An oxy-fuel cutting torch sized to plate thickness and fuel gas is rated to sever mild steel from 1/8" (3 mm) up to 12" (300 mm) in commercial outfits, per a four-step selection method used by torch manufacturers [S2]. Cutting happens when a preheat flame brings the steel to roughly 1,600 to 1,800 °F, after which a high-purity oxygen jet oxidizes and ejects the molten material [S1].
This spec map walks through the seat type, metal thickness, application and fuel gas variables, then sets out the comparison logic buyers actually use on a shop floor. It complements broader handbook coverage of the oxy-fuel cutter family and the related cutting machine and riser-cutting machine categories used in foundry and steel work.
Preheat Flame and the Steel Ignition Window
Steel must reach its ignition temperature before the cutting oxygen stream can sustain the oxidation reaction, and mild steel requires preheat to roughly 1,600 to 1,800 °F before the cut becomes self-propagating [S1]. Below that band the oxygen jet sputters and the cut stalls; above it the kerf widens, slag volume rises, and the cut edge loses squareness.
Fuel-gas choice sets the upper bound of available flame temperature. Acetylene burns at about 5,600 to 5,800 °F in the primary flame, which is the hottest flame produced by any commercially used fuel gas and gives the shortest preheat time [S2]. Oxy-acetylene can therefore reach the 1,600 to 1,800 °F kindling point quickly on cold plate, which is why it remains the default for intermittent cutting in the 1/8" to 1" range, where a controlled kerf matters more than raw speed.
Tip Size, Plate Thickness, and Orifice Selection
Cutting tips must be matched to plate thickness because the center (cutting-oxygen) orifice and the surrounding preheat orifices are sized to deliver the correct oxygen mass flow at the correct pressure for a given thickness band [S2]. A tip that is too small starves the cut of oxygen on thick plate and produces a dragging, slug-bound kerf; a tip that is too large floods thin plate, burns through the back face, and warps the workpiece [S1].
Commercial chart coverage spans 1/8" (3 mm) up to 12" (300 mm) for general-purpose oxy-fuel outfits [S2]. In practice, a shop running 3/8" to 1/2" plate (the most common structural-fabrication duty) sits in the middle of the chart, where tip families offer 3" to 6" (75 to 150 mm) clean-cut capacity per pass with acetylene and similar capacity with propane on slightly slower travel speeds [S5]. Always cross-check the manufacturer's tip chart for the specific torch model, because the seat type and preheat-orifice geometry change between torch families even when the plate thickness is identical.
Fuel Gas Comparison: Acetylene vs Propylene vs Propane
Fuel-gas selection is the second-largest variable in oxy-fuel torch selection, after plate thickness. Acetylene gives the highest flame temperature (about 5,600 to 5,800 °F) and the fastest preheat, but it is the most expensive fuel per cubic foot and is not the most efficient gas for heating large areas [S2]. Propylene and propylene-based blends (often labelled generically as "propylene" in the trade) burn cooler than acetylene but hotter than pure propane; they are widely used for heating and bending because the larger, softer flame distributes heat over a wider zone, and they are typically cheaper per unit heat content than acetylene for long heating cycles [S2].
For buyers choosing between fuels, the comparison below summarizes the trade-offs drawn from the four-step selection method and field feedback:
Acetylene: flame temperature 5,600 to 5,800 °F, fastest preheat, widest tip availability, highest gas cost, shorter cylinder run-time per charge. Best for precision cutting 1/8" to 1", gouging, and any work where minimum preheat distortion matters [S2].
Propylene / LP-gas blends: lower flame temperature, longer preheat time, but cheaper per BTU and a softer, broader heating flame. Best for heating, bending, forge work, and cutting where the slightly slower travel speed is acceptable [S2][S5].
Propane (pure): the coolest of the three common fuels, the cheapest per cubic foot, and the slowest to preheat. Used where code or gas availability dictates, or where the operator is willing to trade travel speed for fuel cost; cuts are functional but rougher than acetylene at equal thickness [S5].
Spec implication: if a shop already runs a TIG welder supplier map for fabrication, the same acetylene infrastructure can support an oxy-fuel cutter for occasional cuts; if the duty is heavy heating and bending, plan on a dedicated propane or propylene rig rather than burning acetylene on heating tips.
Seat Type, Torch Body, and Duty Cycle
Seat type is determined by the torch brand and model, and it must match the cutting tip exactly; mismatched seats leak fuel gas, overheat the tip seat, and can flash back into the handle [S2]. The major North American seat families (Victor, Harris, Airco, Smith) are not interchangeable, so a buyer who standardizes on one torch brand locks in a single consumable supply chain for tips, nozzles, and heating heads [S2].
Torch body duty rating is the second body-level decision. Light-duty outfits are adequate for occasional shop and field cutting in the 1/8" to 1/2" range; medium-duty outfits (e.g. the Victor Medalist series or equivalent Harris model) handle up to about 5" plate in intermittent duty [S3]. Heavy-duty torches with longer barrels, larger valves, and heavier cutting attachments cover the 6" to 12" range that a foundry or shipyard might run, but they are physically larger and heavier, which trades against field-portability. For a buyer who also needs to mobilize a fabrication shop around a site, an excavator commissioning procedure or a diesel forklift selection guide addresses the broader equipment mix on a project site, while the torch spec remains a body-and-seat decision.
When Oxy-Fuel Loses to Plasma and Laser
Oxy-fuel is the wrong tool for aluminum, stainless, and other non-ferrous metals because the oxide layer does not melt below the base metal and the cut cannot sustain itself; plasma is the practical default for those materials [S3]. On thin steel plate under roughly 2" (50 mm), oxy-fuel remains cheaper than plasma or laser to buy and run, but plasma gives a narrower kerf, less dross, and cleaner edges on workpieces that go straight to a weld or a paint line without re-machining [S3].
For CNC production cutting of plate, a laser or high-definition plasma table is faster and more repeatable than an oxy-fuel gantry, and a fabricator running high volumes should think of oxy-fuel as the field-repair and back-up process rather than the primary cutting method. The same logic that pushes a buyer toward vision measuring machine selection for tight-tolerance part inspection pushes the cut-process choice away from oxy-fuel for production tolerance work.
Setup, Safety, and Consumable Life
Standard oxy-acetylene setup follows a fixed sequence: secure both cylinders upright, crack the cylinder valves to clear dust from the seat, attach the oxygen and fuel regulators with the correct inlet connection, connect color-coded hoses (green for oxygen, red for fuel), leak-test every joint with a soap solution or leak detector, and only then light the torch with the correct ignition order (open the fuel valve slightly, ignite, then add oxygen to a neutral flame) [S3]. Skipping the cylinder-cracking step is a common cause of regulator-seat damage and pressure-creep failure on the first job.
Specialty tips extend the useful range of a single torch body. Standard cutting tips cover general plate; gouging tips remove weld metal or surface defects; heating tips raise large areas to forging temperature. Some specialty tips reach 24" from the torch to access awkward cavities or to cut the base of an I-beam in place, and two-piece hybrid tips with a brass inner and copper outer extend service life under high-duty cutting [S2]. Buyers who cut heavy plate daily should plan a tip-replacement budget; tips that run hot, drag in the cut, or fail to maintain a clean preheat cone are at end of life and must be replaced before plate quality drifts.
Shortlist Logic for the Buyer
For a buyer deciding today, the shortest path through the spec is: (1) write down the maximum plate thickness the torch will see in the next 12 months, then add 50% headroom for tip wear and field improvisation; (2) pick the fuel gas based on whether the duty is mostly cutting (acetylene) or mostly heating and bending (propylene or propane); (3) lock the seat type to the torch brand whose tip supply chain you can actually keep stocked locally; (4) buy the body one duty class above the rated need, because mid-sized torches handle 80% of the work in any shop and the extra cost is recovered in tip life and operator comfort [S2][S3].
Trackable signals to revisit the spec in 6 to 12 months: the cost of acetylene per cylinder in your region, which sets the break-even point for switching routine heating work to propane; the availability of two-piece hybrid tips in your chosen seat type, which extends consumable life on heavy plate; and any change in plate mix (more stainless or aluminum work), which would push the cutting process off oxy-fuel entirely and onto plasma [S2][S3]. For a shop that also runs heavy fabrication or site erection, a parallel review of excavator service life triggers and the wider welding and cutting tool inventory keeps the oxy-fuel torch spec consistent with the rest of the equipment list.