What type of oil is best used for cutting threads on steel pipe?

Using lard as a cutting oil for threading steel pipe is based on its properties that make it effective for reducing friction and heat during the cutting process. Lard is a natural animal fat that can provide a good lubricating effect, which is essential when working with metals. It forms a protective layer on the metal surface, helping to prolong the life of cutting tools and ensuring a smoother and cleaner cut.

Among the options presented, lard stands out because it can adhere well to the metal surfaces, reducing wear on the cutting taps and dies, which is crucial when threading steel pipe. Additionally, its natural consistency allows it to remain effective even under varying conditions that may be encountered during the cutting process.

In many cases, other oils like penetrating oil are designed primarily for lubrication and easing rusted or stuck parts rather than being specifically formulated for cutting. While they might provide some lubrication, they do not offer the same level of performance in terms of creating clean and precise threads. Similarly, pike and coal do not possess the ideal characteristics for cutting operations and could lead to poor results or even damage to the cutting tools.