Last updated June 2025
Engineers are under so much pressure to design properly functioning parts that they often fall into the trap of overengineering. The trouble is that overengineering inevitably increases cost and lead time on the machine shop floor.
At Focused on Machining, we have a simple philosophy about complex parts: “If you need a part machined a certain way, we’re happy to do it for you. But if your materials, features, or tolerances aren’t necessary for the function of the part, we can save you serious time and money.”
We always like to check in with customers during the quoting phase because a conversation gives us a far better understanding of a part than a drawing or model. During these conversations, we often identify cost and time-saving opportunities that can be achieved simply by making a part slightly less complex.
Today, we’re uncovering some of the common ways customers overengineer parts to help make you aware of these factors during the design phase.
7 Ways Customers Overengineer Parts
1. Making the tolerances too tight.
Tolerancing a feature to .002” or less indicates to our Colorado CNC machine shop that the feature is extremely critical. When a tolerance is that tight, we know that we need to really take our time, slow down our machining processes, and use fresh tools. But going slower and using higher-end tools in tight tolerance machining increases the cost and lead time of a part.
If you don’t want to pay more than what’s necessary, and your tolerances don’t have to be quite so tight, consider keeping tolerances at .005” or higher.
2. Adding complex features that have no functional value
It’s tempting to design a part that looks really cool. But keep in mind that complex aesthetic features like multifaceted surfaces are almost always challenging in precision machining. They may even require custom fixturing. Why spend more money than necessary for features that don’t improve part functionality?
3. Making walls too thin.
Since weight reduction is so important for aerospace applications, engineers will often design extremely thin walls to lightweight a part. This practice is especially common when designing the floor of a part.
But thin walls are more likely to warp, so any wall thickness measuring less than .06” creates risk in aerospace machining. And if you have exceptionally tight tolerances in addition to thin walls, the part will be even more challenging to make.
Unless you need extremely thin walls for the function of your part, we recommend keeping them over .06” so that they won’t easily bend or deform.
4. Choosing a finish your part doesn’t require.
Hard anodizing a part is risky because the process can cause dimensional changes significant enough to affect tolerances. If necessary, we’ll consider dimensional changes that can occur during this process before we begin machining. But if you don’t actually need hard anodizing, regular anodizing is much less likely to impact tolerances.
In some cases, anodizing may not be necessary at all. Many customers choose it by default to avoid leaving parts raw, but after a quick conversation, they often realize a chem film finish offers adequate protection with fewer tolerance concerns—and a lower cost.
If you’re not sure which metal finishing option is best for your part, we can help. Whether you’re considering anodizing, plating, or any other finish, we’ll guide you to the most functional and cost-effective solution.
5. Selecting materials that create more problems than they solve
Aerospace parts often wind up in such demanding environments that engineers may choose materials that are more high-powered than necessary. But just because a certain material theoretically exists doesn’t mean it’s easy to source.
If you’re concerned about thermal expansion because a part is going to Jupiter, you may understandably aim for a material with zero thermal expansion. However, if that material isn’t readily available (or available at all in some cases), there are alternatives. You can usually get comparable functionality from a material with very little thermal expansion that has been machined to the precise tolerances the part requires.
The challenges of material selection go far beyond aerospace applications. For example, we often see customers request UHMW because of the low price of the material. However, UHMW is so malleable that it can be difficult to hold even loose tolerances, often making machining a challenging and expensive process.
If you’re unsure which material is best for your part—whether you’re choosing between different aluminum grades, plastics, or exotic metals—we’re happy to talk through your application requirements.
6. Picking a harder material than necessary.
Stronger materials are inevitably more challenging to machine (they create more wear on the tooling). And yet, engineers will often pick a harder material than necessary, especially when it comes to stainless steel.
17-4 stainless steel, for example, comes in a series of different tempers based on the strength of the material. 17-4 stainless steel heat treated to condition H900 offers exceptional hardness. But 17-4 stainless steel heat treated to condition H1150 may provide sufficient strength for your application at a lower cost. Any opportunity to minimize heat treating will save you money.
7. Cramming too much data onto one page of a drawing.
This example is less about overengineering a part itself and more about how dimensions are presented.
As far as we’re concerned, there’s no such thing as too much information on a drawing. That said, some pages we receive are so packed full of dimensions that they’re actually difficult to decipher.
When dealing with complex parts in particular, it’s helpful to break your dimensions into 2-3 pages so that none of your important data gets lost in translation.
Bonus Tip: Match Your Hardware’s Precision to Your Part’s Precision
Here’s a situation we sometimes see: a customer sends us a part designed with extremely tight tolerances meant to house an off-the-shelf piece of hardware, such as a bearing. But when we check the hardware’s specifications, we find that it has a much looser tolerance.
In cases like these, we recommend matching precision with precision. Rather than over-machining a part to accommodate the hardware, it can be more effective to simply choose a higher-precision bearing.
Need Help? Let’s Discuss Your Next Part
At the end of the day, we’re always willing to provide custom CNC machining for exactly the parts our customers need. But we also like to help you save time and money whenever we can. Simplifying a complex part is often as easy as having a quick conversation, and it can have significant effects on the cost of production machining services for your project. So don’t be surprised if we reach out to discuss your quote!
Ready to work together? Request a quote from our Colorado machine shop and we’ll respond within 24 hours!