Cutting Methods in Steel Structure Construction
PCL Group application engineering, Jinan · Updated 20 October 2026
Steel structures are cut in two places: in the fabrication shop, where plates and sections are cut to drawing, and on site, where members are trimmed, coped or modified. Five methods do almost all of that work: oxy-fuel (flame), plasma, laser, sawing and drilling or punching. Each leaves a different edge, handles a different thickness range and costs a different amount per cut. This guide compares them for structural steelwork.
On this page
Quick pick by job
| Job | Usual method |
|---|---|
| Thick carbon steel plate, 50 mm and above | Oxy-fuel |
| Plate and sections up to medium thickness, lowest machine cost | Plasma |
| Parts with many bolt holes, slots and weld bevels that must fit first time | Fiber laser |
| Straight cut-to-length of beams and columns | Band saw |
| Bolt holes in thick flanges where the specification asks for drilling | Drill line |
| Stainless steel and aluminium | Plasma or laser (oxy-fuel cannot cut them) |
The five methods compared
| Oxy-fuel | Plasma | Fiber laser | Saw | Drill / punch | |
|---|---|---|---|---|---|
| Materials | Carbon and low-alloy steel only | Any conductive metal | Steel, stainless, aluminium | Any | Any |
| Thickness sweet spot | Thick to very thick | Thin to medium-thick | Thin to thick (to 40 mm on a 20 kW PCL beam laser) | Any section size within capacity | Limited by tooling |
| Edge and kerf | Wide kerf, slag, oxide layer | Narrower kerf, slight bevel, some dross | Narrowest kerf, clean square edge | Kerf of the blade, square end | Clean hole, exit burr |
| Heat-affected zone | Widest | Medium | Narrowest | None | None |
| Holes and slots | Large holes only | Holes above about 1.5× thickness | Small holes and slots, round | No | Round holes; slots need extra tooling |
| Weld bevels | Yes, with a bevel head | Yes, with a bevel torch | Yes, 5-axis heads to ±45° | Mitre only | No |
| Machine cost | Lowest | Low to medium | Highest | Low | Medium |
Oxy-fuel (flame) cutting
A preheat flame brings the steel to ignition temperature and a jet of pure oxygen burns through it. Because the cut is a chemical reaction with iron, it only works on carbon and low-alloy steel, and it is slow on thin plate. Its strength is thickness: oxy-fuel is still the standard way to cut very thick plate, and several torches can run at once on one gantry.
Use it for
- Base plates, gussets and heavy plate
- Rough cutting before machining
- Site work with portable equipment
Watch out for
- Wide heat-affected zone and distortion on long parts
- Oxide layer and slag to grind before welding or painting
- Poor results on small holes
Plasma cutting
An electric arc through a constricted gas jet melts the metal and blows it out of the kerf. Plasma cuts any conductive metal, is much faster than oxy-fuel on thin and medium plate, and costs far less than a high-power laser. CNC plasma beam cutters handle H-beams, channels, angles and pipe with copes, holes and bevels from one program.
Use it for
- Plates and sections up to medium thickness
- Copes, notches and larger holes
- Shops that need low machine cost
Watch out for
- Slight edge bevel and dross
- Small holes relative to thickness come out tapered
- Consumable wear affects quality
See how to cut an H-beam with a CNC plasma cutter.
Fiber laser cutting
A focused fiber laser beam melts a very narrow kerf, and an assist gas clears it. High-power fiber lasers have moved laser cutting from thin sheet into structural thicknesses: the PCL H-beam laser cuts flanges and webs up to 40 mm at 20 kW, with a 5-axis head for bevels. The edge is usually ready to weld or bolt without grinding, and bolt holes can meet the same tolerances as drilled holes.
Use it for
- Parts with many bolt holes and slots
- Weld-ready bevels and copes
- Marking part numbers and fit-up lines
Watch out for
- Highest machine cost
- Very thick plate is still faster with oxy-fuel
- Needs clean gas supply and trained operators
Related: laser-cut bolt holes tested against drilling and H-beam laser cutting machine.
Sawing, drilling and punching
Mechanical methods leave no heat-affected zone at all. Band saws are the traditional way to cut beams and columns to length, and drill lines put bolt holes into flanges and webs. Angle lines punch and shear angles for towers. Many fabricators still run a saw and drill line side by side; the newer approach is one CNC thermal machine that cuts length, copes, holes and bevels in a single pass. For that decision see laser, plasma and saw-drill lines compared.
On site
Site cutting is mostly oxy-fuel and portable plasma: trimming members, cutting openings and removing temporary attachments. Hot work on site needs a permit, fire watch and protection for nearby coatings. Wherever possible, cuts and holes should be made in the shop, where accuracy is higher and the work is safer.
Common questions
What is the most common cutting method in steel structure fabrication?
Sawing and drilling are still common for sections, plasma and oxy-fuel for plate. Fiber laser is growing fastest because it cuts holes, copes and bevels to fit-up accuracy in one pass.
Can oxy-fuel cut stainless steel?
No. Oxy-fuel cutting relies on iron burning in oxygen, so it only works on carbon and low-alloy steel. Use plasma or laser for stainless steel and aluminium.
Which cutting method has the smallest heat-affected zone?
Among thermal methods, fiber laser has the narrowest heat-affected zone, then plasma, then oxy-fuel. Sawing and drilling have none.