McGuire Glossary of Fastener Terminology

Z - 13 terms

ZERO (GAGING) - The process of positioning the magnified spread on an amplifier to a desired relative position on the scale. Zero is generally at midpoint of the full scale, but the spread may be positioned anywhere on the scale.

ZERO SIZE (GAGING) - The desired midpoint or nominal size of the feature being measured as it relates to the scale. On back-pressure systems, zero is usually the midpoint between the minimum and maximum allowable size. On the flow system, the zero size is generally the minimum size.

ZINC & GREEN, ELECTROPLATED - Used for "grounding screws" in electrical applications

ZINC - CLEAR - Zinc plating is applied through electrodeposition of zinc onto the substrate metal. For fasteners, this process is typically done through the barrel plating method. Zinc electroplating can be completed in acid chloride, alkaline or cyanide baths. A chromate conversion coating is then applied which provides the final layer of corrosion resistance to the plated part.

ZINC - PHOSTPHATE - Coating used for corrosion protection of finished fasteners. Better for paint ability and a uniform appearance.

ZINC ELECTROPLATING - Zinc electroplating is a common way to protect threaded fasteners from the effects of corrosion. Zinc electroplating can be completed in acid chloride, alkaline, or cyanide baths. Supplemental coatings are frequently applied to zinc electroplating. These coatings, such as zinc phosphate or chromate conversion, provide a protective passivation layer on the zinc which assists in reducing the corrosion rate.

ZINC ELECTROPLATING (ASTM B633) - Zinc Electroplating is also a protective coating against corrosion, blue gray in color, non-toxic, and can be used around food. Zinc plating performs better than cadmium in an industrial atmosphere, but not in a salt atmosphere. A clear Chromate dip is a protective film applied after electroplating, adding corrosion protection. A silicon dip can be added for aiding in assembly. Commercial grades of zinc electroplating are typically applied a minimum of 5 microns thick (.0002"). Zinc electroplating with a chromate dip must not show base metal corrosion products at 96 hours of salt spray testing per ASTM B117, but may show white corrosion at the edges. Thickness conversion factors: microns x .0394=mils, mils x 25.4=microns, mils x .0254=millimeters, mils x .001 = inches.

ZINC OR MANGANESE - Black in color. Added protection when oiled with a non-drying petroleum oil containing corrosion inhibitors. Good lubricity.

ZINC PHOSPHATE CONVERSION COATING - A zinc phosphate conversion coating is frequently added to zinc electroplated parts, such as bolt threads, to improve corrosion resistance. This type of chemical conversion coating provides a protective passivation layer on the zinc improving its corrosion resistance.

ZINC, ELECTROPLATED (CLEAR) - Blue to blue-white color. Most popular of all commercial plating because it is relatively economical and offers good corrosion resistance in environments not subject to excessive moisture. Commercial zinc plating has a standard minimum thickness of 0.00015 inches. Class 2A thread allowance is sizes No.8 and smaller may not accommodate this thickness. To avoid any reduction in the strength properties of these screws, a thinner coating may be acceptable.

ZINC- YELLOW - Resembles bright brass but has the iridescent streaks of color in it. It is a colored chromatic finish over zinc plate and offers good corrosion resistance, though it may contain hexavalent chromium which would render it non-RoHS compliant.

ZYGOLOGY - The science of fastening things together

ZYX TIP - A sharp tip point common on screws used for woodworking which provides a faster grip into the hardwood or softwood. Limits splits close to the edge of the wood surface. Designed to be safely extracted!