Originally written by Brooks Glover
Miyano’s fixed headstock type CNC automatic lathes are among the world’s strongest high-rigidity machines for heavy machining and include high rigidity spindles and a machine bed with platform-style construction. However, Miyano’s most impressive and key technology is the machine’s hand-scraped slideways.
At first, hand-scraping may seem outmoded compared to the amount of technology that goes into CNC machines, but the technique results in exceptional rigidity and damping abilities which allow surface contact over a wide area and enable powerful cutting required for hard turning operations. Hand-scraping involves a technician using a flat scraper on the part’s surface to remove incredibly small pieces of metal which can be as thin as two microns. This process is most commonly used to true a part’s surface, but machinists also use the technique to correct parts that do not mate correctly and to improve a surface’s ability to retain oil.
Hand-scraping also immensely improves the slideway’s ease-of-maintenance. To treat age-related wear on other slideways, the guide set must be replaced. In contrast, slideways that have been hand-scraped only require adjusting the gibs to recover high precision machining. With just this simple maintenance, precision levels can be kept for more than a decade.
To assure the surface is true as possible, technicians apply vermilion dye to a master level surface. The dye is then transferred to the slideway, by placing the master surface on top of the slideway. This applies the dye to the high points on the slideway’s surface and allows technicians to see what areas on the surface need to be scraped.
Hand-scraping is not the only advantage of Miyano’s slideways. Galling, a form of wear that occurs. When the material on one surface is pulled and removed by the contacting surface, is commonly caused by slideways’ repeated gliding motion. To prevent galling, other manufacturers lubricate slideways with a resin-based material. However, this method can cause other forms of wear over long periods of operation and can be subject to thermal expansion which affects the slideway’s movement.