Honing, Lapping, and Superfinishing Services
Achieve Perfectly Flat Surfaces with Honing, Lapping, and Superfinishing Services from Duval Precision Grinding
Duval provides grinding services for components that require ultimate precision. When surface finish tolerance requirements are extremely tight and simple grinding methods will not suffice, we have the ability to refine the surface finish of a component with advanced honing, lapping, and superfinishing services.
Honing, Lapping, and Superfinishing: What’s the Difference?
Superfinishing, lapping, and honing are three refinement methods used in metalworking; these methods smooth the outer surface of a metal and refine the geometry of precision components. Although the three processes are similar, each has a unique methodology, execution, and result.
Honing is a finishing process used to improve the geometry of a part, readjust the alignment of features such as holes or bores, and produce a finer surface finish. In the honing process, a small, bonded, abrasive stone or super-abrasive stick is rotated over the surface of a part over a controlled path. The honing stones are built with an abrasive grain held together with adhesive. Honing is a high-precision process and is used to improve certain form characteristics such as cylindricity, surface finish, or sphericity.
Lapping is a machining process used to achieve super-flat surfaces and incredibly tight tolerances on parts that require accuracy at the microscopic level. The lapping process involves passing a part between one or two large flat-lap plates or platens in a carrier fluid that contains an abrasive. The lapping process is more gentle than both superfinishing and honing and removes much less of the surface material. With lapping, Duval has the ability to produce a super-flat, polished surface. Lapping processes will generate one to three helium light bands (HLB) of surface flatness.
Superfinishing is used to refine the surface finish of a component to produce a very fine surface with an exceptionally low roughness average (RA). A fine-grit abrasive stone or tape is rotated over the component while the component is simultaneously spun in the opposite direction. This process removes the amorphous surface layer left by the last grinding process and leaves a recognizable crosshatch pattern. Superfinishing will increase the life of a part by decreasing wear and tear. It can also be performed to achieve a tighter tolerance and better sealing capabilities. Superfinishing will allow for a predictable, repeatable surface finish, as it removes any defects left over from the initial milling, turning, or grinding process. When parts are processed through superfinishing, their RA reading on a profilometer will be less than two.
Determining Surface Finish Depends on Accurate Measuring Methods
Duval ensures the accuracy of any surface-finishing process by measuring the flatness and roughness of a surface after finishing. There are a wide variety of methods that can be employed to measure surface flatness; Duval uses the most advanced measuring method available. This method employs a monochromatic light source and an optical flat.
When two monochromatic (i.e., single-wavelength) light sources interfere with each other, the light appears invisible and the reflecting surface appears black. For this measuring method, Duval uses a helium gas light source with a wavelength of about 0.6 microns or 0.000023″. A precision-ground and polished piece of optical-quality glass lapped flat on at least one side is placed on the piece to be measured. The light is then aimed at and reflected off of the part through the optical flat; this causes interference in the light bands.
If the distance between the optical flat and the piece being measured is an even multiple of the wavelength of the light source (e.g., one half), the band will appear black. This distance is referred to as a helium light band and should measure 0.3 microns, or 0.0000116″. With precision tolerances this tight, sophisticated seals between parts cannot be penetrated by solids unless the seal faces open.
The engineers at Duval Precision Grinding understand that the precision components they produce will be used in some of the most advanced equipment in the world. These high-powered machines need absolute, reliable, high-quality components in order to function to specification. One small defect can have potentially disastrous consequences.
When we say precision is our only product, we take this commitment seriously. When you need parts that are super-flat down to the microscopic level, we can provide precision results that will meet or exceed your expectations—every time. Don’t settle for inferior surface finishes; contact the experts at Duval today.
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