Press Brake Basics: Getting Tonnage and Bed Length Right

A press brake is sized by two numbers: how hard it can push (tonnage) and how wide it can bend (bed length). Get either wrong and you own the wrong machine.

The tonnage rule of thumb

For ordinary mild steel with standard V-die air bending, you need roughly 8 tons per metre for every millimetre of thickness. Bending 3 mm steel across 3 metres calls for about 72 tons; 6 mm across the same width jumps past 280 tons because force rises with the square of thickness. Stainless needs about half again more; aluminium about half less.

Bed length and real-world checks

Buy the bed for the widest part you actually make, not the widest you can imagine — a 3.2 m machine that is always half empty wastes floor space and electricity. On a used machine, check the ram for daylight against a straight edge, listen to the hydraulics under load, and bend a test piece at both ends and the centre: uneven angles reveal a worn ram or crowning problem faster than any spec sheet.

A correctly sized used press brake from a reputable maker will outlast several changes of your product line — which is why the used market for them is so healthy.