| Machine thread type is used in a pre-tapped hole with or without a nut. The Oval Head or Raised Countersunk Head is functionally the same as any countersunk variety and offers a deeper and therefore stronger recess that is neater in appearance. Zinc plating froms a zinc carbonate film that greatly retards the corrosion rate in a normal atmosphere, which is similar to the aluminum oxide film that forms on aluminum that accounts for its low corrosion rate. |
