wear resistance, or machinability. Hardness testing can be conducted by various methods, and it has long been used in analyzing part mechanical properties. In reverse engineering, this test is also widely used to check the material heat treatment condition and strength, particularly for a noncritical part, to save costs. The hardness of a material is usually quantitatively represented by a hardness number in various scales. The most utilized scales are Brinell, Rockwell, and Vickers for bulk hardness measurements. Knoop, Vickers microhardness, and other microhardness scales are used for very small area hardness measurements. Rockwell superficial and Shore scleroscope tests are used for surface hardness measurements. Surface hardness can also be measured on a nanoscale today. 

Biased data from measurements might result from uncalibrated instruments. For example, a biased Rockwell hardness tester with a misalignment might constantly produce lower hardness values. It is usually required to check the tester with a standard test block to ensure that the hardness test machine is functioning properly before collecting any test data. Figure 6.6 shows the ASTM hardness test standards for Rockwell hardness testers manufactured by Instron Corporation. 

There are two aspects of reliability in reverse engineering. Reliability in statistics refers to the consistency or repeatability of a measurement. It relies on the repeatability of the same measurement instrument, and the comparability of similar measurement instruments. It also depends on the repeatability of the operator of the test machine or the device. It does not imply the validity of the data that reflect whether the test result or measurement is what was intended to be obtained. A misaligned Rockwell hardness tester will repeatedly produce consistently biased hardness data. Statistically, the measurement by this tester is of high reliability despite it is not producing valid engineering data. 

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