Inspection Stamps for Quality Control: Sizes, Inks, and How QC Teams Use Them

An inspection stamp is a small marking stamp, usually round, that a quality inspector presses onto a traveler, a tag, or the part itself. Read together with where it sits and the shop's stamp-control procedure, the mark shows that the item was checked, who checked it, and the recorded result. It is a quick, physical way to tie a decision to a person. Choose the stamp after you know where it will print, how much text has to fit, and which ink is rated for that surface.

A numbered stamp is only useful when the shop records who holds it and keeps inspection records legible for the full retention period.

What is an inspection stamp, and what does the mark tell you?

Picture the final-inspection bench in a machine shop. A batch of aluminum brackets has passed its dimensional checks, and the inspector presses "QC 07" into the final box on the traveler. Because the shop's procedure assigns number 07 to one inspector, anyone downstream, even an auditor two years later, can tell who inspected the work and that it passed final.

A quality control stamp typically carries some mix of these elements:

• Inspector ID. A number or initials assigned to one person, which is what makes the mark traceable.
• Status. ACCEPTED, REJECTED, HOLD, or a short code. Separate accept and reject stamps can reduce mix-ups.
• Stage or department. Receiving, in-process, final, or a code such as QA.
• Company initials, so a mark on supplier paperwork isn't confused with your own.

Round is the traditional shape, and a round mark is easy to tell apart from the dates and rectangular boxes already printed on many travelers. Our N32 round large inspection stamp is suited to QC and QA inspection routing and approval stamping.

What ISO 9001, FAA, and FDA rules ask for

The ISO clauses cited here require identification and traceability, the FAA regulation requires documented inspection status, and AC 21-43A recommends controlling inspection-marking devices. None of them prescribes a stamping product. Inspector-numbered stamps are one common way companies meet them under their own procedures.

ISO 9001:2015. Clause 8.5.2 requires control of the unique identification of outputs when traceability is a requirement, plus the records that make it possible. Clause 8.6 says release records must include evidence of conformity and traceability to the person who authorized the release (ISO 9001:2015 excerpts, Aviation Suppliers Association). Where a company's procedure uses inspector-numbered stamps, the number on the release record is what points to that person.

FAA production rules. Under 14 CFR 21.137, a production approval holder's quality system must include procedures for documenting the inspection and test status of products and articles, and for identifying and segregating nonconforming ones (eCFR, 14 CFR 21.137). The FAA's Advisory Circular 21-43A adds that procedures should ensure "inspection-marking devices are controlled and only issued to authorized persons" (FAA AC 21-43A).

FDA drug manufacturing. 21 CFR 211.80(d) requires each lot of components to be identified by status: quarantined, approved, or rejected (eCFR, 21 CFR 211.80). Batch records under 211.188 must identify the persons performing and checking each significant step (eCFR, 21 CFR 211.188).

One caution: a stamp shows who acted, but it is not automatically a signature. FDA's data integrity guidance notes that 21 CFR 211.186(a) calls for a "full signature, handwritten" on master production records, while accepting electronic signatures with proper controls (FDA, Data Integrity and Compliance With Drug CGMP). Follow the approved procedure; if it is unclear, ask Quality before adding a signature or stamp.

Receiving, in-process, and final inspection on the shop floor

Receiving inspection

A stamped receiving tag records that incoming material was checked. AC 21-43A asks production approval holders to keep articles awaiting inspection identified and separated from approved ones; a stamped tag shows which pile is which.

In-process inspection and the traveler

A traveler, or router, follows a job through the shop with a line for each operation. The inspector stamps each inspection point as it clears, showing how far a cart of parts has legitimately progressed. AC 21-43A says inspection status should stay identifiable through the whole manufacturing cycle, storage included, and lists production travelers among the records to retain.

Final inspection and release

Where the work instruction gives the inspector release authority, the final stamp documents that authorization. Some shops give final acceptance its own stamp or ink color.

Marking the part itself

Marking the part itself, where the drawing allows, calls for an ink built for non-porous surfaces. One limit: for scrapped aviation parts marked as not serviceable, AC 21-43A says ink stamping is not normally acceptable unless the ink is indelible and checked to confirm it can't be removed.

What size and shape should you choose?

Size follows the surface. A traveler block or tag usually fits 5/8" or 3/4"; a small part or crowded form may only take 1/4" to 7/16". At 1" and up there is room for company initials around the edge with a number in the center. The N06, N30 and N32 use oil-based Xstamper ink, while the F-series industrial models use an ink formulated for slick, hard-to-mark surfaces.

N325/8" roundF165/8" round, industrial

A border is optional on round models such as the F06 and N49. If you want final-release marks to look different from round in-process marks, the square N56 does that.

Text and layout for a QC stamp

A 5/8" circle holds a short ID plus a word or two; a 1/4" circle holds little more than a number or initials. Prioritize in this order:

• The inspector number, largest, in the center.
• A status or stage word around it, such as ACCEPTED, REJECTED, QC, or FINAL.
• Company initials, if parts or paperwork leave your building.

Keep fine text and thin fonts to a minimum at small diameters, because thin letters can close up when the stamp is inked and pressed. Our guide to ordering a custom stamp, including size, font, and layout, covers the preview step.

Color can carry meaning too: some shops reserve red for reject and hold. Xstamper Refill Ink is sold in red, black, blue, green, and several other colors, so a color scheme survives re-inking.

Which ink works on paper, metal, plastic, or oily parts?

Ink intended for paper may not adhere or dry properly on bare metal. Use an ink rated for the surface, check its drying time, and test on a scrap part first.

Paper, tags, and travelers

The N06, N30, and N32 carry oil-based Xstamper ink in a pre-inked die. We rate those three at approximately 50,000 impressions before re-inking and back them with a lifetime warranty, provided you re-ink with Xstamper Refill Ink only; other inks void it.

Metal, glass, and plastic

The F-series industrial stamps use a proprietary ink that is fast drying, permanent, and water resistant once fully cured. Average drying time for most colors is about 90 to 120 seconds, depending on atmospheric conditions; average drying time for white ink is 40 to 50 seconds. The die is laser-engraved silicone rubber, and the cap, sealed with an airtight o-ring, is designed to minimize ink drying out. We rate the ink excellent on aluminum, stainless steel, brass, ABS, and painted surfaces; good on glass, PVC, polypropylene, ceramic, and leather; and fair on polyethylene film and rubber. White and yellow inks need special care.

Refill F-series stamps with Industrial STSGA Refill Ink, made for the F06, F10, F11, F16, F20, and F30.

Oily, wet, or solvent-washed parts

None of those ratings describe a part with cutting fluid on it, and oily surfaces often need cleaning first. Remove the fluid and dry the area per your cleaning procedure, then test on scrap.

If your inspection marks go on cartons or other food packaging, use Hi-Seal 450. Its ink conforms to U.S. Department of Agriculture requirements for use on food packaging.

For applications involving solvents, Artline Hi-Seal 540 is highly resistant to most solvents and intended for parts and components. Test it against your exact solvent and wash process before relying on the mark. It is for use only with Hi-Seal pads and real rubber traditional stamps. Hi-Seal 480 glows yellow under UV (black) light. For damp surfaces or awkward spots, a marker often works better; see our guide to choosing a paint marker for metal.

How do you control inspection stamps and keep records audit-ready?

A stamp is only as trustworthy as the control around it. Adapt these controls to your staffing, approval roles, and record-retention procedure:

1. Assign one number to one person. Log the number, name, stamp model, and issue date in a stamp register.
2. Issue stamps only to authorized inspectors. This mirrors the AC 21-43A guidance on controlling inspection-marking devices.
3. Stamp at the time of inspection, never ahead of it. FDA's data integrity guidance expects records to be attributable, legible, contemporaneously recorded, original or a true copy, and accurate (ALCOA).
4. Add a date and signature where your procedure requires them. The stamp does not replace a required signature.
5. Collect stamps when people leave or change roles, and report lost ones right away. Consider retiring the number rather than reissuing it, so an old record never points to two people.
6. Check legibility. AC 21-43A says retained records should show legible data, acceptance stamps, and required signatures. Re-ink before impressions fade and let the stamp sit up to 24 hours, as we recommend.
7. Keep records for the full retention period. Under 14 CFR 21.137(k), FAA production approval holders keep quality records at least 5 years, and at least 10 years for critical components.

Frequently asked questions

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