Approved Machining

CAD will let you draw a wall so thin you could read a newspaper through it. CAD will not warn you that this wall will become a very expensive piece of confetti the moment a cutter touches it.

That's the thing about wall thickness—it's a simple design decision in CAD that becomes a physics problem on the machine. Thin walls flex under cutting forces, chatter against the tool, and drift out of tolerance in ways that don't show up until you're on a finishing pass with an almost-done part. And then they do show up. Loudly.

Going too thick isn't great either. You're just paying to remove material that didn't need to be there, which means longer cycle times and higher costs for a wall that's stronger than it needed to be.

We break down how to find the sweet spot on the blog.

Read more: https://www.approvedmachining.com/blog/thin-wall-thickness-limits-for-cnc-machined-parts



Related: Precision Machined Products Association - PMPA

Every assembly split across multiple shops eventually produces the same email: "our part is in spec, the problem must be on their end."

Spoiler: everyone's part is in spec. The problem is that three shops machined three components to three slightly different interpretations and nobody talked to each other along the way. The tolerances were fine individually. Together, they're a mess.

When one shop machines every component and assembles the final product, that email is never necessary. At Approved Machining, we own the full picture, so you don't have to referee.

Tired of being the middleman? Here's how a one-shop approach actually works: https://www.approvedmachining.com/blog/cnc-machined-assemblies

Steel and stainless steel are like siblings. Same last name. Different personalities. One's the workhorse who shows up cheap and reliable. The other costs more but handles things the first one can't. (You know which one you are.)

➡️ Steel is the go-to for a reason. It's strong, it machines well, it comes in a ton of alloy options, and it won't blow up your budget. Alloys like 1018 and A36 cover your general-purpose needs, while 4140 and 4340 step in when you need real strength and hardness. The catch is that it doesn't hold up well against moisture or chemicals on its own, so it usually needs a coating or surface treatment to survive in harsher environments.

➡️ Stainless steel earns its premium when the environment gets ugly. It thrives in conditions that would wreck standard steel, from moisture and heat to chemical exposure. 304 and 316 lead the way on corrosion resistance, 303 machines more easily when that's a priority, and 17-4 PH adds high strength to the equation when the application calls for both. It's harder on tooling and more expensive across the board, but when the application demands it, nothing else will do.

The right choice always comes down to where the part ends up and what it has to survive when it gets there. Not sure which way to go? We'll help you sort it out.

Here are some of the materials we work with most often: https://www.approvedmachining.com/cnc-machining-materials



Related: ASM International

A ballpoint pen tip is a tiny metal ball rotating in a socket with tolerances tight enough that ink flows out smoothly instead of blobbing all over your hand.

And you just chew on it.

Happy National Ballpoint Pen Day. There's genuine precision engineering happening inside something most people lose three times a week without blinking. That ball has to rotate freely, seal when it's not in use, and deliver consistent ink flow across thousands of strokes.

When it works, nobody notices. When it doesn't, you're shaking it over a napkin at a restaurant like that's going to fix a tolerance issue.

One of the reasons your favorite pen works so well is because someone got the tolerances right on a part you'll never see. At Approved Machining, we make those kinds of parts.

Request a quote: https://www.approvedmachining.com/request-for-quote

There’s a hidden tax on a lot of machined parts.

It’s called “±0.001 everywhere.”

Tight tolerances absolutely have their place:

→ Bearing fits
→ Sealing surfaces
→ Precision bores
→ Alignment-critical hole patterns

But on non-functional features, cosmetic faces, or clearance holes, that extra precision may not improve the part. It may only make it slower, harder, and more expensive to produce.

Our latest blog looks at when tight tolerances are worth it, when they aren’t, and how to avoid paying for precision your part doesn’t actually need.

Check it out here: https://www.approvedmachining.com/blog/how-to-specify-machining-tolerances



Related: Precision Machined Products Association - PMPA

How to Specify Tolerances Without Over-Engineering The same part can cost $40 or $400 depending on how tolerances are applied. See how to specify smartly and avoid over-engineering.

Some parts are functional.

Some parts are beautiful.

This one had the audacity to be both.

Machined from copper with tight features, clean pockets, and every dimension exactly where it should be.

Request a quote: https://www.approvedmachining.com/request-for-quote

Some machine shops make the same bracket 10,000 times. We machine parts for industries where the parts are complex, the tolerances are tight, and nobody's ordering 50,000 of the same thing.

Prototypes and low-volume production are our bread and butter, which means no two weeks look the same around here. Here’s where we spend much of our time:

➡️ Robotics: a robot arm that's off by a few thousandths doesn't pick up the part. It picks up the table.
➡️ Medical: "close enough" is not a phrase anyone wants to hear in an operating room
➡️ Instrumentation: the tool that measures everything else doesn't get to be the one that's wrong

We’ll let you decide if our job is cooler (It is.).

Learn more about the industries we serve: https://www.approvedmachining.com/industries-we-serve



Related: Association for Advancing Automation

We get it…shiny is satisfying. So is bubble wrap and those videos of people pressure washing driveways. But that doesn't mean your non-functional internal pocket needs a mirror finish.

A smoother surface finish doesn't always mean a better part, but it almost always means a more expensive one. A single Ra callout can add tool passes, slow feed rates, and trigger secondary operations that do nothing for how the part actually performs. And we see it all the time on surfaces that'll never be seen, touched, or mated to anything.

Before you submit that next drawing, it's worth asking what each surface actually needs to do. The answer might save you more than you'd expect.

We break down when surface finish actually matters (and when it doesn’t): ​​https://www.approvedmachining.com/blog/how-to-choose-the-right-surface-finish-for-cnc-machined-parts



Related: ASME (American Society of Mechanical Engineers)

Your part doesn’t need to be on a submarine to qualify for harsh environment design.

🌦️ A rooftop unit baking in the summer and freezing in the winter? Harsh.
🔧 A factory floor with constant vibration and chemical exposure? Harsh.
🌊 Anything within smelling distance of saltwater? Also harsh.

Most premature part failures trace back to one thing: the environment wasn’t part of the design conversation.

Here’s how to design parts that actually hold up in the real world: https://www.approvedmachining.com/blog/designing-cnc-parts-for-harsh-environments

Most materials come off the machine looking like they need a shower. Brass comes off looking like it just got back from one.

It machines clean and somehow makes even simple geometry look more expensive than it is.

We don’t get to work with it every day, but it’s always a good day when we do.

Got a project? Let’s talk: https://www.approvedmachining.com/request-for-quote