Which lubricant is best to prevent wear and increase cutting efficiency for tapping common steels?

Sulfur-based oil is particularly effective as a lubricant in the tapping process of common steels because it has unique properties that enhance performance in metalworking applications. This type of oil contains sulfur compounds that provide extreme pressure (EP) protection, which is critical during tapping as it minimizes tool wear and helps to prevent binding between the tap and the workpiece material.

When tapping steels, especially those that are alloyed or hardened, the pressures and friction involved can generate significant heat that can lead to both tool wear and workpiece damage. Sulfur-based oils are designed to withstand these conditions and can adhere to the surfaces, creating a protective barrier that reduces friction. Furthermore, the chemical reaction that occurs between sulfur and the metal surfaces can provide additional protection, resulting in longer tool life and improved cutting efficiency.

Other lubricants mentioned have their uses, but they do not possess the same level of EP protection or effectiveness for metals, particularly under the harsh conditions encountered during tapping operations. Water-based oils typically offer minimal lubrication and are more appropriate for operations where cooling is more critical than lubrication. Vegetable oils are generally suitable for lighter machining processes and may not provide the necessary properties for steel tapping, while mineral oils may lack the additives that enhance performance for specific tasks, such as tapping.