The Autolite Quality Checklist: 7 Steps for Inspecting Automotive Stamping Parts

Quick clarification: if you're here because you searched 'Autolite 26 spark plug cross reference' or 'Autolite 5924 spark plug,' this isn't that article. We're Autolite in the stamping world. We make metal parts for cars—brackets, housings, mounting plates—not spark plugs. But if your job is to accept stamped parts at an OEM or Tier 1 plant, this checklist is the one I use.

If a part doesn't fit, the CMM report is irrelevant.

This is not a replacement for a full PPAP (AIAG PPAP manual). It's a fast, repeatable incoming or pre-shipment audit. I've been reviewing stamped parts for about five years now, and this sequence catches problems before they become line stops.

Why This Checklist Exists

Ten years ago, many stamping plants treated visual inspection plus a dimensional report as 'good enough.' I don't think that holds anymore. What was best practice in 2020 may not be enough in 2025. The fundamentals—right revision, right datum, no burr, no crack—haven't changed. But the tools and the level of validation expected by automotive customers have changed. If your inspection plan still looks like the one you used in 2019, it's probably time to update it.

The 7-Step Checklist

Step 1: Verify the revision, not just the part number

Start with the drawing. The part number can be correct while the revision letter is wrong, and a wrong revision can mean wrong hole locations. In Q1 2024, I rejected 8,000 mounting brackets because the vendor shipped the previous revision—same part number, different hole pattern. That cost roughly $22,000 to redo and delayed our launch. All because nobody checked the revision field.

Make it a habit: compare the drawing revision on the router, the part print, and the supplier's packing slip. If they don't match, stop the receiving process before you measure anything.

Step 2: Confirm the measurement setup before you trust the numbers

Don't accept a CMM report just because it says 'all dimensions in tolerance.' Ask how the part was aligned. If the supplier used the wrong datum structure, the report can be mathematically perfect and practically useless. The most frustrating part of this job is watching a clean-dimensional report sit next to a part that doesn't fit. You'd think the report would be enough. It isn't.

If you don't have a CMM of your own, at least check the critical dimensions manually with a micrometer, caliper, or pin gauge. Focus on the characteristics marked as 'critical' or 'SC' on the drawing.

Step 3: Feel the surface finish on functional faces

Surface finish is not cosmetic. On stamped parts, a rough face can mean a leak path, higher friction, or poor welding. Run your fingernail across the surface; if it catches, that's a red flag. If you need numbers, use a profilometer. If you don't have one, use a surface roughness comparator. For a sealing face on a fuel pump housing, I'd reject any finish that looks torn or has galling.

Step 4: Run an eddy-current crack check (the step most teams skip)

This is the one I see left out of most inspection plans. A stamped part can pass every dimension and still have a microcrack along a bend radius. You won't see it until it's too late—or until it becomes a warranty failure.

Eddy-current testing is the practical fix. The physics is based on Maxwell's equations in differential form, specifically Faraday's law: a changing magnetic field creates eddy currents in the metal, and a crack interrupts the current flow. You don't need to derive Maxwell's equations to use a hand-held eddy-current probe, but you do need to understand that the signal is telling you something real.

I have mixed feelings about portable eddy-current equipment. On one hand, it's an extra investment. On the other, it caught cracks that standard dimensional inspection would have missed. In one comparison, same supplier, same part, same volume, we ran one quarter with visual-only inspection and the next quarter with eddy-current screening added. We caught roughly three times more cracked flanges. That was enough to change my mind permanently.

If you use coated parts, run this check before plating or coating. The coating hides the crack. Your IATF 16949 auditor may not ask for eddy-current on every stamping, but they will ask how you control crack risk. 'Visual only' is not a strong answer.

Step 5: Check burr height and edge break

Burrs are not just a sharp edge issue. On a stamped part that goes into a 60 psi fuel pump, a loose burr can break off, get carried by the fuel, and score a bore or damage a seal. Check the drawing for the maximum burr height or edge break requirement. If the print doesn't state it, use your internal standard and document it.

A simple burr gauge or a 10x loupe is enough for most jobs. The rule I use: if the burr can be lifted with a fingernail, it's too big.

Step 6: Verify cleanliness and packaging

Contamination can make a good part bad. Look for residual drawing oil, loose metal chips, rust, and water stains. I've seen parts rejected because the packaging trapped moisture and corrosion started before the part hit the assembly line.

You didn't land here because you searched 'how to clean air purifier filter'—but the logic still applies. An air purifier stops working well when the filter is dirty. A stamped part stops working well when oil, chips, and moisture get on the surface. Cleanliness is not cosmetic; it's a performance factor.

Step 7: Do a physical fit test

Finally, fit the part into the real assembly. Not a fixture, not a test stand—the actual mating part or a duplicate of it. Tolerance stack-ups can pass individual dimensions and still fail at final assembly.

This is the same thinking as a spark plug check: an Autolite 5924 spark plug has to seat properly, seal, and reach the correct depth in the cylinder head. A stamped component has the same requirement in its own assembly. If the part doesn't fit, reject it. No amount of paperwork changes that.

Final Notes

Don't copy this checklist into your QMS and call it done. Use the special characteristics list on your drawing to set sample sizes and frequencies. Some parts need 100% eddy-current screening; others might only need a random sample.

And remember: the old standards aren't wrong. The reason to inspect hasn't changed in decades. What has changed is the execution—portable probes, digital CMM reports, and customers who expect fewer surprises. It took me about 120 supplier visits to learn that the best inspection plan is the one that makes you look at the actual part, not just at the paperwork. This checklist is how we do that now.