ASTM A570 is a specification for hot-rolled carbon steel sheet and strip covering six strength levels — Grades 30, 33, 36, 40, 45, and 50 — each carrying its own minimum yield and tensile requirement. This page covers Grades 33 and 36, two of the lower-strength tiers in the family, which are frequently supplied and specified together because their mechanical requirements sit close to one another: Grade 33 calls for a 33 ksi (230 MPa) minimum yield and 52 ksi (360 MPa) minimum tensile strength, while Grade 36 steps up slightly to a 36 ksi (250 MPa) minimum yield with a 53 ksi (365 MPa) minimum tensile strength.

Like the rest of the A570 family, these grades are plain carbon-manganese steels with no significant alloy additions, formulated for good formability rather than maximum strength. That makes them a natural fit for parts that need to be roll-formed, bent, or stamped into shape without cracking — light structural framing, enclosure panels, brackets, guardrail components, and general sheet-metal fabrication where the part geometry matters more than pushing for extra load capacity. Where a design calls for higher strength in the same A570 family, Grade 50 (covered on a separate page) is the better fit.

Because these are among the softest, most ductile grades in the A570 range, they're also the easiest to form into tight radii and complex profiles. Shops encounter this material primarily as coil or sheet stock that gets formed first and then trimmed, drilled, or edge-finished afterward, rather than as bar stock turned on a lathe.

Grades 33 and 36 are about as soft and ductile as structural sheet steel gets, which cuts both ways in the shop. Cutting forces and power demand are low, and tool life is rarely the limiting factor — but low carbon content also means the material doesn't shear into short, well-broken chips on its own. Chip control depends almost entirely on chipbreaker geometry, so pairing the right insert geometry with the operation matters more here than on higher-carbon or alloyed material.

Built-up edge is the dominant failure mode at low cutting speeds: soft material smears across the rake face instead of shearing cleanly, then tears off unevenly and leaves a poor finish. Running toward the upper end of the recommended speed range, keeping feeds high enough that the tool is always cutting rather than rubbing, and using a sharp, positive-rake edge all help avoid it.

Because this material typically arrives at the machining step already formed into sheet-metal parts, most shop operations are drilling, tapping, edge-trimming, and light face work rather than heavy turning. Sharp cutting edges and adequate flute clearance make a bigger practical difference in part quality than raw spindle speed — a dull edge on this material drags and burrs rather than cutting cleanly, which is immediately visible on a finished formed part.