The Lincoln Electric FlexCut 125 (K4811-1) is Lincoln Electric's most powerful conventional air plasma cutting system, rated at 125 amps at 100% duty cycle for all-day production plasma cutting in heavy fabrication, structural steel, and shipbuilding environments. As detailed on Lincoln Electric's FlexCut 125 product page, the K4811-1 ships as a power source only and is optimized for mechanized and CNC cutting applications where maximum throughput and minimum operating cost are the primary requirements. It is the plasma power source of choice for Lincoln Electric's Torchmate 4400 and 4800 series CNC tables configured for heavy-duty production use.
At 125 A and 100% duty cycle at every amperage setting, the FlexCut 125 is the only conventional air plasma system in its class designed for uninterrupted production cutting. Lincoln Electric's Torchmate documentation confirms the FlexCut 125 cuts 1/4 in. mild steel at over 200 ipm — faster than competing 105 A or 125 A plasma systems. Mechanized piercing to 1 in. (25 mm) mild steel and edge-start maximum capacity of 2 in. (50 mm) covers the heaviest structural and plate-cutting applications within conventional air plasma's range.
The FlexCut 125's patent-pending consumable design delivers up to six times longer electrode and nozzle life versus standard air plasma consumables. In production cutting environments with 100+ pierces per shift, this translates directly to fewer production stoppages for consumable changes and dramatically lower cost per linear foot of cut. The system also supports plasma marking using the same consumable set — making it the first conventional air plasma cutter to combine cutting, marking, and grid-cutting in a single power source without separate consumable change.
The FlexCut 125's full-color graphic display with one-knob process selection simplifies setup on busy production floors. The Parts-in-Place system detects correct consumable installation before arc initiation, preventing consumable damage from improper assembly — a feature that pays back quickly in shops where multiple operators share a single machine.
| SKU / Model | K4811-1 / FlexCut 125 (Power Source Only) |
| Process | Plasma Cutting, Plasma Marking, Grid-Cutting (PAC) |
| Input Voltage | 380 / 400 / 415 / 460 / 575 V, 3-Phase, 50/60 Hz |
| Rated Output | 125A / 175V / 100% (at all amperage settings) |
| Input Current @ Rated Output (3-Ph) | 40 / 40 / 40 / 33 / 28 A |
| Output Range | 20–125 A |
| Arc Start | Non-High-Frequency (blow-back/contact) — CNC-safe |
| Air Pressure Required | 90–120 PSI (6.21–8.27 Bar) |
| Air Flow Rate | 550 SCFH @ 90 PSI (260 SLPM @ 6.21 Bar) |
| Cut Capacity — Mild Steel (Mechanized Pierce) | 1 in. (25 mm) |
| Cut Capacity — Mild Steel (Max Edge Start) | 2 in. (50 mm) severance |
| Cut Speed (1/4 in. mild steel) | >200 ipm at 125 A |
| Display | Full-color graphic LCD with one-knob process selection |
| Consumable Safety | Parts-in-Place detection system |
| Plasma Marking | Yes — same consumable set, air or nitrogen |
| Net Weight | 118 lbs (53.5 kg) |
| Dimensions (H×W×D) | 20.72" × 12.25" × 25.53" (526 × 311 × 648 mm) |
| Warranty | 3 Years — Lincoln Electric factory |
| Condition | New — Lincoln Electric K-prefix (factory-new) |
- FlexCut 125 Plasma Power Source (K4811-1) — power source only
- Input power cord
- Operator's manual
- Note: Machine torch and consumables are sold separately. Compatible torch packages: LC125M machine torch (K4300-series) in 25 ft, 50 ft, and 75 ft leads. Consumable Starter Kit for Mechanized Cutting: K4302-2.
Complete your FlexCut 125 system with these Lincoln-compatible accessories:
- Plasma Machine Torches — LC125M machine torch leads (K4300-4: 25 ft, K4300-5: 50 ft, K4300-6: 75 ft) for CNC tables, pipe cutting systems, and structural cutting applications; straight and bevel torch head configurations for profile and bevel cutting automation.
- Plasma Consumables — Genuine LC125M electrodes, nozzles, swirl rings, and shields rated for 6× longer life than standard consumables; marking consumable kits for plasma marking with nitrogen or air; consumable starter kits (K4302-2) with full production quantity of all wear parts for initial machine commissioning.
- Air Treatment Systems — High-volume desiccant dryers and coalescing filter systems for the 550 SCFH @ 90 PSI air demand of the FlexCut 125; rotary screw compressor packages for dedicated plasma cutting stations; nitrogen supply regulators for plasma marking mode (nitrogen improves marking contrast and surface quality on stainless).
The FlexCut 125's 125 A output, 100% duty cycle, and 1 in. pierce capacity make it the production plasma cutter for demanding industrial applications:
- HVAC ductwork — large-format and structural HVAC fabrication. On CNC plasma tables, the FlexCut 125 cuts heavy-gauge spiral duct blanks, structural HVAC supports, and custom fittings in stainless and aluminized steel at production speeds that sustain fabrication shop throughput. The 200+ ipm cut speed on 14-gauge material allows a single CNC table to process full sheets in minutes, maximizing throughput in duct and fitting fabrication operations.
- Automotive and heavy-equipment bodywork. Structural frame sections, skid plates, and armor plate up to 3/4 in. cut cleanly with minimal dross at the FlexCut 125's production rates. The 1-in. pierce capacity handles thick chassis components and suspension brackets that exceed the capacity of smaller plasma systems. Plasma marking capability allows part numbers and bend lines to be marked directly on cut parts without a separate operation.
- Structural steel fabrication and structural ironwork. Heavy plate, wide-flange sections, and structural tube stock up to 1 in. cut clean and fast for steel fabricators, beam fabricators, and ironworkers. The 2-in. severance capacity handles weld joint access cuts, flame-cut replacement, and emergency structural cutting where thick plate must be removed quickly.
- Art, architectural fabrication, and custom metalwork. Decorative steel panels, architectural screens, and large-format custom metalwork cut on CNC tables at 125 A achieve edge finish quality that minimizes or eliminates secondary grinding on 1/4 in. and thicker mild steel plate. The plasma marking mode scribes layout lines, logos, and decorative elements directly on plate before or after cutting.
- Demolition, industrial MRO, and scrap processing. The 2-in. severance capacity and 100% duty cycle enable sustained demolition cutting of structural beams, heavy pipe, and thick plate in industrial demolition and MRO applications. Six-times consumable life reduces cost per cut in scrap processing where electrode wear is the primary variable operating expense.
The FlexCut 125 (K4811-1) achieves mechanized piercing up to 1 in. (25 mm) mild steel — the production-rated pierce start capacity for CNC plasma table operations. Maximum edge-start capacity (severance) is 2 in. (50 mm). At 125 A, cut speed on 1/4 in. mild steel exceeds 200 ipm, with 1/2 in. mild steel cutting at approximately 55–60 ipm. These figures are from Lincoln Electric's FlexCut 125 data sheet. Stainless and aluminum capacities are similar to mild steel at equivalent thicknesses.
The FlexCut 125 delivers 100% duty cycle at every amperage setting, from 20 A to 125 A. This is the defining production advantage of the FlexCut 125 over competing 125 A systems that typically derate to 60–80% at maximum output. For CNC plasma tables running sustained cutting programs, the 100% duty cycle eliminates thermal shutdown interruptions entirely at all production amperages.
Yes. The FlexCut 125 uses Lincoln Electric's non-high-frequency blow-back pilot arc system. The arc initiates without direct workpiece contact, enabling cutting on expanded metal, perforated plate, and surfaces with mill scale or paint without arc-start failures. The non-HF design is CNC-safe and does not interfere with motion controllers or torch height control systems. Parts-in-Place protection prevents arc initiation if consumables are improperly assembled, protecting both the torch and the workpiece from damage caused by misassembled consumables.
Yes. The FlexCut 125 (K4811-1) is optimized for CNC mechanized cutting and is the production plasma source for Lincoln Electric Torchmate 4800 and 5100 CNC tables configured for heavy-duty use. It provides divided arc signal output and full CNC interface for torch height control (THC) systems. Compatible machine torches (LC125M) mount directly to CNC carriage systems and are available in 25 ft, 50 ft, and 75 ft lead lengths. The system also supports non-table pipe cutting and structural beam cutting machinery.
The FlexCut 125 requires 90–120 PSI input air pressure with a flow rate of 550 SCFH (260 SLPM) at 90 PSI. This is a substantially higher air demand than smaller plasma cutters — a rotary screw compressor is strongly recommended for sustained production CNC cutting at 125 A. A minimum of 20–25 SCFM at 125 PSI compressor output is appropriate for continuous single-machine operation. Industrial air treatment (moisture separator + coalescing filter) is required to protect LC125M consumable life. Nitrogen supply is required only for plasma marking mode — standard compressed air is used for all cutting operations.