Precision shafting provides the highest degree of accuracy, concentricity, straightness, and surface perfection attainable in commercial practice. Precision shafting can be used with motors, gear boxes, or as mill shafts.
Products are made of alloy steel, carbon steel, or stainless steel, and then case-hardened, through-hardened, or annealed. Alloy steels are ferrous alloys based on iron, carbon and high to low levels of alloying elements such as chromium, molybdenum, vanadium and nickel. Alloy steels have better hardenability properties than carbon steels. They also offer superior durability.
Stainless steels are corrosion-resistant, ferrous alloys that contain chromium or nickel additions. Precision shafting that is case-hardened is hard at the surface, but relatively soft at the core. Products that are through-hardened have the same hardness throughout the shaft. Unhardened or annealed precision shafting is also available.
Grade, dimensions, special features, coatings, and additional operations are important specifications to consider when selecting precision shafting.
There are two main grades: precision and ultra-precision. Precision grade shafts have a tightly-rated tolerance for roundness and shaft straightness per unit length. Ultra-precision shafts have a very tight tolerance for overall straightness and roundness.
Basic dimensions for precision shafts include shaft diameter or width, and maximum length. Shaft diameter or width is measured across the shaft; although some shafts are square, most are round. Most precision shafting is manufactured to standard lengths, but can be cut to specific lengths to meet a customer’s needs.
In terms of special features, precision shafts may be case-hardened or through-hardened but have annealed ends. Tubular shafts are case-hardened and hollow. Solid shafts are case-hardened but not hollow.
Some shafts are anodized to prevent corrosion and provide a harder surface finish. Others are coated with black oxide, ceramic, chrome, nickel, nitride, or Teflon® (DuPont Dow Elastomers). Precision shafting with chamfered ends, axial holes, male threads, and tapped holes is also available.
Additional operations can also be used to produce grooved shafts, keyed shafts, and precision shafts with stepped ends. Break-edge shafts are specially treated to remove burrs at the ends of the shaft. Typically, the break-edge process does not include end-chamfering, a process which bevels or angles one or both shaft ends.
BS 3021 - Shafting for marine purposes
ASTM A80 - Specification for cold finished carbon-steel bars and shafting