What a Lee Spring Quality Inspector Checks Before Your Order Ships

Quality Is a Measurement, Not a Certificate

Here's the blunt version: a spring supplier's certificate of compliance proves almost nothing. What matters is whether the part in your hand meets the print in your hand—consistently, across every batch. If 49,998 parts in a 50,000-piece order are perfect and two are off-spec, that's a quality failure. I don't sign it off. Simple.

A spring that meets spec 99% of the time still fails 500 parts per 50,000-unit order. That's not quality—that's a risk calculation.

I'm the quality and compliance manager at Lee Spring, a spring manufacturing company you probably know from our catalog. I review every outgoing order before it reaches customers—roughly 200 unique spring line items a year. In Q1 2024, I rejected 22% of first deliveries from our sub-suppliers. Every rejection traced back to the same root cause: the physical spring didn't match the documented specification, even when the certificate stapled to the box said it did.

That's worth understanding next time you're ordering compression springs, torsion springs, washers, or a garage door torsion spring replacement. Here's what I check, what fails, and what actually separates a good spring supplier from a box-mover.

The $22,000 Lesson That Changed My Inspection Process

I didn't always trust measurements over paperwork. The turning point was a batch failure in March 2023.

We received 8,000 internal tooth lock washers—part 880393 in our system—that looked correct at a glance. Clean surface, sharp teeth, decent packaging. Then I pulled a random sample and started measuring. The internal diameter was 0.012 inches under the printed spec. That's about the width of a human hair. On a lock washer meant to bite into a bolt head, the gap between fine and functional is exactly that narrow.

I'd assumed the supplier was making parts to our drawing. Didn't verify on the first batch. Turned out their tooling had worn, and a secondary operation shifted the final geometry just enough to matter. The vendor told us the parts were "within industry standard." That's the sentence I hear most in this job—and sometimes it's true. But if your application needs the spec on the print, industry standard is beside the point.

We rejected the batch. The vendor redid it at their cost. That quality issue cost us $22,000 in rework and delayed a customer's release by three weeks. After that, every spring contract we issue includes a sampling protocol and a dimensional measurement report from a calibrated gauge. It sounds like bureaucracy. It's actually insurance.

Here's the misconception I deal with daily: people assume expensive suppliers deliver better quality because they use better materials. But material grade is rarely the differentiator. Music wire from the same mill ends up in both premium and budget springs. The real variable is process control—how thoroughly the supplier checks tolerances, how they react to tool wear, how they handle a batch that fails. The causation runs the other way. Suppliers who deliver to spec consistently can charge more. The premium is based on process, not exotic alloys.

Five Things I Check on Nearly Every Spring Order

My daily routine isn't glamorous: calipers, an optical comparator, a spring tester, and patience. But the checklist matters more than the tool.

1. The print exists—and it's the right revision. Sounds obvious, yet it causes a massive share of discrepancies. A customer once referenced a torsion spring for a garage door opener, but the latest revision of their drawing specified the opposite wind direction. The spring did exactly what the drawing said. The drawing was wrong, and nobody caught it until installation.

2. Wire diameter and outer diameter stay within tolerance. On a compression spring, these two dimensions control the spring rate, stress, and free length. I see more failures from wire diameter variation than any other cause—especially when metric and inch measurements get mixed. Stainless wire per ASTM A313, music wire per ASTM A228—the standard tells you the material, but the tolerance tells you the quality.

3. Closed and ground ends are actually square. This is the most-copied but least-executed operation in spring making. You can have the right wire, right diameter, right length, and still get early failures if the closed end isn't square. If a spring sits crooked on a flat surface, that's a grinding issue. It fails springs faster than almost anything else.

4. Coatings pass thickness measurement, not just the "look" test. A zinc finish that looks right might be too thin to protect against corrosion. I measure coating weight, not color. A golden-yellow part and a pale-yellow part can look different and still have identical protection. The reverse is also true: the prettiest finish in the world won't save a part with wrong hardness underneath.

5. Packaging and labels match the parts inside. The dryest detail, and the one that causes the most customer frustration. The right spring in the wrong drawer is still the wrong spring. I've rejected entire lots because the label said 302 stainless and the parts were 304—both fine materials, neither matching the PO.

The Washers You Think Are Simple? Not So Fast.

Take a part like the no. 12 nylon standard flat washer. You'd think a nylon washer for a #12 screw is simplicity itself: round, with a hole in the middle. But a #12 washer has a specific outer diameter, a thickness range, and a hardness requirement. If the nylon is too soft, it deforms under load, and clamp force disappears. If the OD is oversized, it won't seat in a recessed bore. If the thickness is off, you're buying a spacer, not a washer.

These parts get rejected for dimensional variation more often than you'd expect—because nobody treats them like components that need tolerances. They're "just washers." Until one fails on an assembly line (and I've seen that happen; the line stops, the part gets blamed, and the actual root cause was a washer that measured 0.008 inches too thin).

Internal tooth lock washers like the 880393 have similar subtleties. Tooth angle, tooth count, material hardness, and internal diameter all matter. A lock washer without effective teeth is a flat ring. A lock washer with teeth that are too hard can fracture and shed debris into a motor. Both failures are silent, and both are expensive.

A Note on Garage Door Torsion Springs and Hinge Adjustment

Every month I get a call from a homeowner trying to "tighten" a garage door torsion spring. Here's what surprises people: those springs don't have an adjustment screw. Tension comes from winding the spring around a stationary cone, and the number of quarter-turns determines how much lifting force the door gets. Get the wire diameter or wind direction wrong, and the spring will fail—sometimes dramatically. On a garage door, that's a safety issue, not a convenience issue.

The same logic applies to door hinge springs. People search for "how to adjust a spring door hinge," expecting a screw they can turn. But in most cases, the tension in a self-closing hinge is set by the hinge manufacturer to match a specific door weight range. There is no adjustment—there's a replacement spring, and it needs to match the hinge manufacturer's spec, not the hardware store's suggestion.

One call stands out. A dental practice owner in Spring, Texas—Dr. Grace Lee—had a broken torsion spring on her clinic's back door and a door hinge that wouldn't close cleanly. We supplied the properly sized garage door torsion spring and an internal tooth lock washer set for the mounting bolts. But the hinge spring was a proprietary part, built into the commercial hinge. I told her what she needed to send the hinge manufacturer: model number, door weight, and hinge series. She was surprised that a spring could be that specific. That's the conversation I wish every buyer had before ordering—springs are engineered around a load and a service life, not a suggestion.

Whether you're choosing a compression spring, a torsion spring, a lock washer, or a nylon flat washer, the five parameters that matter most are free length, wire diameter, outer diameter, number of working coils, and wind direction. If you can't find those numbers, you're guessing.

Honest Boundary Conditions

Not every application needs the same level of fidelity. If you're building a prototype, testing a one-off idea, or making a fixture that sees light duty, a stock catalog spring is fine—and it should cost less than a custom part. The difference between a standard Lee Spring and a custom engineered spring is justified when the application is mission-critical or the load envelope is unusual.

Make that decision consciously. Know which parts are critical and which are just there. The most expensive spring you'll ever buy is the one that fails on your assembly line and shuts down a day of production. No catalog price can predict that cost.

Since 2022, I've pushed our team to treat every part number as a potential failure point, not a commodity. We've caught defects that would have cost customers real money, and we've rejected lots that would have shipped under a looser regime. It's not the most dramatic part of the job. But it's the part that keeps your line moving.