Machined weldments
Machined Weldments, Matched to Shops That Weld and Machine Under One Roof
Send one drawing. We match it with up to 3 suppliers that cut, weld, stress relieve and machine the part themselves, so the frame does not change hands halfway through. We reply within 24 business hours.
We are a matching service, not a fabrication shop. We own no machines and hold no welding certificates.
What you are actually buying
- Cut and preparePlate and tube cut to size, bevels prepared, holes left undersize where they will be bored later.
- Fit and tackParts set in a fixture and tacked. Fit-up decides the distortion you fight for the rest of the job.
- WeldMIG, flux cored, TIG or submerged arc, run to a written procedure with a defined sequence.
- Inspect the weldsVisual as standard, then dye penetrant, magnetic particle, ultrasonic or radiographic where the drawing calls for it.
- Stress relieveThermal or vibratory, before machining, so the frame moves in the oven instead of on the machine.
- MachineBores, mounting faces, rails and threads cut on a bed mill, horizontal boring mill or gantry, from datums that exist on the drawing.
- Finish and checkBlast, prime or paint with machined faces masked, then a dimensional report against the drawing revision.
Why buyers send machined weldment work here
It comes down to the match: shops that fit your part, from the first quote.
Matched by specialisation
Your drawing goes to up to 3 shops that weld and machine heavy structures in house, picked for your material, part size, weld quality level and machined tolerance. Not a general directory.
Professional suppliers
Shops in the network quote to your drawing, communicate clearly and keep you updated while your parts are made.
You deal with the shop
Quotes, terms and delivery are agreed between you and the shop. Free for buyers.
Is your part a machined weldment?
A machined weldment is a structure built from plate, tube or section, welded together, then machined where the tolerance has to hold. It sits between a casting and a part cut from solid, and it is the right answer more often than people expect on large, low volume work.
Tick what is true. The answer is worked out in your browser and goes nowhere.
Weldment, casting or machined from solid
The choice is usually decided by size and quantity before anything else. These are the trade-offs a quote will turn on.
Machined weldment
Plate and tube welded into shape, then machined where it matters.
- Best for
- Large, stiff, low to medium volume parts
- Tooling cost
- Fixtures only, no pattern and no die
- First part
- Weeks, not months
- Change cost
- Low. A design change is a new cut file and a new fixture
- Watch out for
- Distortion, residual stress and machining stock
Casting
Poured to near net shape, then machined on the critical faces.
- Best for
- Repeating volume and complex organic shapes
- Tooling cost
- Pattern or die, paid before the first part
- First part
- Months, including pattern and sample approval
- Change cost
- High. The pattern is changed or replaced
- Watch out for
- Porosity found only after machining opens the surface
Machined from solid
Cut out of one block or one thick plate.
- Best for
- Small parts, very tight tolerances, no weld allowed
- Tooling cost
- None beyond workholding
- First part
- Days
- Change cost
- Low, until the block size changes
- Watch out for
- Material cost and cycle time on anything large
The process chain, and where jobs go wrong
Every step below is a place a weldment gets expensive or gets scrapped. A shop that owns all of them can plan the sequence. A shop that owns half of it is managing a handoff.
| Step | What happens |
|---|---|
| Cut and prepare | Plate and tube cut to size, bevels prepared, holes left undersize where they will be bored later. |
| Fit and tack | Parts set in a fixture and tacked. Fit-up decides the distortion you fight for the rest of the job. |
| Weld | MIG, flux cored, TIG or submerged arc, run to a written procedure with a defined sequence. |
| Inspect the welds | Visual as standard, then dye penetrant, magnetic particle, ultrasonic or radiographic where the drawing calls for it. |
| Stress relieve | Thermal or vibratory, before machining, so the frame moves in the oven instead of on the machine. |
| Machine | Bores, mounting faces, rails and threads cut on a bed mill, horizontal boring mill or gantry, from datums that exist on the drawing. |
| Finish and check | Blast, prime or paint with machined faces masked, then a dimensional report against the drawing revision. |
Each step in detail, from cutting and welding processes to stress relief, machining and NDT: weldment fabrication processes.
Materials and what they do to the job
Grade changes the welding procedure, the preheat, the distortion and the machining. It is worth naming on the drawing rather than leaving to the shop.
| Material | Family | Typical use | What it changes |
|---|---|---|---|
| ASTM A36, S235JR | Mild structural steel | General frames, bases, brackets, guarding | Forgiving to weld and cheap to buy. Plate flatness out of the mill is loose, so allow stock on any face that gets machined. |
| ASTM A572 Gr 50, S355J2 | Higher strength structural steel | Machine bases, heavy frames, load bearing structures | Same welding processes as mild steel with tighter control on heat input. S355J2 carries an impact test at minus 20 degrees C, which matters if the drawing calls for it. |
| ASTM A514, S690QL | Quenched and tempered high strength steel | Booms, lifting structures, weight critical frames | Preheat and interpass temperature are controlled, not optional. Post-weld heat treatment can undo the temper, so the procedure decides what is allowed. |
| 304L and 316L stainless | Austenitic stainless | Food, pharmaceutical and chemical frames, skids, tanks | Moves far more than carbon steel for the same weld, and distortion control drives the fixture. Back purging and pickling or passivation are usually specified. |
| 6061-T6, 5083 | Aluminium | Light frames, robotic structures, marine parts | The heat affected zone loses strength in 6061-T6 and does not come back without re-treatment. Design so the weld is not the highest stressed section. |
| Hardox 400 or 450, AR400 | Abrasion resistant plate | Chutes, liners, buckets, crusher structures | Welded for wear life rather than for strength. Follow the plate maker preheat and heat input limits or the hardness at the joint is gone. |
| ASTM A500, EN 10219 tube | Structural hollow section | Frames, conveyor supports, gantries | Stiff for its weight and quick to fabricate. Corner radius and wall thickness tolerance decide whether a machined face on a tube is realistic. |
Standards you can specify against
These are public standards. Naming one on the drawing tells the shop what to build to and what will be inspected. This site holds none of them and does not certify anyone.
| Standard | What it covers | When it matters |
|---|---|---|
| AWS D1.1 | Structural welding code, steel | The default code for welded steel structures in North America |
| AWS D1.2 and D1.6 | Aluminium and stainless steel welding codes | Use these instead of D1.1 when the material changes |
| ISO 3834-2 | Quality requirements for fusion welding | What a shop has to have in place, not how a weld looks |
| EN 1090-2 | Execution of steel structures, classes EXC1 to EXC4 | Required for structural steelwork placed on the EU market |
| ISO 5817 | Weld quality levels B, C and D | The level you name decides which imperfections are accepted |
| ISO 13920 | General tolerances for welded constructions | Classes A to D on dimensions, E to H on straightness and flatness |
| ASME Section IX, ISO 9606-1 | Procedure and welder qualification | Evidence that the WPS and the welder were tested, not just written |
| ISO 2768, ISO 286 | General machining tolerances and fits | Applies to the machined features, after the weldment tolerances |
Tolerance after welding, not after machining
Welding moves metal. Everything below exists because the part you machine is not the part you drew, and the drawing has to say which condition each number applies to.
- Leave stock on every machined faceA common starting point is 3 to 6 mm on faces and 3 mm on the radius of a bore, and more on long or thin sections that are likely to move. Too little and the face cleans up in one corner only. Too much and the machining time doubles.
- Give the weldment and the machining separate tolerancesThe welded structure is normally held to an ISO 13920 class and the machined features to a normal drawing tolerance. Putting a machining tolerance on a welded dimension is the fastest way to a quote full of assumptions.
- Put the datums where the machine can reach themPick datum faces that will be machined and that a fixture can sit on. A datum on an as-welded surface moves with the distortion and every feature referenced to it moves with it.
- Say when flatness appliesFlatness and parallelism on a machine base are achieved after machining, not after welding, and they hold only if the part was stress relieved first. State the condition on the drawing so it is inspected the same way it was quoted.
- Decide about stress relief before you quote, not afterThermal stress relief for carbon steel typically runs at 580 to 650 degrees C with a soak of about one hour per 25 mm of thickness, plus controlled heating and cooling. It costs oven time and freight if the shop does not own an oven big enough.
- Name the inspection you wantVisual inspection of every weld is normal. Dye penetrant, magnetic particle, ultrasonic and radiographic testing each cost real money, so mark which welds get which method and at what rate rather than writing NDT on the title block.
What to specify, by part type
The general rules apply to every machined weldment. What changes is which of them dominates, and what the drawing has to say because of it.
Machine bases and frames
A machine base is the part every other tolerance in the machine is measured from. It carries the spindle, the rails and the drive, and it has to keep them in the same relationship under load, under heat and after a few years of vibration.
Conveyor and handling frames
A conveyor frame is a long, repetitive, relatively light structure where almost nothing is difficult except the one thing that matters: keeping features in line over a distance where a small angular error becomes a large linear one.
Gantries and robot pedestals
A gantry or a robot pedestal is bought to hold a position at the end of a reach. Everything about how it is specified follows from that, and almost none of it is about strength.
Process skids and baseplates
A process skid is a frame that carries pumps, drives, vessels and pipework so a plant can be assembled in a shop and installed in a day. The steelwork itself is rarely difficult.
Mining and wear structures
Mining structures are bought for wear life and impact resistance, and they are welded under constraints that do not apply anywhere else in fabrication.
Press and load bearing frames
A press frame is a structure that gets loaded, unloaded and loaded again, several million times. That single fact changes how it should be specified more than any material choice.
How it works
Three steps, no account to create, nothing to install.
Send your RFQ
Drawing, material, size envelope, the machined features and the quantity. Five minutes if the drawing is ready.
We match up to 3 shops
We check the size against their machines, the material against what they weld and whether machining and stress relief are in house. Shops that cannot take it never see your files.
Shops quote you directly
You compare the quotes, ask your own questions and order from the shop you pick. Nothing passes through us and we take no commission.
What drives the price
Weldment quotes vary more between shops than machined parts do, because each shop prices its own bottleneck. These are the lines that move.
Plate grade and thickness
High strength and abrasion resistant plate cost more per kilogram and are slower to cut, bevel and weld. Thickness drives weld volume, which drives almost everything downstream.
Weld length and joint preparation
Total weld length and whether the joints are fillets or prepared full penetration welds. A full penetration joint needs a bevel, more passes and usually an inspection method.
Weld quality level and inspection
ISO 5817 level B on every joint costs far more than level C where it matters and level D elsewhere. Ultrasonic and radiographic testing add a supplier, a report and a few days.
Stress relief
Oven time, handling and freight if the shop does not own an oven that fits the part. It is cheap compared with scrapping a machined frame that moved.
Machining envelope and setups
Whether the part fits one machine in one setup. Every re-fixture on a heavy weldment is hours of crane time and a new alignment, and it puts tolerance at risk.
Flatness, parallelism and bore position
Tight geometric tolerance across a long part means slower cuts, more measurement and sometimes a second pass after the part relaxes.
Coating and masking
Blast, prime, paint or galvanising, plus masking every machined face and thread. Galvanising after machining will move the part, so the sequence has to be decided at quote time.
Weight and freight
Weldments are heavy and bulky. On a large frame the transport line can rival the machining line, which is why supplier region is a real question and not a preference.
Everything we know, published
Free, no email gate, and useful whether or not you ever send us a drawing. If it is good, that tells you something about whether we understand the part.
Every term on a weldment drawing
Filterable definitions for the vocabulary that shows up on drawings, quotes and inspection reports.
ChecklistWeldment RFQ checklist
Everything a shop needs before it can quote without assumptions. Printable, and the ticks never leave your browser.
CalculatorMachining allowance
A defensible starting range for the stock to leave, from part size, weld density, material and stress relief.
ReferenceSymbols, tolerance classes, steel grades
How the class systems relate and which standard governs what, without republishing tables we do not own.
How we research this, what we will never claim and how to report an error are all written down on the editorial standards page. How we get paid is on the about page, in full.
Send the drawing
A few lines and a file are enough to start. If you would rather fill in the full specification now, the complete RFQ form asks about weld quality, inspection, stress relief and machined tolerances, which is what a shop needs to quote without a second email.
We reply within 24 business hours, including to say we cannot help.
Become a partner shop
If you weld and machine heavy structures in the same building, you can see these requests. Preview each one before you pay for it, then quote the buyer directly. No subscription and no commission on the order.
Questions buyers ask
Do you weld and machine the parts yourselves?
No. We are a matching service, not a fabrication shop and not a machine shop. We read your RFQ and pass it to suppliers that already weld and machine this kind of part. They quote you directly and you place the order with the one you pick.
Is this free for buyers?
Yes. Sending an RFQ and receiving quotes costs you nothing. Suppliers pay us for matched requests. Price, terms, inspection scope and delivery are agreed between you and the supplier.
Who sees my drawing?
Suppliers first see a short preview: part type, material, size envelope, weight, quantity, weld quality level, inspection scope and region. It does not carry your name, your company or your files. Your contact details and files go only to the shops we match, up to 3. If you ask for an NDA we hold the files until it is signed.
Do the matched shops machine in house or subcontract it?
We ask every shop at registration which machining equipment it owns, the travels of each machine and whether stress relief and inspection are in house or bought in. That answer goes on the match so you know before the quote whether the part leaves the building between welding and machining.
How large a weldment can be handled?
Say the overall envelope and the finished weight in the RFQ and we match against machines that actually take it. Size is the first thing that rules a shop out, because a frame can be welded far larger than it can be machined in one setup.
Does my part need stress relief before machining?
It depends on how much weld metal went in, how thick and restrained the joints are and how tight the machined features have to stay. Heavily welded frames with bores or mounting faces that must hold position are normally stress relieved before finish machining. If you are not sure, say so in the RFQ and let the quoting shops tell you what they would do and what it costs.
What should I send with the RFQ?
A STEP file plus a PDF drawing with weld symbols, the material and grade, the weld quality level or the standard you want the welds judged against, any non-destructive testing, which faces and bores are machined and to what tolerance, the finish and the quantity. Weldments quoted from a model with no weld symbols get re-quoted later, usually higher.
Latest guides
- Process
Oct 18, 2026Lamellar Tearing and Z-Grade Plate in Weldments
Lamellar tearing in thick plate T and corner joints: cause, Z15 Z25 Z35 through-thickness grades to EN 10164, design fixes and what to specify on the drawing.
- Tolerances
Oct 17, 2026Hydraulic Press Frames as Machined Weldments
Press frame weldment guide: C-frame and four-post designs, deflection targets, thick plate welding, stress relief, machined faces and cylinder bores, and RFQ content.
- Process
Oct 16, 2026Horizontal Boring Mill Machining for Large Weldments
How horizontal boring mills machine large weldments: table and floor types, spindle reach, rotary table indexing, setup count and what to ask a shop at quote stage.