Precision Sheet Metal Fabrication Services & Specification Guide

This page is an educational specification guide drawn from the preserved record of E.C. Hilliard Company and Hilliard Precision Products, LLC. It is not a live vendor page and does not offer current quoting or services.

What a Fabricated Assembly Specification Must Establish

A sheet metal fabrication specification is the written agreement between design intent and shop practice. It tells the fabricator what the part must be, how it must be made, and how it will be inspected. The preserved history of E.C. Hilliard Company, founded in 1903, and its successor Hilliard Precision Products, LLC, records a tradition of precision metal fabrication guided by uncompromising integrity and quality workmanship. That tradition is a useful frame for specification: quality begins with design and engineering, before any material is cut.

A complete specification addresses five linked decisions. First, material and gauge, including alloy, temper, and thickness tolerance. Second, the flat pattern, meaning the developed blank size, bend deductions, and grain direction. Third, bend radius and bend sequence, which determine whether the part forms without cracking or interference. Fourth, the weld and fastener schedule, which fixes joint type, weld size, placement, and hardware callouts. Fifth, finish, including surface preparation, coating, and masking. Each decision constrains the others, so the drawing should present them together rather than as separate notes.

The historical record notes that Hilliard Precision Products, LLC invested in advanced equipment, including a Trumpf B 200 press brake, a V855 press brake, an HE&M saw, Global Shop ERP software, a robotic welder, and automated large-capacity laser cutting. A Bystronic 3500-watt laser was described as the largest and fastest laser in New England at the time, with a fully automated load and unload cell and a 5-foot by 10-foot sheet capacity, cutting from 0.10-inch shim stock to 7/8-inch plate at speeds up to 280 inches per minute. These details illustrate why the specification must match the process: a blank developed for one machine and tooling set may not transfer cleanly to another.

Material and Gauge: The First Constraint

Material selection sets the forming window. Mild steel, stainless steel, aluminum, and coated steels behave differently in bending, welding, and finishing. Gauge callouts should be explicit: state the nominal thickness and the governing tolerance rather than relying on a gauge number alone, because gauge tables vary by material and standard. Where the design permits, specify a standard sheet size that nests efficiently on the available cutting bed. The preserved record describes a 5-foot by 10-foot sheet capacity, which is a practical planning envelope for flat patterns.

Grain direction matters in aluminum and in some stainless grades. A bend placed across the grain behaves differently from one placed along it. If the design is sensitive to cracking or springback, note the required grain orientation on the drawing. Also state the temper or condition, since soft tempers form more readily but may not hold tolerance after welding. Incoming material inspection was part of the quality process recorded in the archive, beginning with design, engineering, and incoming materials. A specification that names the material standard and the inspection expectation supports that sequence.

Flat Pattern, Bend Radius, and Bend Sequence

The flat pattern is a derived geometry, not a guess. It depends on the bend deduction or K-factor appropriate to the material, thickness, tooling, and inside radius. The drawing should state the inside bend radius or the preferred tooling radius, and it should identify critical dimensions that must be held after forming. Where a dimension is reference only, mark it as such so the fabricator does not over-constrain the blank. A well-developed flat pattern also accounts for bend relief at corners and for clearance around holes near bend lines.

Bend sequence controls distortion. Every bend redistributes residual stress, and the order of operations determines whether a part closes square or walks out of tolerance. A practical sequence forms the most constrained bends first, then progresses to bends that are free to move. Bends near a weld joint are usually formed before welding, because weld heat relaxes the formed shape. Where a part requires a hem or a tight radius, sequence that operation after the adjacent bends so the tooling has clearance. The drawing should include a bend table with direction, angle, radius, and sequence number, and it should flag any bend that must be made in a specific order.

Springback is the visible symptom of an incomplete specification. It varies with material, thickness, radius, and tooling. Rather than specifying a single angle without tolerance, state the acceptable angular tolerance and identify which bends are cosmetic and which are functional. The archive records press brake equipment including a Trumpf B 200 and a V855, which indicates that the shop planned around controlled forming rather than hand adjustment. A specification that names the forming intent helps the fabricator choose tooling and compensation.

Weld and Fastener Schedule

Welding is where distortion becomes most visible. Heat input, joint fit-up, weld size, and weld sequence all contribute to movement. The specification should define the weld process, the joint type, the required throat or leg size, and the inspection method. It should also state whether welds are continuous or intermittent, and whether they are structural or sealing. Cosmetic welds should be called out separately, because grinding and blending add cost and can thin the base material.

Weld sequence is a distortion-control tool. Balanced welding, back-stepping, and alternating sides distribute heat more evenly. Tack welds should be placed to hold alignment without locking in stress. Where a fabricated assembly includes machined inserts or purchased components, the weld schedule should identify the order of assembly so that heat does not damage finished features. The archive notes a robotic welder among the equipment, which supports repeatable weld placement when the schedule is explicit. Fasteners deserve equal clarity: specify thread size, class, material, plating, and installation method, and note whether hardware is installed by the fabricator or supplied by the customer.

The preserved record describes a quality system that treated quality as integral to every step of every project, beginning with design, engineering, incoming materials, and tool calibration. A weld and fastener schedule that names inspection points follows that logic. It also prevents ambiguity at the bench, where a missing callout is often resolved by habit rather than by design intent.

Finish, Distortion Control, and Drawing Package

Finish specification should state the coating system, color, gloss, and any masked areas. Surface preparation matters: welds that will be painted must be cleaned and dressed to the specified profile. Where parts are formed after coating, the coating must tolerate the bend. Where parts are coated after assembly, the specification should identify threads and mating surfaces that must remain free of coating. The archive records ISO 9001:2000 status with quality manuals available upon request, which reflects a documented approach to process control rather than an ad hoc one.

Distortion control is a system, not a single note. It combines material selection, flat pattern development, bend sequence, weld sequence, and fixturing. A drawing that specifies all five gives the fabricator a coherent plan. A drawing that omits them invites rework. The most common omissions are bend sequence, weld size, and the distinction between reference and critical dimensions. Each omission shifts a design decision to the shop floor, where it may be made without full knowledge of the assembly's function.

Before requesting a short-run quote, assemble a drawing package that includes the flat pattern or the formed model, the bend table, the weld and fastener schedule, the finish specification, and the inspection criteria. Include the material standard and thickness tolerance, the required quantities, and any known constraints on tooling or process. State which dimensions are critical and which are reference. This package does not constitute a quote request on this page, and this archive does not offer current quoting or services. It is simply the information a fabricator needs to evaluate a short-run job accurately.

The historical record of E.C. Hilliard Company and Hilliard Precision Products, LLC is preserved here as a reference for specification practice. The company was founded in 1903 and built a reputation for achieving demanding fabrications at the lowest possible cost, guided by integrity and quality workmanship. On May 18, 2006, E.C. Hilliard Corporation was purchased by Sanweld Industries of Worcester, Massachusetts, and the name was changed to Hilliard Precision Products, LLC, bringing together the former divisions: Van Noorden Company, Van Noorden Gate Systems, Van Noorden Detention Equipment, and Allcraft Marine Water Heaters. That record is offered here for its historical and educational value, not as a claim of current capability or successor status.