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TOLERANCE TRAP
Why smart engineers define fewer tolerances—and get better outcomes every time.
Issue 070
⚠️ Precision Pressure: Why You're Always Fighting Tolerances
In manufacturing, every thousandth of an inch matters—but not always the way we think it does.
We’ve all seen it: electrical terminals with ±0.001” tolerances on cosmetic edges. Busbars held to tighter-than-plastic flatness, even though they’ll be overmolded. These specs often come from old drawings or overcautious habits—not from function.
The result? Higher tool cost, longer debug cycles, slower validation. And usually, no real performance gain.
🛠️ Engineer the Hero: You Know the Product—Now Use Tolerances to Your Advantage
As a product or NPI engineer, sourcing lead, or tooling program manager, your job isn’t just to hit tolerances—it’s to hit the right ones.
But most teams are caught between “what might fail” and “what’s actually critical.” So, tolerances stack up, cost creeps in, and timelines slip.
You don’t need looser tolerances—you need smarter ones. That means asking: What actually matters here?
Stamping Reality Check: Align Specs with Process Capabilities
At Gromax, we’ve built progressive dies for everything from EV pressure sensor terminals to overmolded copper busbars. Whether it’s stainless, beryllium copper, or tin-plated brass, one principle holds up:
Not every feature needs to be critical.
Here’s a framework we use with customers during DfM reviews:
🔹 Critical-to-Function (CTF) Tolerances:
Tighten only what directly affects performance—like tab fit, spring contact geometry, or plastic alignment. These typically land in the ±0.0015–0.003” range for stamping, depending on material and feature location.
🔹 Reference or Supporting Features:
Use looser tolerances—±0.005” to ±0.010”—on blanks, ribs, or areas that don’t affect final assembly or electrical performance. Label non-essential dimensions as REF when appropriate to guide tooling focus.
🔹 Material Behavior & Allowance:
Stamped metals behave differently than machined parts. Account for grain direction, springback, and burrs. Don’t fight physics—design with it. Especially in overmolded parts, the plastic often dictates final precision more than the metal.
💡 Stamp Smarter, Not Tighter: What Happens When Tolerances Fit Reality
When teams focus on function-first tolerancing, big improvements follow:
Tooling debug is faster because fewer features require tight die tuning.
Quote-to-PO timelines shrink with less back-and-forth during review.
Supplier alignment improves—because expectations are matched to capabilities.
We’ve seen customers avoid weeks of tool iteration by simply flagging which features truly drive performance. It’s not about loosening standards—it’s about focusing them.
🎯 Your Two-Step Plan: Get Precision Where It Counts
Pull up your latest drawing—and circle only the dimensions tied to function.
Share it early with your stamping supplier for a manufacturability sanity check.
That 10-minute conversation could save weeks of frustration, especially as tolerance-driven costs and lead times continue to rise across 2025 projects.
Not sure if your tolerances make sense?
Share your drawing—we’ll help you separate the critical from the costly.
Gromax Precision Die & Mfg., Inc. specializes in designing and manufacturing precision metal stamped parts and tooling, including progressive stamping dies and custom equipment. With an on-time delivery rate of 99.68% and a defect rate of just 0.066%, the company ensures exceptional reliability and quality.
Gromax is ISO 9001:2015 certified and ITAR registered, serving industries such as medical, defense, aerospace, industrial automation, and automotive with high-quality, innovative solutions.