by: J. Jones, sourced from September 2009 issue of the Welding Journal
All oxyfuel cutting tips have several things in common. They all have a center-cutting oxygen hole, with openings around the center hole for the preheat flames. These openings may be holes or splines. Cutting tips are constructed of various metallic alloys by numerous manufacturers, but they are all designed to cut metal. So how does one know how to choose the best tip for the job? When choosing a cutting tip, one needs to know three basic things.
The first item is the type of torch being used in the process. The torch determines the design of the seating surface the cutting tip must have. The torch’s design also mandates the maximum oxygen flow. The oxygen flow determines the thickness of metal that can be cut. Note: Placing a cutting tip rated to cut ten inches in a torch designed to cut six inches is a common mistake.
The second item to consider is the fuel gas being used. Fuel gases have different burning rates, and the cutting tip must be designed to match the burning rate. The end of the cutting tip is recessed to match the type of fuel gas. Fuel gases also have different temperatures and BTU ratings. Tips designed as two-piece tips with splines to carry the preheat gases deliver many more preheat flames. Onepiece tips with preheat holes are available for many types of fuel gases. Keep in mind that a two-piece tip offers many more preheat flames than does a one-piece tip; however, when using acetylene, additional preheat flames are not necessary.
The third item to consider is the application. What is to be cut? What is the size of the cut? The material must be capable of being cut with the oxyfuel process. The cut size will determine the tip size needed. Manufacturers often provide literature that recommends the proper size tip to do the job with approximate flowing pressures and gas consumption (cubic feet per hour, ft3/h). Gouging, deseaming, scarfing, and rivet washing are applications where specially designed cutting tips assist the process. Choosing the proper tip is just one of the many decisions the operator makes when using the oxyfuel process. The equipment’s performance relies on the operator’s skill.