SAE/AISI 3135, equivalent to DIN/EN 36NiCr6 (Wnr. 1.5710), is a nickel-chromium low-alloy engineering steel from the historic "31xx" series. Nickel improves core toughness and impact resistance beyond what a plain carbon steel of similar strength can offer, while a modest chromium addition contributes hardenability. Its carbon content — roughly 0.32–0.40% — puts it above the range typically used for carburizing steels, so despite superficial family resemblance to lower-carbon Ni-Cr case-hardening grades, 3135/36NiCr6 is more accurately classified as a through-hardening engineering steel: it is supplied and machined in the annealed or normalized condition, then quenched and tempered to raise strength in the finished part rather than carburized to build a hard surface case.

That combination of moderate carbon with nickel-chromium alloying makes 3135 a practical choice for medium-strength structural and mechanical components that need better toughness than a plain carbon steel provides without the cost and complexity of a heavier Cr-Mo-Ni grade like 4340. Typical applications include connecting rods, bolts, arbors, pins, and axle arms — parts that see cyclic loading and benefit from nickel's contribution to fatigue and impact resistance.

In the annealed or normalized condition most shops receive it in, 3135/36NiCr6 machines reasonably well — nickel adds a degree of gumminess and toughness compared with a plain carbon steel at the same hardness, which raises cutting forces somewhat and can encourage built-up edge at low speeds or with a dull tool, but the alloy content here is far lighter than in heavier Ni-Cr-Mo grades. Chromium contributes some fine carbide formation that adds mild abrasive wear, though nowhere near the level seen in higher-chromium alloy or tool steels.

Chip formation is generally continuous to segmented and controllable with standard chipbreaker geometry in the annealed state. As with other nickel-alloyed steels, staying within the recommended speed range and keeping the edge sharp helps avoid the smeared, dragging chip that low speeds and a worn edge can produce on tougher alloy steels.

Because many parts made from this grade are quenched and tempered after rough machining to reach final strength, dimensional stock allowance for heat-treatment distortion is a practical consideration alongside tool selection. A coated carbide grade with a good balance of wear resistance and edge toughness handles the nickel-chromium alloy content well without sacrificing surface finish.