Cutting capacity is usually described in terms of clean cut and maximum cut thickness, and the two are worth distinguishing. Clean cut is the thickness a machine handles with a good edge finish and reasonable speed, while maximum cut is the thickest material the machine will get through at all, usually slower and with a rougher edge. Buying with your typical material thickness in mind, rather than the thickest job you might occasionally face, generally gives a better day-to-day result.
Shade range and sensor count are the two specifications that matter most in daily use. A wider variable shade range lets one helmet cover a broader spread of processes and amperages, from low-amp TIG work through to higher-output MIG or MMA, without swapping cartridges. More sensors generally mean the filter is less likely to miss a low-angle arc or a strike caught at an awkward viewing angle, which matters most for TIG welding where the arc can be harder for a sensor to pick up cleanly.
If you're still working out which process fits your workload, it helps to talk it through with people who field these questions every day rather than guess from a spec sheet, and the team behind TEC Products in Thirsk deal with exactly this kind of query on the advice line.
A reliable, adequately sized compressed air supply is the part most first-time buyers underestimate. Undersized or contaminated air, whether from moisture, oil or an undersized compressor, is one of the most common causes of poor cut quality and shortened consumable life, so it's worth checking a machine's air requirements against what your compressor can actually deliver before you buy, not after.
Before choosing a machine, it's worth checking what your workshop's consumer unit and incoming supply can actually handle, not just what socket is nearest the bench. Buying a three-phase-only machine for a single-phase workshop, or underestimating the load a higher-output single-phase welder places on existing wiring, are both avoidable problems with a bit of checking upfront.
Helmet choice comes down to the mix of processes you run and how much you're prepared to spend for extra sensors or a wider shade range, and it's a straightforward conversation to have with a stockist that carries several options, including TEC Products.