British Columbia
HOW TO CHECK AND SIGN OFF THE FIRST PART OF A RUN
A first article inspection checks one part against the whole drawing, and the part you approve sets the standard for the run
A first article inspection checks the first part made against every dimension and note on the drawing. It happens before the rest of the run is made. Aerospace made it a formal standard, and the same regulation protects any bracket, guard, or panel you reorder. You number the drawing, measure each numbered item, and fit the part on the machine it's made for. Then you sign the results and keep the approved part as the signed sample. This guide covers when you need one, where sheet metal parts tend to go wrong, and what the sign-off sheet should record.
A full check makes sense whenever something about the design or the way it's made is new. An unchanged reorder from the same shop needs much less.
| Your situation | Check to ask for | Why |
|---|---|---|
| A part nobody has made before | A full first article inspection | Nothing about the drawing or the setup has been proven in metal yet |
| A drawing change that affects how it fits or works | A check of the dimensions the change touched | The rest of the design is already proven, so only the new features need measuring |
| The same part from a new shop, a new machine, or a new metal | A full first article inspection | A different machine or metal can bend, stretch, or finish the part differently |
| A part that hasn't been made for two years | A fresh check of every dimension the gap could affect, or a full one if you can't tell | Machine programs, tooling, and staff can change over two years, so the aerospace standard, AS9102, asks for a fresh check |
| A steady reorder of an unchanged part from the same shop | A first piece check by the shop | The design is proven, so measuring the few dimensions that decide fit catches a mistake in how the machine was set up |
| A cover or panel your customers will see | A finish sample signed alongside the first part | The look of a brushed or painted surface is easier to agree on with a sample in hand |
If your order fits more than one row, go with the bigger check. The step before this one, deciding whether you need a prototype at all, is covered in Sheet Metal Prototype to Production.
Three terms get mixed up because they all involve an early part from the run. Each answers a different question, and a repeat order usually needs all three at some point.
Every dimension and note on the drawing is measured and written down during a first article check. You sign the results. It's done in full once, then repeated after a change or a long gap, in full or only on what changed.
Each time the machines are set up for a new batch, the first part off them is measured on its critical dimensions. A setup mistake gets caught before the whole batch repeats it.
Tag the part you approved and keep it on your own shelf. If a later batch looks or fits differently, hold the two side by side.
Aerospace suppliers write the full checkup on three standard forms under SAE AS9102. One form covers the part number, one the material and processes, and the third lists every dimension. A sheet metal order rarely needs those forms, but any sign-off should still record all three.
A full check is only full if every dimension gets measured. Numbering the drawing first turns the drawing into a list you can tick off.
Number every dimension and note. Put a circled number beside each one on a copy of the drawing. Quality teams call this a ballooned drawing.
Mark the critical dimensions. These are the few where a small error stops the part from fitting or working, such as a bolt pattern.
Measure each numbered item. Write the reading next to its number, with the tool you used.
Compare each reading with what the drawing allows. The drawing gives the size and how far it may vary, called the tolerance.
Flag anything outside its range. Decide what happens to each one before anyone signs.
Number every dimension, then give each number a reading
Bracket BR-120, a separate illustration from the conveyor bracket example. Critical dimensions have a star.
The drawing, numbered
Datum A is the left edge, datum B the top edge
Holes 3 to 5 are the bolt pattern, hole 5 near the bend
The results sheet
| No. | Feature | Allowed | Reading | Result |
|---|---|---|---|---|
| 1 | Overall width | 200 ± 0.5 | 200.2 | Pass |
| 2 | Height to bend | 120 ± 0.5 | 119.8 | Pass |
| 3 | Hole 3 from datum A ★ | 30 ± 0.2 | 30.1 | Pass |
| 4 | Hole 4 from datum A ★ | 170 ± 0.2 | 170.0 | Pass |
| 5 | Hole 5 from datum B ★ | 100 ± 0.2 | 100.6 | Out |
| 6 | Slot length | 40 ± 0.3 | 40.1 | Pass |
| 7 | Bend angle | 90° ± 1° | 90.5° | Pass |
Sizes in millimetres. Decide what happens to hole 5 before anyone signs.
Illustration, not a real part.
Most first-part problems on sheet metal show up in the same six places. Check these before anything else, starting with the bends.
| Feature | What can go wrong | How to check it |
|---|---|---|
| Dimensions measured across bends | Each bend adds its own small variation, so a size across three bends varies more than one between two cut edges | Measure every size that crosses a bend, against the tolerance the drawing gives that size |
| Holes and slots close to a bend | The metal stretches in the bend and can pull a nearby hole out of round or out of place | Check each hole near a bend for shape and position, and try the bolt that goes through it |
| Hole positions | A hole can be the right size and still sit in the wrong spot | Measure each hole from the edge or hole the drawing measures from, called a datum, not from whichever edge is closest |
| Threaded inserts and studs pressed into the sheet | An insert pressed in close to a bend, especially before the bend is made, can loosen or hold less | Thread in the fastener your assembly uses and tighten it to its torque |
| Paint or powder coat | A thick coat can close up a tight slot or stop two parts fitting together | Have the coating thickness measured with a coating gauge, and test the fit after coating |
| Grain on brushed stainless | The brush lines can run the wrong way on a panel that sits beside others | Compare the grain direction with the drawing and with the parts it will sit next to |
A datum is the edge, face, or hole a drawing measures everything else from. On many drawings it's marked with a capital letter in a small box, such as A. Measure each hole from the same datum the drawing uses. Start from another edge, and a hole in the right spot can look wrong, while a wrong one looks right.
A part can match every number on the drawing and still clash with something the drawing doesn't show. A short test on the machine finds the clash before the whole batch is made.
Write the result of each test on the sign-off sheet, along with the measurements.
The sign-off sheet is what you and the fabricator point to on every later order. It works when someone who wasn't there can read it and know exactly what was approved.
| What goes on the sheet | Why it's there |
|---|---|
| Part number and revision letter, the letter on the drawing that marks its version | It ties the approval to one version and no other |
| Metal, thickness, and finish as made | A later batch in a different metal or coat isn't covered by this approval |
| Each numbered dimension, its allowed range, and the reading | It shows every dimension was measured, not only the easy ones |
| The fit and function test results | It records that it works on the machine, not only on the bench |
| Anything you accepted that differs from the drawing | Accepting a difference in writing covers this run without quietly changing the drawing |
| Who signed it, and where the signed sample is kept | The next person knows who approved it and where to find the reference part |
Keep a copy with your purchasing records. Send another with each order, so both sides work from the same sheet.
A measurement outside its tolerance costs least to fix on the first part, before the rest are made. Settle it before the run starts, and write down which way you chose.
If the part is wrong and the drawing is right, the first part is made again and checked. If the mistake was ours, we remake it at no charge.
If the difference doesn't affect fit or function, you can accept it for this run only. Write it on the sign-off sheet, and the next run goes back to the drawing.
If the part works better as made than as drawn, update the drawing instead. It takes a new revision letter, and every later order follows it.
Revision Control on Repeat Parts explains how a drawing change gets its letter, and when it needs a new part number instead. A part that arrives wrong on a delivered order follows a different path, covered in What Happens When Wrong Parts Are Delivered to Your Job.
Equipment makers often ask suppliers to keep one approved part for the life of the product. A sheet metal buyer gets the same benefit by keeping the signed sample on their own shelf.
If a later batch looks or fits differently, you can hold the two side by side. A sample in hand settles questions a drawing can't.
Label the sample so it can't be mistaken for an ordinary spare. If it gets used on a machine, the reference is gone.
If the look matters, keep one piece at the edge of what's acceptable, called a limit sample. Then any later panel can be judged against both.
If the revision letter moves on, sign a new sample for it. Label the old one as replaced, so no new batch gets compared against it.
This example shows a full check and a drawing fix on one bracket. The bracket and its readings are an illustration, not a customer's order.
| Step | What happened | Result |
|---|---|---|
| 1. The drawing | A conveyor maker numbers 14 dimensions on a bracket drawing, revision A, and marks the 4 bolt holes as critical | A list of 14 items to measure |
| 2. The measurements | All 14 readings sit inside their tolerance, including the slot near the bend | The bracket matches its drawing |
| 3. The fit test | On the conveyor, the slot sits 3 mm short of where the frame's bolt lands | The drawing is wrong, not the bracket |
| 4. The decision | The maker moves the slot on the drawing, now revision B | Only the slot needs checking on the next first part |
| 5. The sign-off | The revision B bracket bolts on cleanly, and the slot measures inside its tolerance | Signed, tagged, and kept as the sample for every reorder |
Step 3 is why you test the part on the machine as well as measuring it. Marking the slot as critical in step 1 would have given it the closest look.
New parts are cut, formed, welded, and assembled on our floor in Pitt Meadows. Each one runs through the same checks before it reaches you.
We read the drawing first. We confirm the revision letter, the tolerances, and which dimensions matter most, and ask about anything unclear before quoting.
We make the first part. It's shaped through our cutting and bending work, then joined through welding and assembly if the part needs it.
We check it against the drawing. We measure it with rules, squares, calipers, and templates, then check the critical dimensions a second time.
You test it. If we've agreed you'll sign a sample, it comes to you to measure, fit, and sign before the run.
We run the batch to the signed revision. Each part is checked for its dimensions, material, finish, and revision letter before it leaves.
We keep the drawing on file. The approved drawing and its revision letter stay with us for the next order.
If a batch doesn't match the signed sample and the mistake was ours, we fix or remake it at no charge.
A first part you can measure by hand and test on your own machine suits a local fabricator well. A check that needs aerospace paperwork or lab equipment may not.
If your customer requires a formal AS9102 report, tell us when you ask for the quote. We'll say plainly what we can provide before you commit, so the paperwork never surprises you after the work is done.
Equipment stands, guards, and brackets are covered on our custom metal supports and enclosures page.
A first part goes faster when the check is planned before the cut. The metals and finishes we work in are listed on their own page.
For any custom job, What Duct Duct Goose Needs to Quote Custom Metalwork has the full list. More guides for repeat parts are in OEM, Prototype and Repeat Production.
A fully dimensioned drawing and a marked-up sketch are both a fine place to start. We'll tell you what's missing, and which dimensions we'll check hardest, before the first part is cut.
Standard ductwork and fittings price instantly on WebDuct, the online pricing and ordering portal, with a company account. Prototypes, production parts, stainless, and other custom work start with a request or a call.
At Duct Duct Goose, we specialize in sheet metal fabrication and stainless steel services for commercial and industrial applications, including HVAC systems, ducts, and custom metalwork. Please note that we do not offer services for automotive-related projects, such as vehicle parts, repairs, or modifications.
