Most aerospace machine shops have extraordinary control over what happens inside their four walls. The moment parts leave for heat treat or plating, that control evaporates. Here’s why—and what it actually costs.
Here’s a scene that plays out in A&D machine shops every week: a batch of precision-machined aluminum housings—tolerances held to ±0.001″, surface finish dialed in, every dimension verified on the CMM—gets packed onto a pallet and shipped to an outside heat treater. The job ticket says 5-day turn. On day 7, somebody calls. On day 9, somebody calls again. On day 12, the parts come back warped, with discoloration that suggests the furnace profile drifted. The shop owner now has to choose between reworking, re-machining from raw stock, or having an extremely uncomfortable conversation with the customer about pushing the delivery date.
None of this had anything to do with the machining. The shop did everything right. But they’re the ones who eat the cost, manage the customer relationship, and absorb the schedule hit—because from the buyer’s perspective, they own the part until it’s delivered complete.
If you run a shop, you already know this story. You’ve lived some version of it. What’s worth examining is why this pattern is so persistent, what it actually costs when you add it up honestly, and why the usual fixes—finding a “better” processor, sending angry emails, switching vendors every 18 months—never seem to solve it.
This Is Structural, Not Anecdotal
It’s tempting to chalk finishing problems up to a bad vendor. Find a better heat treater, problem solved. But the pattern is too universal for that explanation to hold. The machine-to-finish handoff is fundamentally high-friction for reasons built into the industry’s structure.
There are roughly 13,000 machine shops in the United States. The vast majority have fewer than 20 employees and do under $2.5 million in annual revenue. These shops own CNC mills, lathes, grinders—that’s their core capital investment and their expertise. What they almost never own: heat treat furnaces, plating lines, NDT equipment, or coating systems. Those require entirely different certifications (Nadcap administers 26 separate accreditation categories), different chemistry, different capital, and different people.
(NAICS 332710)
typical shop
categories
So the division of labor is baked in: machining happens in-house, finishing gets outsourced. Almost always. This means every aerospace machine shop, regardless of size or sophistication, depends on outside processors for critical steps in their value chain—steps they can’t see, can’t control, and often can’t even get timely status updates on.
What It Actually Costs
Shop owners tend to think about outside processing problems in terms of individual incidents. A scrapped batch here, a late delivery there. But when you tally the full burden across a year—direct costs, indirect costs, and the stuff that never shows up on a P&L—the number is much larger than most people realize.
Research from the Institute of Industrial and Systems Engineers puts the cost of poor quality in manufacturing at around 15% of sales revenue on average, with a range from 5% to 35% depending on product complexity. Aerospace sits at the high end of that range. A Dassault Systèmes analysis found that cost of quality in the aerospace sector runs between 4.3% and 8.6% of total sales just in direct, tracked costs—the stuff that actually gets recorded in the system. The hidden costs push it much higher.
McKinsey’s 2024 aerospace supply chain report found that at one major US aerospace manufacturer, part nonconformance was the root cause of over 30% of all part shortages across programs. Not material availability. Not machining capacity. Parts that didn’t meet spec—many after outside processing.
For a small machine shop doing $2 million in annual revenue, even the conservative end of these estimates means $100,000 to $170,000 a year in quality-related costs. And a disproportionate share of that traces back to the finishing handoff, because it’s the one step in the process where the shop has the least control.
The costs you track
| Cost Category | What It Looks Like |
|---|---|
| Scrap & rework | Parts come back out of spec. You re-machine from raw stock, or try to salvage. Either way, you’re burning spindle time on work you already completed. |
| Expedited shipping | The processor blew the lead time by a week. Now you’re overnighting parts to the customer at your expense to avoid a late delivery penalty. |
| Customer corrective actions | Your buyer issues a CAR. You spend 10–20 hours on root cause analysis and documentation for a problem that originated at someone else’s facility. |
| Re-inspection | Parts return from outside processing and need full incoming inspection. Your quality team spends hours verifying what should have been done right the first time. |
The costs you don’t
| Cost Category | What It Looks Like |
|---|---|
| Owner time | The shop owner spending 5–10 hours a month chasing processors by phone, managing disputes, finding backup vendors. That’s time not spent on sales, operations, or strategy. |
| Lost follow-on work | A quality escape on a finishing step loses you a customer. They don’t tell you about the next three RFQs—they just stop calling. |
| Jobs you never bid | Buyer wanted a single-source quote for machining + finishing. You couldn’t offer it credibly, so you never even saw the RFQ. |
| Reputation erosion | In a regional supply base, word travels. One delivery miss, even if it was the heat treater’s fault, becomes “I heard they have quality issues.” |
Why the Usual Fixes Don’t Work
Every shop owner’s first instinct when a processor lets them down is to find a new one. And sometimes that helps—for a while. But the structural problems don’t go away just because you switched vendors.
The information asymmetry is permanent. Your heat treater knows their first-pass yield, their furnace utilization, their backlog. You don’t. You’re a customer—one of dozens or hundreds—and they have no incentive to share operational data with you. You find out about problems when parts come back wrong, not while they’re being processed.
You have almost no leverage. Most small machine shops represent a tiny fraction of their processor’s revenue. You’re not Boeing. You’re not Lockheed. If their furnace is full and your lot gets bumped a week, that’s your problem, not theirs. You can complain, but you don’t have the purchasing volume to demand SLAs, priority scheduling, or data transparency.
Certification narrows your options. In aerospace, you can’t just send parts to any heat treater. Depending on the program, you may need processors that are Nadcap-accredited, approved on a specific prime’s qualified supplier list, or certified to process particular alloys under particular specs. In some regions, that might leave you with two or three options. In others, one. Shopping around only works when there’s somewhere to shop.
The finger-pointing incentive is built in. When parts come back out of spec after heat treat, was it the thermal cycle? Or was the material already marginal coming off the CNC? With no shared data, no common inspection records, and no joint visibility into what happened at each step, both parties can make a plausible case. The dispute resolution process is essentially: argue, then somebody eats the cost. Usually the machine shop, because they’re the ones facing the end customer.
How It Works Today
- Find processors by word of mouth
- No shared quality data
- Status updates via phone tag
- Disputes resolved by arguing
- Processor’s yield is a black box
- You eat the cost of their failures
- Each shop negotiates alone
How It Could Work
- Pre-vetted, certified finishing network
- First-pass yield data shared with originator
- Real-time status on every lot
- Structured accountability with data trail
- Performance metrics visible to both sides
- Quality guarantees on routed work
- Network leverage on lead times and priority
What Vertical Integration Solves—and Why Most Shops Can’t Do It
There’s a proven solution to outside processing risk: own the processor. Vertically integrated aerospace suppliers that control machining and heat treat and surface finishing under one roof don’t have handoff problems. They have internal quality systems, shared data by default, and the ability to fix problems without a contract dispute. They can also quote full-service work as a single package, which is exactly what many buyers prefer.
This is why large integrators win work that small shops never even see. A procurement manager at a Tier 1 would rather issue one PO for a finished, inspected part than manage three separate suppliers and coordinate the routing themselves.
But vertical integration through acquisition requires serious capital—and it only works if you have the management depth to run multiple process types. A 15-person CNC shop buying a heat treat operation isn’t just buying a furnace. They’re buying Nadcap compliance obligations, pyrometry calibration programs, different safety protocols, and a business they don’t know how to operate. For the vast majority of small and mid-size shops, traditional vertical integration is simply out of reach.
That leaves a gap. Large integrators have the control and can offer turn-key. Small shops have the precision and the flexibility, but they’re structurally dependent on outside processors they can’t control and can’t see into. The ones in the middle get squeezed from both sides.
The Network Alternative
What if a machine shop could get most of the benefits of vertical integration—visibility, accountability, coordinated quality, full-service quoting—without having to buy a heat treat operation?
That’s the idea behind a coordinated finishing network: a curated group of finishing processors (heat treat, plating, coating, NDT) that commit to specific quality standards, share operational data with originating shops, and hold themselves accountable through measurable performance metrics.
This isn’t a directory. Directories already exist—Thomasnet has been around for decades. The difference is in what happens after you find the processor. In a directory model, you get a name and a phone number. In a network model, you get a quality-assured partner with visible performance data, lead time commitments, and a shared resolution process when things go wrong.
The key insight is that you don’t need common ownership to get coordination—you need shared data, mutual accountability, and aligned incentives. A network that provides those three things captures a large share of vertical integration’s benefits at a fraction of the cost and complexity.
What This Means for Shop Owners Right Now
Even before any network or platform exists to formalize this, there are things you can do today to reduce your exposure to the finishing black box:
Track your true cost of outside processing failures. Not just scrap—include the expediting, the owner hours, the re-inspection time, and especially the follow-on business you’ve lost. Most shops dramatically undercount this number because it’s spread across so many line items. Pull it together in one place and you’ll have a much clearer picture of the real cost.
Negotiate data sharing, not just pricing. When you evaluate a new finishing partner, ask about their first-pass yield on aerospace work. Ask whether they’ll share lot-level inspection results. Ask how they handle nonconformances. If they won’t share any data at all, that tells you something important about how they run their operation.
Build your own small network. Instead of using one heat treater and one plater, deliberately cultivate relationships with two or three for each process. Visit their facilities. Know their quality managers by name. Having a backup you’ve already vetted is worth far more than scrambling to find one during a crisis.
Quantify what full-service quoting would be worth. Go back through your last year of quotes and identify the ones where the buyer wanted a complete part—machining through finishing—and you either couldn’t quote it or quoted just your piece. How much revenue did those represent? That number is the upper bound of what a reliable finishing network is worth to your top line.
The Bigger Picture
The aerospace and defense supply chain generated roughly $952 billion in revenue in 2022, with nearly half flowing through the supply chain below the OEMs. That’s hundreds of billions of dollars moving through a network of small, specialized businesses connected by phone calls, emails, and handshake relationships.
Other fragmented industries—restaurants, home services, used cars, freight forwarding—have been transformed by platforms that brought coordination, data, and accountability to fragmented supply chains. Aerospace has been slower to change, partly because the compliance requirements are genuinely harder, and partly because the relationships are more entrenched.
But the finishing handoff problem isn’t going away on its own. It’s structural. It costs real money. And the shops that figure out how to solve it—whether through acquisition, through networks, or through some combination—will have a meaningful advantage over those that keep hoping their next heat treater will be different from the last one.