Start with the right material list.
Engineering material enquiries often depend on more than a nominal section size. A machine base may need a specific plate grade, while a machined pin may require a defined bar grade and finish. Distinguish general mild-steel fabrication stock from material that must meet an engineering drawing or machining requirement.
Plan before you order
Include the drawing reference and revision where appropriate. State whether supplied dimensions include a machining allowance, and list any test or inspection documents required before dispatch. Do not substitute a structural grade for a machining specification without approval from the responsible engineer.