Plasma cutters get sold on amperage numbers the way cars get sold on horsepower — impressive on paper, not always the number that matters for what you're actually doing. Buy too little power, and you'll be fighting slow, dross-covered cuts on anything beyond sheet metal. Buy way more than you need, and you've paid for capacity that sits unused while the machine's bulk and running costs work against you.

This guide sorts out what the amperage rating actually tells you, what duty cycle means in practice, and where people commonly overspend or underspend when kitting out a workshop or farm shed.

How Amperage Actually Determines What You Can Cut

The basic rule holds across almost every plasma cutter on the market: more amps means thicker material is cut cleanly and faster. A 30-40A machine handles material up to around 6mm comfortably. Push into the 45-60A range, and you're comfortably cutting 10-12mm. Get into 80A-plus territory, and you're looking at heavier industrial plate work, 20mm and beyond.

There's a difference between a machine's maximum cut and its clean cut rating, and manufacturers aren't always upfront about which number they're advertising. Maximum cut means the machine can physically get through the material, slowly and roughly. 'Clean cut' means a genuinely usable edge at a reasonable speed. If you're comparing two machines with the same amperage but very different prices, check whether the spec sheet is quoting max cut or clean cut — that gap explains a lot of the price difference.

Amperage	Clean Cut Thickness	Typical Use
30-40A	Up to 6mm	Light fabrication, farm repairs, hobby use
45-60A	Up to 12mm	General workshop, trailer and gate work
60-80A	Up to 16mm	Structural steel, heavier fabrication
80A+	20mm and above	Industrial plate cutting

A decent rule of thumb from the trade: buy a machine rated for roughly double the thickness you cut most often. If your day-to-day work is 6mm plate, a 60A machine gives you enough headroom to cut it fast and cleanly without constantly running the machine flat out.

Duty Cycle: The Number Everyone Ignores

Duty cycle tells you how long a machine can run at its rated output before it needs to cool down, expressed as a percentage over a 10-minute period. A machine rated 60% duty cycle at 40A means six minutes of cutting followed by four minutes of rest if you're pushing it at full amperage the whole time.

This matters enormously for anyone doing production work rather than occasional repairs. A cheap plasma cutter might list an impressive amperage figure but only manage a 20% duty cycle at that rating, which means constant thermal shutdowns the moment you're cutting more than a couple of pieces back to back. Farm and hobby use rarely pushes duty cycle limits. Fabrication shops running the machine most of the day absolutely will, so it's worth checking this figure specifically rather than assuming higher amps automatically means better performance.

Air Supply: Built-In Compressor or External Feed

Plasma cutting needs a steady supply of clean, dry compressed air to blow the molten metal out of the cut and cool the torch. Machines come in two flavours here.

Built-In Compressor Models

Genuinely convenient — plug in and go, no separate compressor to haul around or maintain. They suit smaller jobs and mobile work well, but they're limited in duty cycle and air volume compared to running off a proper external unit, and they tend to be noisier.

External Air Feed Models

Need a separate compressor supplying enough CFM (cubic feet per minute) and dry air, but they scale up to industrial cutting far better and don't struggle with continuous use the way a built-in unit can. Moisture in the airline is the enemy here — a cheap regulator or missing air dryer leads to pitted, rough cuts that look like a gas or amperage problem but are actually just wet air contaminating the arc.

Inverter Technology vs Older Transformer-Based Machines

Almost everything sold today is inverter-based, and there's good reason for that. Inverter plasma cutters are lighter, more portable, and more efficient than the older transformer-based machines, without giving up cutting performance. If you come across an older transformer-style unit secondhand, it'll likely be heavier and less efficient on power draw, though some tradespeople still swear by their durability. For most buyers in Ireland today, inverter technology is the sensible default rather than a premium upgrade.

Consumables and Running Costs

The upfront price of a plasma cutter is only part of the real cost. Nozzles and electrodes wear out with use, and cheap consumables wear out fast — sometimes fast enough that the savings on a budget machine evaporate within the first year of regular use. Before buying, it's worth checking how easily available and how priced the consumables are for a given machine, not just the machine itself. A slightly pricier cutter with cheap, widely stocked consumables often works out better value than a bargain machine with expensive, hard-to-find parts.

Common Mistakes People Make

Buying based on the highest amperage number without checking clean cut thickness or duty cycle. The headline figure looks great in an ad and tells you almost nothing about real-world performance.

Running a built-in compressor unit for extended production cutting and wondering why it keeps cutting out. That's the duty cycle limit doing exactly what the spec sheet said it would.

Skipping an air dryer or moisture trap on an external compressor setup, then blaming the machine for a rough, pitted cut that's actually a wet-air problem.

Wrapping It Up

The amperage number on the box is only the start of the story. Clean cut thickness, duty cycle, and how the machine handles air supply matter just as much for whether it'll actually suit your workload day to day. Match the machine to what you cut most often, not what you might theoretically cut once a year, and factor consumable costs into the real price before you buy.

If you're not sure which plasma cutter suits your setup, talk to our team before you buy. We stock plasma cutters across a full range of amperages and price points, along with MIG and TIG welders, welding helmets, and gas equipment for trade and hobby users across Ireland. Browse our plasma cutter range today, or give us a call and we'll help you match the machine to the job.

Plasma Cutters in Ireland: An Amps-to-Thickness Buying Guide

How Amperage Actually Determines What You Can Cut

Duty Cycle: The Number Everyone Ignores

Air Supply: Built-In Compressor or External Feed

Built-In Compressor Models

External Air Feed Models

Inverter Technology vs Older Transformer-Based Machines

Consumables and Running Costs

Common Mistakes People Make

Wrapping It Up

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