AISI/SAE 1144 is the highest-sulfur grade in this group of resulfurized free-machining steels, combining a solid 0.40–0.48% carbon content and elevated 1.35–1.65% manganese with sulfur pushed all the way up to 0.24–0.33%. That's roughly double the sulfur level of a moderately resulfurized grade like 1140, and it produces a dense population of manganese sulfide inclusions that make 1144 exceptionally easy to cut for a medium-carbon steel. In the trade, cold-drawn and stress-relieved bar of this grade is often sold under proprietary names like "Stressproof," prized for the combination of high machinability with genuinely good strength, hardness, and surface finish straight off the bar.

Because it holds onto real mechanical properties despite the high sulfur content, 1144 is a go-to grade for parts that need both fast, clean machining and solid fatigue strength without any additional heat treatment — shafts, spindles, hydraulic rods, studs, and other precision-turned components produced in volume. As with all resulfurized steels, the sulfur addition reduces transverse ductility, impact toughness, and weldability, so 1144 is chosen specifically for machined, non-welded applications where its strength-to-machinability ratio is the main draw.

1144's very high sulfur content, combined with its elevated manganese, produces one of the most effective chip-breaking microstructures in the carbon steel family. The abundant manganese sulfide inclusions give the material a built-in fracture path, so chips break consistently short even at aggressive feeds, cutting forces stay lower than a plain 1045-type steel of similar carbon content would require, and the risk of built-up edge is greatly reduced because the inclusions limit metal-to-metal contact at the tool-chip interface.

What sets 1144 apart from lighter-sulfur grades is that it delivers this machinability without sacrificing much strength — the higher manganese content supports good hardenability and fatigue strength, so parts machined from 1144 don't need to compromise on mechanical performance the way some free-cutting grades do. That combination is exactly why cold-drawn 1144 bar is favored for precision shafts and rods that need both a fast lathe cycle and solid in-service strength.

From a tooling standpoint, 1144 rewards positive-rake coated carbide grades and can generally run at higher cutting speeds than a plain medium-carbon steel of comparable hardness. Chip control is rarely an issue on this grade even at high feed rates, so the main focus for tool selection is matching coating and substrate to the target surface finish and expected production volume.