On mild steel, an oxy-fuel cutting tip is graded from size 00 up through size 4 and beyond, with each step roughly doubling the oxygen flow needed to maintain a clean kerf; a 0/00 tip covers 1/8 to 3/8 in. stock, sizes 1–3 cover 1/2 in. to 3 in., and tips above size 4 reach plate up to 12 in. thick [S5][S1]. The selection is not a single decision but a four-step gate, and missing any one of the steps costs cut quality or operator safety.
This guide is written for a process engineer or shop foreman specifying a hand torch, a oxy-fuel cutter on a track, or the tip stock a fabrication shop keeps on the shelf. The numerical bands below come from manufacturer tip charts and operator references published through May 2026 [S1][S2][S3][S5].
The 4-Step Selection Gate: Seat, Thickness, Application, Fuel
Step 1 is seat type, and it is non-negotiable: the cutting tip must match the torch model because seat geometry varies by brand and a mismatch risks flammable gas leakage or a blown seat [S1]. Step 2 is plate thickness, which dictates the size of the central cutting-oxygen orifice and the preheat orifices; oxy-fuel equipment as a class is rated for mild steel from 3 mm (1/8 in.) up to 300 mm (12 in.) [S1]. Step 3 is application, splitting into hand cutting, machine/track cutting, gouging, and heating, with machine tips designed for higher cutting-oxygen pressures to give cleaner, more accurate kerfs [S1]. Step 4 is fuel gas, because each gas has its own flame chemistry, preheat behavior, and tip-drill pattern [S1].
The seat-type rule is the one most often skipped in the field. Two tips that both read "size 3" on the box will not interchange between a Harris-style torch and a Koike or ESAB machine torch without an adapter, and forcing a mismatch is the most common path to a leaking preheat seal.
Plate Thickness Bands and the Tip-Size Table
The clearest published bands map as follows: size 00 covers 1/8 in. to 1/4 in. mild steel, size 0 covers 1/4 in. to 3/8 in., sizes 1–2 cover 1/2 in. to 1 in., size 3 covers roughly 1 in. to 3 in., and size 4 and larger handles thick plate up to 12 in. [S5]. The preheat orifice is sized together with the cutting-oxygen orifice, which is why the same nominal "size" cannot be reused across fuel gases without re-checking the chart [S1].
An operator reference from 2009 on a Victor-style HC1200C outfit gives a concrete mid-band data point: 10–15 psi acetylene with a 7 or 8 size tip, 45–55 psi cutting oxygen, and a 3/8 in. hose is a common mid-thickness setup [S4]. That 45–55 psi cutting-oxygen window is the band to anchor pressure-guage settings when the manufacturer's tip chart is missing, and the 3/8 in. hose is the minimum ID for the larger tip sizes, because smaller hoses starvel the cutting oxygen and the kerf drifts.
Pretreat Pressure and Preheat Numbers by Fuel Gas
Mild steel must reach roughly 1,600–1,800 °F before the cutting-oxygen stream can sustain oxidation, and the preheat flame is what gets it there [S2]. Acetylene delivers a flame temperature of 5,600–5,800 °F, the hottest of the common fuel gases, with short preheat times, which is why it is the default for general work despite being the most expensive [S1]. Propylene and propane-blend fuels burn cooler and need longer preheat, but they cut and gouge more efficiently per dollar on large heating jobs [S1].
Rust and mill scale are not a reason to abandon the cut: the preheat flame burns off the oxide layer, exposing clean metal for the ignition reaction, which is why rusty plate is still inside the oxy-fuel envelope with the correct preheat time [S2]. For thin plate under about 1/8 in., smaller tips are mandatory, because too much heat and oxygen will melt rather than cut the steel, leaving warping and a heavy slag bead [S2].
Hand Torch vs. Machine Torch: Same Tips, Different Pressures
The same tip-size logic applies to both, but a machine torch on a straight-line cutting machine runs higher cutting-oxygen pressure to push a faster travel speed and a narrower kerf. Manufacturer machine-tip charts typically quote cutting oxygen at 80–110 psi for the mid-thickness sizes, against the 40–55 psi typical of a hand cut [S3][S4]. That pressure gap is the difference between a hand torch and a track torch even when the tip-size number on the box is identical.
Nozzle bore and orifice geometry are the second variable: larger nozzles with larger orifices allow higher gas flow and therefore higher cutting capacity, but they also demand a longer preheat time to stabilize the flame before the cutting oxygen is opened [S3]. For a structural shop cutting 1/2 in. to 1 in. plate on a track, size 1–2 machine tips with 70–90 psi cutting oxygen are the typical workhorse setup [S3].
Common Failure Modes and What They Tell You About Sizing
Too small a tip on thick plate shows up as a stalled cut, excessive slag, and a kerf that drifts; the cutting-oxygen orifice is simply not delivering enough volume to sustain oxidation through the full thickness [S5]. Too large a tip on thin sheet shows up as melted edges, a wide kerf, and warping because the heat input per inch of travel is far above what the plate can absorb [S2]. Either symptom is a sizing error, not a torch error, and the fix is to step to the next size in the correct direction.
Pre-heat problems are sometimes misread as tip problems: a long preheat followed by a sluggish start usually points to low acetylene or propylene pressure, not the wrong tip, while a sharp popping sound on ignition points to too high a preheat pressure for the tip [S1][S2]. A welding cutting tool on a properly sized tip should ignite in 2–5 seconds on acetylene for mid-thickness plate.
Standards, Sourcing, and Where to Verify a Chart
There is no single ISO or AWS standard number that defines a "size 3" tip across manufacturers; the tip-size convention is a de facto industry numbering used by Harris, Victor, Koike, and ESAB, with each maker publishing its own tip chart keyed to plate thickness, fuel gas, and cutting-oxygen pressure [S1][S2][S3]. That is why a shop standardizing on one torch brand and stock its tips is operationally simpler than mixing SKUs, and why the seat-type step in the 4-step method is the one that cannot be skipped [S1].
For a buyer, the actionable shortlist is: (a) lock the torch brand and seat type first, (b) pull the manufacturer's current tip chart for the chosen fuel gas, (c) verify the cutting-oxygen regulator can deliver the chart's pressure (typically 40–110 psi), and (d) keep the next size up and the next size down on the bench for the thickness you actually cut most. Sourcing through a riser cutting machine integrator or a general industrial supplier is the usual path for foundry work, and the same tip chart applies.
Trackable next signals to watch: the 2026 revision of major makers' tip charts (Harris, Victor, Koike, ESAB) for any shift in mid-band pressure numbers, and the gradual replacement of acetylene with propylene blends in EU shops driven by cylinder-handling regulations, which would push more demand for propylene-rated tip SKUs [S1][S2].
See also our earlier report, Pneumatic actuator types, mechanisms, and selection logic.