Engineer's blue

Last updated

Engineer's blue (also known as scraping blue, Prussian blue, or simply bluing) is a highly pigmented paste used to assist in the mating of two or more components.

Contents

History

Joseph Whitworth popularized the first practical method of making accurate flat surfaces, during the 1830s, by using engineer's blue and scraping techniques on three trial surfaces. Prior to his scraping technique, the same three plate method was employed using polishing techniques, giving less accurate results. This improvement led to an explosion of development of precision instruments using these flat surface generation techniques as a basis for further construction of precise shapes.

Preparation

Engineer's blue is prepared by mixing Prussian blue with a non-drying oily material (for example, grease). The coloured oil is rubbed onto a reference surface, and the workpiece is then rubbed against the coloured reference; the transfer (by contact) of the pigment indicates the position of high spots on the workpiece or conversely highlight low points. [1] This method has been used to test the flatness of surfaces and the trueness of a bearing assembly.

The fitter may be told to "blue it up" when using this piece of equipment.

Use in toolmaking

Prussian blue is widely used by tool makers when the core and cavity of a mould is matched during final assembly. It is also used in other tooling applications, especially during assembly, such as stamping tools and pressure die casting tools. A thin coating of Prussian blue is applied (usually with a paint brush) on the "insert", regardless of the shape or contour of the mould or tool before the matching is done with the mating part. If the Prussian blue (generally called just "blue") appears evenly on the mating area, it is considered, by the tool makers, as "good matching", indicating a good final product from the tool. Usually no tool would be transferred to testing or production without "blue matching", (a term generally used by tool makers in Asia). Prussian blue is considered as an integral part of precision tool making.

Related Research Articles

<span class="mw-page-title-main">Lathe</span> Machine tool which rotates the work piece on its axis

A lathe is a machine tool that rotates a workpiece about an axis of rotation to perform various operations such as cutting, sanding, knurling, drilling, deformation, facing, and turning, with tools that are applied to the workpiece to create an object with symmetry about that axis.

<span class="mw-page-title-main">Forging</span> Metalworking process

Forging is a manufacturing process involving the shaping of metal using localized compressive forces. The blows are delivered with a hammer or a die. Forging is often classified according to the temperature at which it is performed: cold forging, warm forging, or hot forging. For the latter two, the metal is heated, usually in a forge. Forged parts can range in weight from less than a kilogram to hundreds of metric tons. Forging has been done by smiths for millennia; the traditional products were kitchenware, hardware, hand tools, edged weapons, cymbals, and jewellery.

<span class="mw-page-title-main">Machine tool</span> Machine for handling or machining metal or other rigid materials

A machine tool is a machine for handling or machining metal or other rigid materials, usually by cutting, boring, grinding, shearing, or other forms of deformations. Machine tools employ some sort of tool that does the cutting or shaping. All machine tools have some means of constraining the workpiece and provide a guided movement of the parts of the machine. Thus, the relative movement between the workpiece and the cutting tool is controlled or constrained by the machine to at least some extent, rather than being entirely "offhand" or "freehand". It is a power-driven metal cutting machine which assists in managing the needed relative motion between cutting tool and the job that changes the size and shape of the job material.

<span class="mw-page-title-main">Metalworking</span> Process of making items from metal

Metalworking is the process of shaping and reshaping metals to create useful objects, parts, assemblies, and large scale structures. As a term it covers a wide and diverse range of processes, skills, and tools for producing objects on every scale: from huge ships, buildings, and bridges down to precise engine parts and delicate jewelry.

<span class="mw-page-title-main">Machining</span> Material-removal process; manufacturing process

Machining is a manufacturing process whereby a desired shape or part is achieved by the controlled removal of material from a larger piece of raw material by cutting; it is most often performed with metal material. These processes are collectively called subtractive manufacturing, which utilizes machine tools, in contrast to additive manufacturing, which uses controlled addition of material.

<span class="mw-page-title-main">Try square</span> Woodworking tool used for marking and checking 90° angles

A try square or try-square is a woodworking tool used for marking and checking 90° angles on pieces of wood. Though woodworkers use many different types of square, the try square is considered one of the essential tools for woodworking.

Broaching is a machining process that uses a toothed tool, called a broach, to remove material. There are two main types of broaching: linear and rotary. In linear broaching, which is the more common process, the broach is run linearly against a surface of the workpiece to produce the cut. Linear broaches are used in a broaching machine, which is also sometimes shortened to broach. In rotary broaching, the broach is rotated and pressed into the workpiece to cut an axisymmetric shape. A rotary broach is used in a lathe or screw machine. In both processes the cut is performed in one pass of the broach, which makes it very efficient.

<span class="mw-page-title-main">Grinding machine</span> Machine tool used for grinding

A grinding machine, often shortened to grinder, is a power tool used for grinding. It is a type of machining using an abrasive wheel as the cutting tool. Each grain of abrasive on the wheel's surface cuts a small chip from the workpiece via shear deformation.

<span class="mw-page-title-main">Chuck (engineering)</span> Clamp used to hold an object with radial symmetry, especially a cylinder

A chuck is a specialized type of clamp used to hold an object with radial symmetry, especially a cylinder. In a drill, a mill and a transmission, a chuck holds the rotating tool; in a lathe, it holds the rotating workpiece.

<span class="mw-page-title-main">Hand scraper</span>

A hand scraper is a single-edged tool used to scrape metal or other materials from a surface. This may be required where a surface needs to be trued, corrected for fit to a mating part, needs to retain oil, or to give a decorative finish.

<span class="mw-page-title-main">Surface plate</span> Flat surface used as a reference plane

A surface plate is a solid, flat plate used as the main horizontal reference plane for precision inspection, marking out (layout), and tooling setup. The surface plate is often used as the baseline for all measurements to a workpiece, therefore one primary surface is finished extremely flat with tolerances below 11.5 μm or 0.0115 mm per 2960 mm for a grade 0 plate. Surface plates are a common tool in the manufacturing industry and are often fitted with mounting points so that it can be an integrated structural element of a machine such as a coordinate-measuring machine, precision optical assembly, or other high precision scientific & industrial machine. Plates are typically square or rectangular, although they may be cut to any shape.

<span class="mw-page-title-main">Lapping</span> Process of removing material from two workpieces

Lapping is a machining process in which two surfaces are rubbed together with an abrasive between them, by hand movement or using a machine.

<span class="mw-page-title-main">Wiggler (tool)</span> Tool used on a machine to accurately align the head with the work prior to machining

A wiggler, also known as a wobbler, edge-finder, center-finder or laser-centering-device, is a tool used with a machine like a mill, to accurately align the machine head with the work prior to machining.

<span class="mw-page-title-main">Investment casting</span> Industrial process based on lost-wax casting

Investment casting is an industrial process based on lost-wax casting, one of the oldest known metal-forming techniques. The term "lost-wax casting" can also refer to modern investment casting processes.

<span class="mw-page-title-main">Grinding (abrasive cutting)</span> Machining process using a grinding wheel

Grinding is a type of abrasive machining process which uses a grinding wheel as cutting tool.

<span class="mw-page-title-main">Honing (metalworking)</span> Production of a precise surface on a metal workpiece

Honing is an abrasive machining process that produces a precision surface on a metal workpiece by scrubbing an abrasive grinding stone or grinding wheel against it along a controlled path. Honing is primarily used to improve the geometric form of a surface, but can also improve the surface finish.

<span class="mw-page-title-main">Burnishing (metal)</span> Deformation of a metal surface due to friction

Burnishing is the plastic deformation of a surface due to sliding contact with another object. It smooths the surface and makes it shinier. Burnishing may occur on any sliding surface if the contact stress locally exceeds the yield strength of the material. The phenomenon can occur both unintentionally as a failure mode, and intentionally as part of a metalworking or manufacturing process. It is a squeezing operation under cold working.

<span class="mw-page-title-main">Precision glass moulding</span> Production of optical glass without grinding and polishing

Precision glass moulding is a replicative process that allows the production of high precision optical components from glass without grinding and polishing. The process is also known as ultra-precision glass pressing. It is used to manufacture precision glass lenses for consumer products such as digital cameras, and high-end products like medical systems. The main advantage over mechanical lens production is that complex lens geometries such as aspheres can be produced cost-efficiently.

Surface grinding is done on flat surfaces to produce a smooth finish.

In manufacturing and mechanical engineering, flatness is an important geometric condition for workpieces and tools. Flatness is the condition of a surface or derived median plane having all elements in one plane.

References

  1. W A J Chapman (1964), Workshop Technology, Part 1, Edward Arnold