Will this cutter handle larger diameter cables or just small gauge wire?

This is a general-purpose automotive cable cutter. Test-fit on your specific cable gauge before relying on it for production work — cutting capacity can vary based on material hardness and insulation thickness.

Can I use this for cutting brake lines or fuel lines?

This cutter is designed for electrical cable and wiring. Do not use on pressurized brake or fuel lines — that requires a specialized line cutter to prevent damage and contamination.

Does the blade need sharpening, or is it ready to use out of the box?

Ships ready to use. Over time, regular cutting dulls any blade. If cuts become ragged or require excessive pressure, hone or replace the cutting edge.