Oxyfuel cutting tips

Smith manual OM-262659J, August 2026, lists the two-piece propane SC40-2 row for 25 mm (1 in) metal. Cutting oxygen is 41 psig at the regulator and 40 psig at the torch. The 10 psig preheat oxygen entry applies to three-hose machine torches. Use the complete chart and approved setup for the exact torch and fuel. Smith Oxy-Fuel Regulators and Torches manual, OM-262659J, August 2026

The tip supplies preheat flame and cutting oxygen. Match tip series, torch, mixer, fuel, material thickness and gas delivery.

Preheat and cutting oxygen perform different jobs

The preheat flame mixes fuel gas with oxygen to bring the work to the temperature needed for cutting. A concentrated oxygen stream then supports the chemical reaction with the hot metal. Linde describes oxyfuel cutting as an oxygen–metal reaction, with the torch providing both the preheating flame and the cutting stream. It is therefore more than melting metal with a hot flame. Linde oxyfuel-cutting principles

Conventional oxyfuel cutting is principally used for mild and low-alloy steels. TWI distinguishes these from aluminum and stainless steel, for which the ordinary process is unsuitable. Special processes are outside that general claim. Do not extend a steel thickness chart to another alloy simply because the flame can heat it. TWI oxyfuel application guidance

A chart can specify cutting oxygen, preheat oxygen and fuel separately. Preheat demand depends on the selected tip and duty; it does not define the cutting-oxygen jet requirement. Likewise, increasing flame intensity is not a substitute for adequate cutting-oxygen delivery or the correct travel speed.

Construction follows the fuel and application

One-piece versus two-piece construction does not identify the fuel by itself. Harris identifies 6290 as a single-piece acetylene tip for relatively clean steel, 6290 N/NX as propane/natural-gas tips with general preheat, and 6290 NFF as a heavy-preheat propane/natural-gas family for more demanding surface conditions. These are named product distinctions, not a rule that every two-piece tip is for propane. Harris cutting-tip family descriptions

Harris also explicitly lists 6290-AC two-piece oxy-acetylene tips in its Tips on Cutting sheet. The inner and outer components, slots and orifices form a designed assembly. Keep the exact family designation when ordering or replacing components; matching the visible outside shape does not establish fuel compatibility. Harris Tips on Cutting, PN 9500593 Rev D, March 2014

Torch-family compatibility also includes the seating surfaces, retaining hardware and mixer arrangement. Harris' operating instructions require checking that both torch and cutting tip agree with the fuel gas. Identify the torch model and attachment before selecting the replacement tip, including whether the system uses an injector or equal-pressure arrangement. Harris torch operating instructions

Read charts with their pressure locations intact

Use a chart from the applicable current manual rather than a number copied from a similar-looking tip. Preserve material thickness, fuel, tip series, pressure units and location, and any distinction between hand and machine torches. Pressure and gas consumption are different quantities; psig is gauge pressure, while scfh is a standard volumetric flow rate.

A bounded example from Smith's OM-262659J, August 2026, page 40, is the SC40-2, a heavy-duty two-piece propane cutting tip, for 1 inch / 25 mm metal thickness:

Read both pressure locations and the three-hose preheat footnote against the exact torch and chart. Smith Oxy-Fuel Regulators and Torches manual, OM-262659J, August 2026

Hose length, bore, fittings and protective devices belong in the supply-system assessment. Check delivery under the manufacturer's specified flowing conditions rather than accepting a static gauge reading as proof that the tip receives enough gas. If a chart does not identify the measurement point or necessary operating conditions, resolve them with the manufacturer before using it as a setup specification.

Setup and shutdown remain manufacturer-specific

Keep the complete operating manual with the torch. Harris' instructions cover checking fuel compatibility, fitting the tip, checking connections for leaks and purging the gases separately before ignition. They also specify approved flashback arrestors on both gas hoses. Follow the equipment's prescribed sequence and device requirements rather than assembling a procedure from multiple brands. Harris torch operating instructions

For positive/equal-pressure oxy-acetylene mixers, Harris' published lighting/shutdown guidance calls for separate purging, regulator adjustment to the tip settings and checking settings with the cutting lever depressed. Its normal flame-extinguishing sequence closes the oxygen torch valve before the fuel torch valve. For an extended shutdown it separately addresses closing cylinder valves, purging lines, confirming zero gauge pressure and backing out regulator adjustment screws. This is a bounded description of that guidance, not a universal lighting recipe or an emergency-response sequence. Harris oxy-acetylene lighting and shutdown guidance

Inspection and cleaning preserve the designed passages

Before fitting a tip, inspect for damage and check that its cutting orifice and preheat passages are clear of dirt or slag. Smith's current manual requires this inspection and directs users away from equipment contaminated with oil or grease or otherwise damaged. Have defective equipment addressed by a qualified person rather than treating a new tip as a cure for every fault. Smith manual, OM-262659J, sections 6 and 9

Use cleaning tools intended for the actual construction. ESAB's OXWELD range distinguishes orifice burnishers, a brass-bristle spline brush for internal slots in two-piece nozzles, and a special set for high-speed nozzles. That distinction matters: a general cleaning wire is not evidence that every passage should be treated alike. ESAB OXWELD tip cleaners

For its specified two-piece tips, Harris recommends its E-9 cleaner and directs brushing along the preheat slots, not across them, to avoid damage. Cleaning should restore the intended passage, not enlarge or reshape it into an improvised size. Keep the manufacturer-defined inner/outer components together. Harris Tips on Cutting, Rev D, March 2014

Judge the process as well as the tip

SSAB identifies both nozzle distance and heat input, oxygen cutting pressure and speed as contributors to oxyfuel edge quality. It also explains that surface piercing can clog the nozzle with spatter and that piercing thickness capability depends on the equipment manufacturer. A tip's edge-cutting capacity therefore does not establish its piercing capacity. SSAB cutting-process guidance

For qualification, record the torch and tip family, fuel, material and thickness, chart revision, pressure locations and supply arrangement alongside the observed cut. Inspect kerf, edge roughness, dross and dimensional result. A larger tip, more preheat or higher pressure is not a universal remedy. See Cutting and shaping processes for the broader process context.