Fabrication & Welding Shops

The machined half of a weldment

Most weldments carry a handful of features that no fabrication process puts there: a bored and reamed bushing seat, a turned boss that has to run true to a shaft, a pin that indexes two plates, a tapped pad on a surface that has to end up flat. Those are the parts quoted here. You keep the cutting, forming and welding; the machined details come back to your print, ready to drop into the fixture.

The welding side is documented separately. The American Welding Society publishes separate structural welding codes by base metal, among them D1.1 for steel, D1.2 for aluminum, D1.3 for sheet steel and D1.6 for stainless (source 1). Your weld procedure stays yours. The machined feature is dimensioned on your print and quoted from it.

There is no minimum. A set of six bushings for one weldment is quoted the same way as a hundred for a run of frames.

Why the machined detail goes in rather than being welded up

Aluminum is the clearest case. After welding, the properties of 6061-T6 near the weld are those of 6061-T4, a loss of strength of around 40% (source 2). The Aluminum Design Manual, as Wikipedia reports it, recommends taking the design strength of the material next to the weld as 165 MPa (24,000 psi) without proper heat treatment after welding, against a T6 ultimate tensile strength of at least 290 MPa (42 ksi) (source 2). A detail that carries a bearing load is one to weigh for machining from solid and pressing or bolting in rather than welding on as a pad. How the joint is designed stays with you.

Sheet aluminum behaves differently. Wikipedia describes 5052 as not heat treatable but hardened by cold working, lists 5052-H32 at 228 MPa (33,000 psi) ultimate and 193 MPa (28,000 psi) yield, and rates its arc weldability very good (source 3).

Steel is more forgiving. A36 plate, bar and shapes under 8 in thick have a minimum yield strength of 36 ksi (250 MPa) and an ultimate tensile strength of 58-80 ksi (400-550 MPa), and Wikipedia says A36 “is readily welded by all welding processes” (source 4). Because A36 welds readily, the reason to machine a steel detail tends to be geometry: a bore that has to be round and located, a face that has to be flat, a thread that has to be full depth.

Machining after welding: one order, made, welded, then machined

Machining after welding is quoted when the whole job is one order: the parts are made, welded, then machined, as on laser cut and welded parts. A weldment you built and send in is not machined. For the weldments you build, what is quoted is the machined and turned details that go into them. On a one-order job, the weldment drawing marks the post-weld features, says which datums are established after welding rather than before, and gives the stock left on each machined surface.

Welding moves metal. Residual stresses left as a weld cools often lead to distortion or warping during machining, assembly and later use (source 5), and low-rigidity welded structures tend to distort after welding (source 6). That is the case for machining the features that have to hold after welding, so on a one-order job the print should say what moves and what has to hold: which faces get machined after welding and which are as-welded, the bore diameter and fit class on anything that takes a bearing or bushing, whether flatness is called out across the whole plate or per pad, and whether the assembly has been stress relieved.

AWS A2.4, Standard Symbols for Welding, Brazing, and Nondestructive Examination (source 7), establishes a method for specifying welding information by means of symbols. If the machined callouts are on the same sheet as the weld symbols, the quote is read from one drawing.

Blanks past your table, cut and finished as one order

The second reason a fabrication shop buys out is size or thickness. When a job calls for a run of blanks past what your own table handles, or for a material you do not stock, the profile is cut and the secondary work goes on the same order: tapped and countersunk holes, bends, pressed-in hardware and a finish. Name the material and thickness on the print. The inside radius is quoted as drawn, with a note if it won’t form. A finish called out on the print is quoted with the part. That is laser-cut parts, and the way the operations stack onto one order is set out on laser cut, tapped and machined as one order. Laser work is quoted per job, rush available.

Two spokes are worth naming for a fabricator: plates and spacers for flat stock with holes in it, and laser-cut and bent brackets when the part is formed rather than flat. If the bracket is heavier or needs features a brake cannot hold, it moves to machined brackets instead.

One purchase order for the part you are not making

The paperwork is the other half of buying out. Vendor setup takes a day: W-9, NDA, net terms available, with one contact from quote to delivery and no portal. A quote comes back in 24-48 hours whether the package is one turned bushing or a mixed order of machined details, laser-cut blanks and a weld fixture. Machined lines follow the three delivery tiers. Rush: 1-2 weeks. Standard: 4-6 weeks (typical). Extended: 6-8 weeks, for jobs that aren't time-sensitive. Rush is quoted at a premium. Rush 1-2 weeks applies to machined parts with no secondary operations. Heat treat, grinding, EDM and finishing add time, and the quote gives the real date. Lead time starts at order approval. Put your need date in the part description and the quote answers it. Every part inspected against your print before it ships.

No C of C or material certifications ship with parts by default. If your PO needs them, say so before the quote. Inspection reports on critical dimensions aren’t included by default. If you need one, ask when you place the order. Everything about how a job is bought here is on machined parts supplier, and if the drawing work is what you are short on, overflow engineering support is quoted per task.

Sources

All accessed 4 October 2026. Where a figure here differs from your print, the print governs.

1. Wikipedia, "List of welding codes": en.wikipedia.org/wiki/List_of_welding_codes (AWS D1.1 structural welding of steel, D1.2 aluminum, D1.3 sheet steel, D1.6 stainless steel).

2. Wikipedia, "6061 aluminium alloy": en.wikipedia.org/wiki/6061_aluminium_alloy (after welding, properties near the weld are those of 6061-T4, a loss of strength of around 40%; Aluminum Design Manual design strength next to the weld 165 MPa / 24,000 psi; T6 ultimate tensile strength at least 290 MPa / 42 ksi).

3. Wikipedia, "5052 aluminium alloy": en.wikipedia.org/wiki/5052_aluminium_alloy (not heat treatable, hardened through cold working; H32 ultimate 228 MPa (33,000 psi), yield 193 MPa (28,000 psi); arc weldability very good).

4. Wikipedia, "A36 steel": en.wikipedia.org/wiki/A36_steel (minimum yield 36 ksi (250 MPa) under 8 in thick; ultimate tensile strength 58-80 ksi (400-550 MPa); readily welded by all welding processes).

5. Wikipedia, "Vibratory stress relief": en.wikipedia.org/wiki/Vibratory_stress_relief (residual stresses often lead to distortion or warping of the structure during machining, assembly, transport, field use, or over time).

6. Horajski, Bohdal, Kukielka, Patyk, Kaldunski and Legutko, "Advanced Structural and Technological Method of Reducing Distortion in Thin-Walled Welded Structures," Materials (Basel), 2021, 14(3):504: pmc.ncbi.nlm.nih.gov/articles/PMC7864496/ (low rigidity structures tend to distort after welding).

7. American Welding Society, "A2.4:2020 Standard Symbols for Welding, Brazing, and Nondestructive Examination": pubs.aws.org/p/1999/a242020-standard-symbols-for-welding-brazing-and-nondestructive-examination (a standard that establishes a method for specifying welding, brazing and nondestructive examination information by means of symbols; referenced, not reproduced).