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Oxy-Cutting & Oxy-Acetylene Guide: Tips, Pressures, Flashback Arrestors & Safe Practice

Oxy-cutting (also called oxy-fuel cutting, gas cutting or oxy-acetylene cutting) is the portable, hand-held metal-cutting process that has powered Australian fabrication, demolition, mining and structural steel work for over a century. A preheating flame brings the steel to kindling temperature (around 870°C / 1,600°F — bright cherry red), then a high-pressure stream of oxygen oxidises the heated metal, blowing it out of the kerf as molten iron oxide. The Australian Steel Institute confirms the process cuts structural steel from 6mm to 300mm thick — the workhorse for severing structural plate that plasma can't reach and that mechanical saws can't approach. This guide goes deeper than the typical retail comparison content. It covers the AS 4603 flashback arrestor compliance that's often skipped, the tip-size-by-metal-thickness chart that determines whether your cut is clean or a hot mess, the forum-validated backfire vs flashback distinction that confuses beginners and apprentices, the oxy-acetylene vs oxy-LPG economic decision AU shops face, and the 9 common cutting problems with their fixes drawn from r/Welding, Practical Machinist and real-world AU workshop practice. It's the technical companion to our Welding Gas Regulator Guide (covering oxygen, acetylene and LPG regulators in depth), our Plasma Cutter Guide (the modern alternative for thinner work), and the broader welding cluster — see internal links throughout. Tip types — cutting, welding, heating, gouging — Quick Reference Quick reference for oxy-cutting & oxy-acetylene guide, drawn from the detailed section below. Tip type Function Example AIMS supply Cutting tip (Type 41) Ring of preheat orifices + central cutting oxygen orifice. Sized by metal thickness Bossweld Oxy/Acetylene Type 41 Cutting Tip Sizes 8, 12, 15 Welding tip Single central orifice — produces one focused flame for fusion welding thin steel Bossweld Oxygen/LPG Welding Tip Heating tip (rosebud / Type 551) Multiple-orifice flame ring for broad heat application — bending, straightening, paint stripping, shrinking Bossweld Oxygen/Acetylene Type 551 Heating Tip (8 × 12mm) Gouging tip Designed for surface metal removal (weld defect grooving, cast iron repair prep, casting cleanup) Bossweld Gouging/Cutting Attachment for A101 Torch + Gouging/Contact Cutting Nozzle HD Brazing tip Multi-orifice low-velocity flame for silver-braze work — typically interchangeable with welding tip Sourced via supplier network How oxy-fuel cutting actually works Oxy-fuel cutting is fundamentally different from plasma or mechanical cutting. It's a chemical oxidation process — the cutting oxygen burns the steel, it doesn't just melt it. Two stages happen: Stage 1 — Preheat. The torch's preheat flames (a ring of small flames around the central cutting orifice) heat the steel to its kindling temperature, around 870°C. At this temperature, iron will spontaneously combust in pure oxygen. The fuel gas (acetylene, LPG, propylene or natural gas) provides the heat for this preheat stage. Stage 2 — Cut. When the operator presses the cutting oxygen lever, a high-pressure oxygen jet (typically 200-400 kPa / 30-60 psi) blasts through the central orifice. The pure oxygen ignites the preheated steel, oxidising it to iron oxide (Fe3O4). The chemical reaction releases more heat than the preheat flames, propagating the cut downward through the plate. The molten oxide slag is blown out the back of the kerf by the oxygen jet pressure. The single most important consequence of this chemistry: oxy-fuel only cuts metals that oxidise easily — primarily mild steel and low-alloy carbon steels. Stainless steel forms a protective chromium oxide layer that resists further oxidation. Aluminium oxide melts at a higher temperature than aluminium itself. Cast iron's high carbon content makes the cut messy. See the metals section below for the full compatibility matrix. Oxy-Acetylene vs Oxy-LPG vs Oxy-Propylene — the AU decision The fuel gas choice is the biggest economic decision in an oxy-fuel setup. Three fuel gases are commonly used in Australia, each with distinct trade-offs. Oxy-Acetylene — the all-rounder Acetylene burns hotter than any other commercial fuel gas — about 3,150°C flame temperature with oxygen. It preheats fast (the #1 advantage on production cutting work), creates a tight reducing flame for welding, and is the only fuel gas that can both cut and gas-weld. The r/Welding forum reality: "Acetylene burns hotter. More effective at cutting thicker material and better burns." The trade-offs: acetylene is the most expensive fuel gas per cylinder in Australia, the cylinders are heavy (the gas is dissolved in acetone in a porous mass — a 7m³ G-size acetylene cylinder weighs ~75 kg), and the gas is unstable above 100 kPa (~14 psi) so the regulator's max delivery pressure is mechanically limited. Oxy-LPG (Oxy-Propane) — the AU value play LPG (mostly propane) is far cheaper per cylinder than acetylene in Australia. It's widely available, stable at higher pressures, and the cylinders are lighter and more compact. For workshops that only cut — never gas-weld, oxy-LPG is the AU economic winner. The counter-intuitive forum reality: LPG can cut thicker steel than acetylene when used with the right tip. r/Welding direct quote: "Propane can cut way thicker than acetylene. Get a 100lbs tank and the right tip and you can cut over 6 inches thick. Same thing with rosebud sizes." The reason: LPG flames have lower flame temperature (~2,800°C) but higher total heat output per unit volume of oxygen consumed — so more heat goes into the metal over time. The trade-offs: LPG cannot be used to gas-weld (Gasweld Australia: "Only Acetylene can also perform welding functionality") — the flame chemistry produces too much hydrogen and is too reducing for fusion welding. LPG preheats slower than acetylene — 30-60% longer preheat time on thick plate before the cut starts. LPG needs different cutting tips than acetylene — the orifice geometry is gas-specific. Oxy-Propylene — the production middle ground Propylene (sold as MAPP-equivalent or FG2/HPS-type fuel gases) burns hotter than LPG but cheaper than acetylene. Some AU shops use propylene for cutting-only operations where acetylene's preheat speed isn't required but LPG's slower preheat is unacceptable. Property Oxy-Acetylene Oxy-LPG/Propane Oxy-Propylene Flame temperature ~3,150°C ~2,800°C ~2,900°C Preheat speed Fastest Slowest (30-60% longer than acetylene) Medium Max practical cut thickness ~300mm 150mm+ (forum-reported 6"+ with right tip) ~200mm Can gas-weld? Yes No — cutting/heating only No Cylinder cost (AU) Highest Lowest Medium Cylinder safety Unstable >100 kPa — special handling Standard LPG handling — stable Standard handling Tip type required Acetylene-specific (Type 41) LPG-specific (separate tip) Propylene-specific Hose grade required Grade R (red, acetylene) Grade T (orange, all fuel gases including LPG) Grade T Best for Welding + cutting; thin-to-medium plate fast preheat Cutting-only workshops; thick plate; demolition Production cutting middle ground The AU workshop economic reality: if you only cut, switch to oxy-LPG and save substantially per cylinder. If you cut and gas-weld (brazing, silver-brazing, sheet metal fusion), stay with acetylene. Many AU shops run both — acetylene for welding/brazing setup, LPG on a separate cutting setup. Australian Standards — AS 4267, AS 4603, AS 4839, AS 5601 Oxy-fuel safety in Australia is governed by a stack of standards. Compliance isn't optional — Safe Work Australia, state regulators and most insurance policies require the equipment to meet these standards. AS 4267-1995 — Pressure regulators for use with industrial compressed gas cylinders. Covers oxygen, acetylene, LPG and inert gas regulators. See our Welding Gas Regulator Guide for full coverage. AS 4603 — Flashback arrestors. Governs the design, testing and inspection of the safety devices that prevent flashback travelling upstream from the torch to the regulator and cylinder. Compliance is mandatory for AU workshops. AS 4839-2018 — Safe use of oxy-fuel equipment for cutting, heating, welding and brazing. The procedural standard that covers setup, operation and shutdown. AS/NZS 1335 — Specification for hoses for welding, cutting and allied processes. Defines hose grades (R, RM, T) and colour codes. AS 5601 — Gas installations. Relevant for fixed installations like manifold systems. AS 2473 — Valves for compressed gas cylinders. Type 10 (argon/inert), Type 10.5 (oxygen), Type 20 (acetylene, LH thread), Type 21 (LPG, LH thread). For practical operation, the two standards that matter daily are AS 4603 (flashback arrestor selection and inspection) and AS 4839 (setup and operation procedure). Both are addressed in detail below. The torch system — handle, mixer, cutting attachment, tips An oxy-fuel cutting torch is a modular system. Understanding the four components clarifies what each does and why each fails. Handle (also called the body or shank). The two control valves (oxygen and fuel) live here, along with the trigger or lever that controls the cutting oxygen jet. Quality handles have stainless steel valve stems, brass body construction, and threaded fittings to AS specs. Bossweld A101, Cigweld 88-3, Victor 100 series and equivalent handles are the AU professional standard. Mixer (also called the mixer head). Where the fuel gas and the preheat oxygen mix before entering the cutting tip. Some designs use injector mixing (the oxygen stream draws fuel in via venturi effect — safer in a low-pressure backfire), others use equal-pressure mixing (both gases enter at similar pressures — common on heavier industrial torches). Cutting attachment. The 90° head that converts the welding handle to a cutting torch. Adds the central cutting oxygen channel and the lever/trigger that fires it. Different attachments fit different handles — Bossweld A101 cutting attachment fits Bossweld A101 handles only. Tips (the consumable end). The replaceable nozzle that shapes the preheat ring of flames and the central oxygen jet. Tips are gas-specific — acetylene tips have different orifice geometry than LPG tips. Tips are size-specific — Type 41 size 8, size 12, size 15 etc. match different metal thicknesses. Tips are application-specific — cutting tips, welding tips and heating tips all look superficially similar but do different jobs. Tip types — cutting, welding, heating, gouging Tip type Function Example AIMS supply Cutting tip (Type 41) Ring of preheat orifices + central cutting oxygen orifice. Sized by metal thickness Bossweld Oxy/Acetylene Type 41 Cutting Tip Sizes 8, 12, 15 Welding tip Single central orifice — produces one focused flame for fusion welding thin steel Bossweld Oxygen/LPG Welding Tip Heating tip (rosebud / Type 551) Multiple-orifice flame ring for broad heat application — bending, straightening, paint stripping, shrinking Bossweld Oxygen/Acetylene Type 551 Heating Tip (8 × 12mm) Gouging tip Designed for surface metal removal (weld defect grooving, cast iron repair prep, casting cleanup) Bossweld Gouging/Cutting Attachment for A101 Torch + Gouging/Contact Cutting Nozzle HD Brazing tip Multi-orifice low-velocity flame for silver-braze work — typically interchangeable with welding tip Sourced via supplier network Don't confuse them. A cutting tip in a welding application gives no flame control; a welding tip in a cutting application has no oxygen channel and no cutting capability; a heating tip on thin sheet metal will warp the work in seconds. Tip size by metal thickness — the cut-quality table Tip size determines preheat-flame ring diameter, cutting-oxygen orifice size, and consequently the gas pressures and cutting speed for a given metal thickness. Use the wrong size and your cut is either ragged (too small) or grossly oversized with massive kerf width (too large). The Bossweld Type 41 (oxy-acetylene) tip series uses metric numbering — size 8 (smallest standard), 12, 15, 20, etc. Each manufacturer publishes a tip chart. Forum reality from r/metalworking: "Victor makes a tip chart with tip size, steel thickness, and gas pressures all listed." Always reference the manufacturer chart for the specific tip series you're using. Metal thickness Type 41 size Oxygen pressure Acetylene pressure Cutting speed (mm/min) Kerf width 3-6mm (1/8 - 1/4") Size 8 200 kPa (30 psi) 30 kPa (4 psi) 500-650 1.5mm 6-12mm (1/4 - 1/2") Size 12 275 kPa (40 psi) 40 kPa (6 psi) 400-550 2.0mm 12-25mm (1/2 - 1") Size 15 350 kPa (50 psi) 50 kPa (7 psi) 250-400 2.5mm 25-50mm (1 - 2") Size 20 400 kPa (60 psi) 60 kPa (9 psi) 200-300 3.0mm 50-100mm (2 - 4") Size 24 450 kPa (65 psi) 70 kPa (10 psi) 150-200 3.5mm 100-200mm (4 - 8") Size 30+ 500 kPa (75 psi) 80 kPa (12 psi) 100-150 5.0mm+ 200-300mm (8 - 12") Heavy tip (special) 550 kPa (80 psi) 100 kPa (max acetylene) 50-100 7.0mm+ Important: Never exceed 100 kPa (14 psi) on acetylene — acetylene decomposes spontaneously above this pressure. For thicker plate, the additional preheat capacity comes from larger preheat ring, not higher pressure. This is why thick cutting tips use multi-flame preheat rings. The forum-validated common mistake from r/Welding "Problems with oxyacetylene cutting on 3/4 plate": "Also check the tip size. It may be too small. You want a #2 or #3." Tip too small for the thickness = bad cut, no amount of preheat fixes it. The flame — neutral, oxidising, carburising Three flame chemistries cover all oxy-fuel applications. Setting the right flame is the most important skill in oxy-fuel work. Neutral flame — equal oxygen and fuel volumes. Two clear zones visible: a short bright inner cone and a longer pale outer envelope. The hottest flame chemistry and the workshop default. Used for cutting mild steel, fusion welding, brazing. Oxidising flame — excess oxygen. Inner cone shorter and sharper; whole flame hisses louder. Hotter than neutral but creates oxide scale on the work. Used for brazing brass (the oxide layer protects against zinc fuming), some cutting operations. Carburising / Reducing flame — excess fuel. Feathery acetylene plume extends past the inner cone. Cooler than neutral. Adds carbon to the steel — used for hardfacing, some specialty welds, flame straightening. Setting the flame Open fuel gas valve slightly, light at the tip with a striker (never a lighter or match — they put fingers in the gas stream). Adjust fuel until the flame just stops smoking — this is the "smoke point." Slowly add oxygen. The acetylene feather will retract back toward the cone. For neutral flame: add oxygen until the acetylene feather just disappears — the inner cone becomes sharp and well-defined. This is the workshop default. For oxidising flame: continue adding oxygen until the inner cone shortens by about 10%. Flame will hiss more loudly. For carburising flame: back off oxygen until a feathery acetylene plume extends 2-3× the length of the inner cone. The forum-validated common beginner mistake from r/Welding: "I get a nice feather with my acetylene and then I turn on my oxygen it starts to produce a nice blue flame. However..." Top answer: "Too much oxygen will always put out a torch. But make sure you have plenty of acetylene before..." — increasing oxygen past neutral can blow the flame out entirely. The cut procedure — step by step Mark the cut line with soapstone or a paint marker on the plate. See our Industrial Paint Marker Guide for marking tools. Set up the equipment per the AS 4839 procedure: cylinders secured upright, regulators fitted with flashback arrestors (see flashback section below), hoses connected (oxygen blue, fuel red), torch and cutting attachment fitted. Open cylinders — quarter turn first, then fully (acetylene to 1/2 turn maximum). Slow opening prevents regulator first-stage shock. Set regulator pressures from the tip size table above. Acetylene at the appropriate pressure for the tip size (never exceeding 100 kPa). Oxygen at the appropriate pressure. Open valves at the torch — fuel gas valve slightly, light with striker. Adjust flame to neutral per the flame setting procedure above. Preheat the start point — hold the torch with the inner cone tip 3-5mm above the plate edge. Wait until the steel glows bright cherry red (kindling temperature). Thick plate may need to preheat 20mm away from the actual cut edge to avoid initial slag splashback. Press the cutting oxygen lever smoothly. The cut should start immediately on properly preheated steel. Move the torch along the cut line at the speed that maintains a stream of sparks coming out the back of the plate. Maintain perpendicular angle — torch held vertical to the plate. Tilting causes wandering cuts and rough edges. Travel speed — slow enough that the cut continues through the full thickness, fast enough that the cut doesn't bell out. The r/Welding rule: faster travel reduces slag accumulation on the cut edge. Shutdown — release the cutting oxygen lever. Close fuel valve at the torch first, then oxygen (this is the safe sequence — closing fuel first quenches the flame instantly). Close cylinder valves, bleed the regulators (open torch valves briefly to drop gauges to zero), then close torch valves. Roll up hoses, store equipment properly. Flashback arrestors — the AS 4603 compliance system A flashback is the most dangerous failure mode in oxy-fuel work: the flame travels backward from the torch up the hose toward the cylinder. If the flame reaches the cylinder valve, the result can be a hose fire, regulator destruction or — in worst cases — a cylinder rupture or BLEVE. WorkSafe ACT direct: "A flashback arrestor is designed to contain a flashback and prevent it from penetrating into upstream equipment (ie hoses, regulators and gas cylinders)." How flashback arrestors work A flashback arrestor is a one-way safety device with two protection mechanisms (ESAB technical bulletin): a non-return valve that prevents reverse gas flow, and a flame arrestor element (sintered metal mesh) that quenches a flame travelling backward by dissipating its heat below the gas's ignition temperature. Some arrestors are resettable after a flashback event; others are single-use and must be replaced. The four-arrestor compliance position For full AS 4603 compliance, an oxy-fuel setup needs four flashback arrestors total: one at each end of each hose. That's: Oxygen regulator outlet (regulator-end oxygen arrestor) Oxygen hose at the torch (torch-end oxygen arrestor) Fuel regulator outlet (regulator-end fuel arrestor) Fuel hose at the torch (torch-end fuel arrestor) Some workshop setups skip the torch-end arrestors as a cost-saving measure — this is the "regulator-only" position. AS 4603 and Safe Work Australia guidance both recommend the full four-arrestor compliance for any sustained workshop use. Cigweld Comet Flashback Arrestor 4-Pack is sold as a complete-compliance bundle for this reason. Flashback arrestor expiry — the forgotten maintenance item Flashback arrestors have an expiry date. The sintered metal element degrades over time even without a flashback event — gas-borne contaminants, moisture and thermal cycling all reduce the element's flame-quenching capability. Most manufacturers specify a 5-year service life from date of manufacture, with annual inspection requirements in production environments. Worn arrestors should be replaced even if they appear visually intact. AIMS Bossweld flashback arrestor range: Bossweld Flashback Arrestor Oxygen Regulator End, Bossweld Flashback Arrestor Fuel Regulator End, Bossweld Flashback Arrestor Oxygen Torch End, plus matched twin packs. See the full range at /collections/welding-regulators. Backfire vs flashback — the critical distinction This is the single biggest knowledge gap that competitor retail content fails to address clearly. Backfire and flashback are different events with different severity. Backfire A backfire is a momentary popping sound from the torch — the flame goes out and may relight automatically. Usually harmless if it's a single isolated event. r/Welding direct quote: "The backfire (little pop when you shut off acetylene first) isn't dangerous. It is not the same thing as a flashback, which can be dangerous." Common causes of a single backfire: Tip touching the workpiece momentarily Tip overheating (most common cause — slag splash on hot work) Wrong oxygen-to-fuel pressure ratio Tip orifice partially blocked with debris Loose tip in the cutting attachment (the #1 cause per r/Welding multiple threads) Sustained backfire / flashback A sustained backfire — where the flame disappears into the torch and you hear a whistling or squealing sound as it burns inside the handle — is a flashback in progress. This is the danger condition. Immediate action: Close the oxygen valve at the torch immediately — this starves the flame. Close the fuel valve at the torch. Close both cylinder valves. Allow the torch to cool before any inspection — internal components may be at flame temperature. Inspect the flashback arrestor — if it operated, replace it (single-use designs) or reset and inspect (resettable designs). The workplace safety rule: NEVER put a sustained-backfire torch into water to cool it. The thermal shock can crack the brass body. Allow it to cool in open air. This rule comes from r/Welding workplace training and AS 4839 procedure. Diagnosing single popping events Single backfires during cutting are not dangerous but indicate something is wrong. r/Welding forum diagnostic order: Check tip seating first. The #1 cause per multiple threads. Tighten the tip in the cutting attachment. Check tip orifice cleanliness. Use a tip cleaner (a set of fine drill-like wires) to clear preheat orifices and central oxygen orifice. Check pressure ratio. Reset to the tip-size table pressures. Common error: oxygen pressure too high relative to fuel. Check air filter inside the tip. r/metalworking direct: "There is a hex screw inside the torch tip that is removable and contains an air filter." Some torch designs have this; clean or replace. Check for overheating. A tip that's been used continuously on thick plate may overheat — allow to cool before resuming. Common cutting problems — forum-validated diagnostic table Problem Cause Fix Torch popping continuously Tip not seated correctly (most common); dirty tip; wrong pressure ratio Tighten tip; clean orifices with tip cleaner; reset pressures from tip-size table Flame blows out when oxygen added Too much oxygen pressure relative to fuel; fuel valve restricting flow r/Welding: "Too much oxygen will always put out a torch. Make sure you have plenty of acetylene before..." Open fuel further then add oxygen Slag splashing back at operator Travel too slow; tip too low; not enough cutting oxygen Increase travel speed; raise torch slightly; check oxygen pressure Cut wandering / not following line Torch not perpendicular to plate; inconsistent travel speed Hold torch vertical; use a straight-edge guide for long cuts; practice consistent motion Slag/bubbles on cut edge Travel too slow; tip too small for thickness; insufficient cutting oxygen r/Welding: "Move faster but there's always going to be slag when cutting." Step up tip size if persistent Won't start cutting on thick plate Insufficient preheat; tip too small; plate surface contamination Preheat longer; check tip size against thickness; remove paint/rust at start point Ragged cut edge Tip too small for thickness; oxygen pressure too low; travel too fast Increase tip size one step; raise oxygen pressure; slow travel Excessive kerf width Tip too large for thickness; oxygen pressure too high Reduce tip size; reset oxygen to chart value Smoke/orange flame on lighting Fuel not adjusted to smoke point before adding oxygen Light fuel only, adjust until flame just stops smoking, then add oxygen gradually Cutting different metals — what works and what doesn't Metal Oxy-cut? Notes Mild steel (carbon steel) Yes — workshop default The process is designed for this. Clean, fast cuts from 3mm to 300mm thick Low alloy steel Yes Standard procedure. Higher alloy content needs more preheat Stainless steel (304, 316, 410) No (in practice) Chromium oxide layer resists oxidation. Use plasma cutting, water jet or mechanical methods. See Plasma Cutter Guide Aluminium No Aluminium oxide melts higher than aluminium itself — no cutting reaction possible Cast iron (grey) Limited — possible with technique High carbon content forms graphite that doesn't oxidise cleanly. Cut quality is poor; rough but functional Cast iron (ductile) Possible Better than grey cast iron but still messy compared to mild steel Copper / bronze / brass No Doesn't oxidise. Use mechanical methods or plasma Titanium No (and dangerous) Titanium burns aggressively in oxygen — never attempt Galvanised steel Yes — but with hazard warning Zinc coating produces zinc oxide fume — respiratory hazard. Use forced ventilation or P3 respirator. See Respirator Guide Painted/coated steel Yes — clean the cut line first Paint produces toxic fumes when burned. Remove paint at the cut line with a wire brush or sander before cutting Australian Steel Institute confirms the practical range: "Oxyfuel gas cutting is the most common process used for severing structural steel. Structural steel thicknesses from 6 to 300mm can be cut using this process." Hoses, fittings and the AS/NZS 1335 colour code Oxy-fuel hoses are governed by AS/NZS 1335. Three hose grades exist: Grade R — for acetylene only. Red hose. NBR/EPDM rubber compounds compatible with acetylene only. Grade RM — also acetylene-rated, more flexible compound. Grade T — universal fuel gas hose. Orange/red. Compatible with acetylene, LPG, propane, propylene, natural gas. The Practical Machinist recommendation: "You need to use a T grade fuel hose, if you want to run both gases." The colour convention in Australia and the UK: Blue — oxygen hose Red / orange — fuel gas hose (acetylene, LPG, propane) Twin hose assemblies (oxygen + fuel pre-fitted side by side) simplify routing. AIMS Bossweld twin hose range: Bossweld Oxygen/LPG Twin Hose Assembly, Bossweld Twin Oxygen & Acetylene Hose 5mm, Bossweld Twin Oxygen & LPG Hose 5mm. For long-run installations, Retracta oxy-fuel hose reels are available — Retracta R3 1/4" × 15m Oxy & Acetylene Hose Reel (OA215B-04, black or natural). Hose fittings: Oxygen connections are right-hand thread. Fuel gas connections are left-hand thread — this is the safety convention that prevents cross-fitting an oxygen hose to a fuel cylinder or vice versa. The fitting nut also has a notch on fuel-gas fittings as a visual indicator. Cylinder handling and safety Store cylinders upright with valve protection caps fitted when not in use. Secure to a wall, post or trolley with a chain. Acetylene cylinders must be stored upright — liquid acetone (the carrier) can be drawn into the regulator if the cylinder is laid down. Keep oxygen and fuel cylinders separated when stored — minimum 3 metres apart, or with a fire barrier between them. "Crack" the valve briefly before fitting a regulator — open the valve momentarily to blow out any dust or moisture from the outlet. Stand to the side, not in line with the valve outlet. Open valves slowly — particularly oxygen. Snapping a valve open hits the regulator first stage with full cylinder pressure. Acetylene cylinder valve — open only 1/2 turn maximum. Provides full flow and allows immediate shutoff in emergency. Empty cylinders — close valve, mark "MT" (empty) clearly, return for refill. Never leave an empty cylinder unsecured. Oxygen and oil don't mix. Oxygen regulators, fittings and hoses must be oil-free — never lubricate. Petroleum products + high-pressure oxygen = spontaneous combustion. See our Welding Gas Regulator Guide for oxygen-specific regulator rules. Acetylene above 100 kPa is unstable — never increase regulator pressure above the AS 4267 mechanical limit. Asphyxiation hazard — argon, CO2 and other inert gases can accumulate in enclosed spaces. Always work with ventilation. Tip cleaning — the daily maintenance routine A clean tip is the difference between a clean cut and a popping mess. Tip cleaning is the daily maintenance routine. r/pipefitter direct quote: "Always keep a good torch tip, tip facer and tip cleaner in your carharts." Two distinct maintenance operations: Tip cleaning — using a set of fine drill-like wires (tip cleaners) to clear debris from each preheat orifice and the central oxygen orifice. The wires are sized to match the orifices; use the largest wire that fits each orifice. Light circular motion only — don't ream or enlarge the orifices. Tip facing — using a tip facer (a small countersink-like tool) to clean the flat seating face of the tip where it meets the cutting attachment. A scarred or debris-coated seat face causes leaks and inconsistent flame — the #1 forum-flagged cause of unexplained popping. The forum-validated maintenance kit (r/pipefitter): tip cleaner set + tip facer + spare tips in the correct sizes for the work being done. All fit in a small tool wrap that lives with the cutting kit. Brand reality — AIMS vs the AU specialist market Oxy-fuel is one of the most competitive AU markets — many strong specialist players (Cigweld, BOC, Weldclass, Total Tools, Sydney Tools, RivetLab, Huck Aerobolt, Total Steel) compete on price, service depth and brand reputation. AIMS plays the trade-tier consumable depth with Bossweld single-vendor coverage. Brand Tier Origin Forum / market reputation AIMS supply Bossweld AU industrial — AIMS dominant AU welding consumables specialist Full oxy-fuel ecosystem at workshop price-point. Cutting tips (Type 41), heating tips (Type 551), welding tips, twin hoses, flashback arrestors, gouging attachments. AS-compliant. ✓ 25+ SKUs — complete oxy-fuel range plus 8 regulators (covered in regulator guide) Cigweld (Comet, BlueJet, CutSkill) AU professional standard AU — ESAB owned The AU welding professional benchmark. Comet for premium, BlueJet for mid, CutSkill for workshop. Used across AU industry for decades. Not stocked — specialty welding distributor channel BOC AU gas industry premium AU — Linde owned BOC supplies the gas; their equipment range matches. Premium pricing reflects gas-contract integration. Not stocked — BOC direct channel Weldclass Platinum AU mid-premium AU brand Workshop-quality with longer warranties. 7-year warranty on Platinum kits. Not stocked — Weldclass direct/specialty UNIMIG AU welding equipment AU brand, China-made Mid-tier value. Strong Total Tools / Sydney Tools presence. Not stocked — retail tool chain channel Tesuco AU specialty AU manufacturer AS 4267 specialty range. Strong in nitrogen high-pressure and oxy-fuel. Not stocked — specialty channel Hot Devil AU value AU brand Bunnings / Autobarn / Mitre 10 tier — consumer-trade crossover Not stocked — consumer channel Victor US professional USA — ESAB Practical Machinist gold standard. Anti-flashback valves built into newer torches. "New Victor torches have anti-flashback valves built in and are much safer than older, used sets." Not stocked — US specialty source Smith / Harris / Airco / Purox US professional USA Other US specialty brands referenced on Practical Machinist. Smith Little Torch popular for jewellery work. Not stocked — specialty source on request AIMS oxy-fuel range AIMS stocks the Bossweld oxy-fuel consumables ecosystem at the AU industrial trade tier — see the full range at /collections/welding-regulators for regulators and adjacent welding categories for the rest. Regulators (covered in dedicated guide): Bossweld Oxygen Regulator (single-stage twin gauge), Bossweld Oxygen Regulator (Side Entry), Bossweld Regulator Oxygen Side Entry Gaugeless, Bossweld Acetylene Regulator, Bossweld Acetylene Regulator (Side Entry), Bossweld Regulator Acetylene Side Entry Gaugeless, Bossweld LPG High Pressure Regulator, Bossweld Regulator LPG High Pressure Gaugeless. See our Welding Gas Regulator Guide for detailed selection. Flashback Arrestors (AS 4603 compliance): Bossweld Flashback Arrestor Oxygen Regulator End, Bossweld Flashback Arrestor Fuel Regulator End, Bossweld Flashback Arrestor Oxygen Torch End — for full four-arrestor compliance. Hoses: Bossweld Twin Oxygen & Acetylene Hose 5mm, Bossweld Twin Oxygen & LPG Hose 5mm, Bossweld Oxygen/LPG Twin Hose Assembly. Plus Retracta R3 1/4" × 15m Oxy & Acetylene Hose Reel (black and natural finishes) for hose-reel-fed workshop installations. Cutting Tips: Bossweld Oxy/Acetylene Type 41 Cutting Tip Size 8/12/15 (and other sizes via the supplier network), plus Bossweld Tip Nut to Suit Standard Cutting Attachment for replacement nuts. Heating Tip: Bossweld Oxygen/Acetylene Type 551 Heating Tip (8 × 12mm) — for bending, straightening and paint stripping work. Welding Tip: Bossweld Oxygen/LPG Welding Tip (note: LPG only welds in limited applications — see fuel gas discussion above). Gouging: Bossweld Gouging/Cutting Attachment for A101 Torch, Bossweld Gouging/Contact Cutting Nozzle HD for A101 Torch. Not stocked at AIMS: Cigweld Comet/BlueJet/CutSkill, BOC, Weldclass Platinum, UNIMIG, Tesuco, Bromic, Victor (US), Smith Little Torch (US jewellery specialty), and consumer-tier kits. AIMS plays the AU industrial trade tier with Bossweld single-vendor depth. Call (02) 9773 0122 or visit contact us for specialty brand sourcing. Adjacent welding guides: Welding Gas Regulator Guide (regulator detail), Plasma Cutter Guide (alternative cutting process for stainless, aluminium, and thin material), MIG Welding Guide, TIG Welding Guide, Stick Welding Guide, Welding Consumables Guide, Welding Helmet Guide, Respirator Guide (for galvanised cutting). Frequently Asked Questions What is oxy-cutting? Oxy-cutting is a chemical metal-cutting process. A preheating flame (acetylene, LPG or propylene mixed with oxygen) heats steel to its kindling temperature around 870°C. A high-pressure oxygen jet then oxidises the heated metal, burning it to iron oxide and blowing the molten slag out of the kerf. The Australian Steel Institute confirms structural steel from 6mm to 300mm thick can be cut by oxy-fuel. The process only works on metals that oxidise easily — primarily mild steel and low-alloy carbon steels. Stainless, aluminium and copper alloys cannot be oxy-cut. What's the difference between oxy-acetylene and oxy-LPG? Acetylene burns hotter (3,150°C vs 2,800°C for LPG) and preheats faster, making it the standard for production cutting and the only fuel gas that can also be used to gas-weld. LPG is significantly cheaper per cylinder in Australia and — counterintuitively — can cut thicker steel than acetylene when the right tip is used (forum-reported 6"+ with appropriate setup). LPG preheats slower (30-60% longer than acetylene) and cannot gas-weld. AU workshops that only cut benefit economically from oxy-LPG; workshops doing both cutting and gas-welding need acetylene. What is a flashback arrestor and do I need one? A flashback arrestor is a safety device that prevents a flashback (flame travelling backward up the hose from the torch toward the cylinder) from reaching the regulator or cylinder. It has two protection mechanisms: a non-return valve preventing reverse gas flow, and a flame arrestor element that quenches a flame by dissipating its heat below the gas's ignition temperature. AS 4603 governs design and inspection. Full compliance requires four arrestors — one at each end of each hose (oxygen regulator end, oxygen torch end, fuel regulator end, fuel torch end). Skipping arrestors is the most common AS 4603 non-compliance issue in AU workshops. Do flashback arrestors expire? Yes. The sintered metal flame-arrestor element degrades over time due to gas contaminants, moisture and thermal cycling. Most manufacturers specify a 5-year service life from date of manufacture, with annual inspection in production environments. After a flashback event, single-use arrestors must be replaced; resettable arrestors must be reset and inspected per the manufacturer's procedure. Replace any arrestor that fails its annual leak test or has reached its expiry date, even if visually intact. What's the difference between backfire and flashback? A backfire is a single popping sound where the flame momentarily extinguishes and may relight — usually harmless and caused by tip seating, dirty tip orifices, or wrong pressure ratio. A flashback is the dangerous condition where the flame travels backward into the torch handle (you'll hear whistling or squealing). r/Welding direct: "The backfire (little pop when you shut off acetylene first) isn't dangerous. It is not the same thing as a flashback, which can be dangerous." For sustained backfire/flashback: close oxygen at torch immediately, then fuel, then both cylinder valves. Allow torch to cool in open air — never quench in water. Why does my oxy torch keep popping? The forum-validated #1 cause is the tip not being properly seated in the cutting attachment. r/Welding direct: "Where is it popping? Whenever it happens to me at work, it's because the tip isn't seating properly." Other causes in order: dirty tip orifices (use a tip cleaner), wrong pressure ratio (reset to tip-size chart values), overheated tip (allow to cool), debris in the air filter inside the tip (some torch designs have a removable hex screw filter), and very rarely, regulator delivery problems. Check tip seating first before disassembling. What tip size do I need for X mm steel? For Bossweld Type 41 oxy-acetylene cutting tips: Size 8 covers 3-6mm, Size 12 covers 6-12mm, Size 15 covers 12-25mm, Size 20 covers 25-50mm, Size 24 covers 50-100mm. Each step up needs higher oxygen pressure and slower travel speed. Tip too small for the thickness produces ragged cuts and popping; tip too large creates excessive kerf width. r/Welding common mistake: "Also check the tip size. It may be too small. You want a #2 or #3" for 3/4" plate. Always reference your manufacturer's tip chart — different brands use different numbering. Can I oxy-cut stainless steel? Not practically. Stainless steel's chromium content forms a chromium oxide protective layer when heated that resists further oxidation — the essential oxy-cutting reaction can't propagate cleanly. Some specialty techniques (oxy-arc cutting, powder-injection cutting) exist but aren't workshop-practical. For stainless steel cutting, use plasma cutting (see our Plasma Cutter Guide), water jet, or mechanical methods (bandsaw, abrasive cutoff wheel). Can I oxy-cut aluminium? No. Aluminium oxide melts at a higher temperature than aluminium itself, so the oxide layer doesn't separate from the parent metal — there's no cutting reaction. Use plasma cutting, water jet or mechanical methods. Aluminium plate is commonly cut with carbide-tipped circular saws or bandsaws. What's the safe shutoff sequence? Close fuel valve at the torch first, then oxygen. This sequence quenches the flame instantly — closing oxygen first leaves a fuel-rich smoky flame. The Practical Machinist forum has long debates about this, with some advocating the reverse sequence to prevent backfire — but the AS 4839 and Safe Work Australia procedure standard is fuel-first. After torch shutoff: close both cylinder valves, then bleed regulators by opening torch valves briefly until gauges read zero, then close torch valves and roll up hoses. What pressure should I set my regulator at? Depends on the tip size and gas. For Bossweld Type 41 cutting tips: Size 8 at 200 kPa oxygen / 30 kPa acetylene; Size 12 at 275 kPa oxygen / 40 kPa acetylene; Size 15 at 350 kPa oxygen / 50 kPa acetylene. See the tip size table above. Critical limit: never exceed 100 kPa (14 psi) on acetylene — acetylene decomposes spontaneously above this pressure. AS 4267-compliant acetylene regulators are designed to prevent over-pressure delivery. For thicker plate that needs more preheat capacity, step up to a larger tip rather than increasing acetylene pressure. What hose do I need for oxy-fuel? AS/NZS 1335 specifies three hose grades: Grade R (acetylene only, red), Grade RM (acetylene, more flexible), and Grade T (universal fuel — acetylene, LPG, propane, propylene, natural gas). Practical Machinist direct: "You need to use a T grade fuel hose, if you want to run both gases." Colour convention in AU and UK: blue for oxygen, red/orange for fuel. Fittings are right-hand thread on oxygen and left-hand thread on fuel gas to prevent cross-fitting. Bossweld twin hose assemblies are pre-fitted oxygen + fuel pairs in standard 5mm bore. Do I need a licence to use oxy-acetylene in Australia? No specific licence is required to use oxy-fuel equipment, but workplace operators must be trained per Safe Work Australia and AS 4839 procedures. Some industries (mining, oil & gas, specific commercial premises) require certification or competency assessments. Insurance policies often specify training requirements. The cylinders themselves don't require a separate licence to own, but cylinder transport and storage are regulated under the dangerous goods code. How do I clean an oxy-cutting tip? Use a tip cleaner — a set of fine drill-like wires sized to match each orifice on the tip. Insert the correct-size wire into each preheat orifice and the central oxygen orifice with light circular motion. Use the largest wire that fits each orifice — don't try to enlarge orifices. Also "face" the tip — use a tip facer (a small countersink-like tool) to clean the flat seating face where the tip meets the cutting attachment. A scarred or debris-coated seat face is the #1 forum-flagged cause of unexplained popping. Keep tip cleaner, tip facer and spare tips with the cutting kit (r/pipefitter: "Always keep a good torch tip, tip facer and tip cleaner in your carharts"). Is oxy-cutting being replaced by plasma? For thin and medium material — yes, plasma has largely replaced oxy-cutting in AU sheet metal and structural shops up to about 25mm. For thick structural steel (50mm+), oxy-fuel remains the practical choice — plasma cutters that handle 50mm+ are expensive (3-phase, 200A+) and slower than oxy-fuel on heavy plate. For dirty cutting (rust, scale, paint over steel), oxy-fuel handles better than plasma. For stainless and aluminium, plasma replaces oxy completely. For demolition work, oxy-LPG remains the workshop choice — cheap, portable, no electricity required. See our Plasma Cutter Guide for the alternative. The AIMS Safety collection spans head, eye, hand, foot, respiratory and high-visibility protection to AS/NZS standards. For high pressure fittings, see our high pressure fittings range stocked across Australia. People Also Ask — Oxy-Acetylene Cutting & Welding Q: How does oxy-acetylene cutting work? Oxy-acetylene cutting uses a cutting torch with a central high-pressure oxygen jet surrounded by a ring of preheat flames. The preheat flames bring the steel surface to its ignition temperature (approximately 870 °C for mild steel), and the operator then opens the cutting oxygen lever — the high-velocity pure oxygen stream reacts chemically with the hot steel, causing it to oxidise (burn) rapidly and be expelled as slag from the kerf. This is a chemical cutting process, not melting — the base metal immediately adjacent to the cut remains relatively cool. Cast iron, stainless steel, and aluminium do not cut cleanly by this method because they form refractory oxides that resist the process. Q: What are the key safety requirements for oxy-acetylene equipment? Critical safety requirements include: fitting approved flashback arrestors on both the fuel and oxygen hoses at the torch and regulator ends; storing cylinders upright and secured to prevent falling; keeping oxygen cylinders well separated from fuel gas cylinders and away from oil or grease (oxygen in contact with hydrocarbons creates a fire risk); never using oxygen as a substitute for compressed air; regularly inspecting hoses for cuts, kinks, and perishing; and ensuring the working area has adequate ventilation to prevent gas accumulation. Regulators, hoses, and fittings must be rated for the specific gases in use. Q: What is the difference between a neutral, carburising, and oxidising flame? Flame character is set by the oxygen-to-fuel ratio. A neutral flame (equal volumes) has a well-defined inner cone and is used for most welding and heating of steel — it neither adds carbon to nor removes carbon from the weld pool. A carburising (reducing) flame has excess acetylene, giving a feathery secondary cone — used for welding high-carbon steel and hard-facing to prevent carbon burn-off. An oxidising flame has excess oxygen and a shorter, harsher cone — used for cutting and for welding brass and bronze. The wrong flame for the application can produce porosity, hard spots, or embrittlement in the weld. Q: Can oxy-acetylene equipment be used for heating and bending as well as welding and cutting? Yes — a rosebud or heating tip produces a broad, high-volume flame suitable for stress relieving, pre-heating before welding, bending bar stock, removing seized fasteners, and straightening distorted steel. The oxy-acetylene system is one of the most versatile heat sources in a workshop precisely because the same gas supply supports welding, cutting, brazing, and heating with only a change of tip. However, all the same safety precautions for cylinder handling, hose integrity, and flashback protection apply regardless of the operation.