How We Inspect a Finished Blade: Dimensional Check, Hardness, and What the Record Contains

No batch of Steellogy blades leaves the production floor without a dimensional check against the drawing and a hardness measurement on a representative finished part. The inspection happens after heat treatment and final grinding — when the blade is in the form the customer will receive it — and the record stays with the batch. If a batch does not meet spec, it does not get packed. This post explains, in concrete terms, what we check, how we check it, and what ends up in the document that travels with the order.

Why output inspection is the inspection that matters

Inspection at intake catches the wrong steel. In-process inspection catches setup errors, heat-treatment distortion, grinding deviations, and other problems before final inspection. Output inspection catches everything else — the things you cannot foresee in either of the earlier checks, and the things that emerge from the interaction of heat treatment, grinding, and finishing. A batch that passed every check upstream can still come off final grind out of tolerance, or with a hardness that drifted because the heat-treat batch ran hot. Output inspection is the last chance to catch it.

It is also the only inspection that maps directly to what you receive. That is why it carries more weight, from a procurement perspective, than any of the upstream checks.

What gets measured: dimensional check

Every batch is checked against the drawing after final grind, with measurement focused on the dimensions that affect fit and cutting function. "Affect fit and cutting function" is doing real work in that sentence — we do not measure every dimension on every blade; we measure the dimensions that, if out of tolerance, would change how the blade behaves in the machine. Typically:

• Length, width, thickness (against drawing, to the specified tolerance).

• Bevel angle (primary, and secondary where applicable).

• Hole positions, slot positions, fixing geometry — anything that determines how the blade seats in the machine.

• Flatness (on long blades, where heat-treat distortion is a real risk).

• Edge straightness and parallelism (on slitting and shear blades).

Tolerances come from the drawing. If the drawing does not specify them, we apply the standard for the blade type and confirm with the buyer in the quoting stage — not at the inspection stage.

What gets measured: hardness

Hardness in HRC (Rockwell C) is measured on a representative finished part from each batch, at a position that does not affect the cutting edge or functional seating area. The reading goes on the inspection record with the measurement location, instrument used, inspector, and date.

Why this matters: hardness is one of the most informative measurable properties of a finished blade because it shows whether the heat-treatment target was reached. It tells you whether the steel got the right tempering cycle, and whether the finished part is within the hardness window selected for the required balance of wear resistance and toughness. A blade that is one or two HRC below the target window will wear faster than the drawing intended. A blade above it is brittle. Either is a problem, and either is caught by the measurement.

Where the drawing or order specifies a hardness target, the acceptance window is normally set around that target — often ±1 HRC, depending on steel grade, blade type, and application. The target itself is set during quoting, based on the application — not pulled from a default.

What gets measured: visual and surface

Less quantitative but not less important. The inspector looks at:

• Edge condition — no chips, no burr the customer would have to remove.

• Surface finish — consistent with the specification; where Ra is specified, the finish is checked against the agreed value.

• Coatings, if applied — visible coverage, edge condition, and no exposed substrate where the specification requires coating.

What ends up in the inspection record

The record is a single document per batch. It contains:

1. Batch number, drawing number, drawing revision.

2. Steel grade and heat number from intake (cross-referenced to the material certificate).

3. Dimensional measurements taken, with results against tolerance.

4. Hardness measurement(s) on the representative finished part, with target and tolerance.

5. Visual inspection notes.

6. Inspector signature and date.

The record stays in the production file and is shared with the customer on request, on a batch basis. We do not push it with every shipment by default, because most buyers do not want a stack of paperwork attached to a routine reorder — but it is there, and you can ask for it.

What happens when a part does not meet spec

Two paths:

• Reworkable. If the deviation can be corrected without moving the blade outside drawing tolerance or compromising its function — for example, a controlled regrind on an oversized dimension after heat-treatment distortion — the part goes back through the relevant step. The rework is logged in the batch file.

• Non-reworkable. The part is scrapped — not downgraded, not sold to someone else as a B-grade. "Doesn't meet spec" means the blade does not leave the floor as a Steellogy product. The cost of being wrong about this is much higher than the cost of scrap.

What this means for you, the buyer

Three things you can plan on:

• Every batch you receive has been measured against the drawing after final grind on the dimensions that determine fit and cutting function.

• You can request the inspection record for any batch, and the record will reference the steel grade and heat number from the original material certificate. Traceability is end-to-end.

• If a blade arrives out of spec, it is an exception, and the exception is something we want to know about so it can be traced — see What happens when you raise a complaint for what that path looks like.

On the broader point

Output inspection is not the most expensive thing a manufacturer does. It is one of the cheapest. The cost is the discipline of doing it on every batch, writing it down, and keeping the record where it can be retrieved a year later when a question comes in. That cost is fully embedded in how we work, because the cost of not doing it lands on the customer's production line, and that is not the relationship we want.

If you want a quote on a replacement cutting part, send the drawing and a sample of the part currently running in the machine — nothing less, nothing more.

Other posts in this series: inside our production floor, steel grades and where we use them, and what happens when you raise a complaint.