Across all our precision metal polishing services, Metal Cutting has the tools, techniques, and expertise to meet the Ra surface finish requirements of your small metal parts. Whether you are looking for minimal deviation and the smoothest possible surface or a rough surface that provides maximum adhesion and light diffusion, our custom finishing can produce results superior to standard mass finishing.
The Parameters That Meet Your Needs
As the arithmetic roughness average, Ra is a calculation of the average length across all the tiny peaks and valleys along the mean line of a surface of small metal parts. It is by far the most common standard requested by customers for their surface finish goals, with requirements typically in microinch units of 8 Ra, 16 Ra, 32 Ra, or 63 Ra. In addition, customers sometimes ask for other surface finish parameters, such as Rz — the mean surface roughness calculated by averaging the five highest peaks and the five lowest valleys in the surface.
Although the different parameters for surface finish are calculated using different sets of data points, we have experience with the full range of terminology from Ra to Rz and the various units of measure in between. That means we are capable of working with you with all of the different parameters, as well as the standard Ra surface finish.
Our Ra Surface Finish Expertise
Here at Metal Cutting we specialize in producing the precise Ra surface finish that will meet your needs for metal parts with the correct level of wear and friction resistance, as well as resistance to cracks and other surface defects. We are highly knowledgeable in the technology used to determine the ideal surface finish for your application. That includes not only smooth low friction bearing surfaces and ultra high lifecycle, low friction surfaces, but also surfaces where a controlled degree of roughness is desired, such as plastic injection moldings, mandrels for over molding, or medical components where a shiny or slippery finish is detrimental to functionality.
Our services run the gamut from turning and grinding to burr-free cutting that makes use of a vast choice of abrasive cutting wheels to achieve a growing range of fine finishes, as well as lapping and mass finishing that can ultimately achieve 0.010 micrometer (less than 0.5 microinch). We can also achieve the rough finish your application may require, using techniques including turning, grinding, cutting, and sand blasting. Whether your need is for smoothness not to exceed 8 Ra or roughness with a minimum of 16 Ra, we can achieve not only a range of values for maximum and minimum surfaces, but also a restricted distribution of surface finish values.
We utilize a complete array of mechanical and optical testers for measuring Ra surface finish, with skills in surface finish interferometry as well as the use of sophisticated contact surface finish testers. Our advanced white light interferometer enables us to provide highly precise non-contact 3D metrology of surface profiles, while our compact contact surface testers allow us to take profile measurements anywhere on the shop floor.
Working with high volumes of small diameters far too small to be easily measured, we use Ra surface finish comparators to evaluate our end cut finishes side by side with the known results of typical grinding, honing, lapping, and polishing processes. These standard physical tools for basic visual comparison allow us to quickly and easily judge whether our results meets the standard for average surface finish in the typically requested customer requirements ranging from 63 Ra down to 8 Ra.
Fast Facts on Ra Surface Finish
- Controlled surface finishes as smooth as Ra 1 microinch (Ra 0.025 µm)
- Ability to tumble and polish to achieve 1 Ra or better
- Polishing of all metals, including hard metals and composites, in simple or complex shapes