u/United-Mortgage104

I would think that most of us have been in this situation before. You take a new job after gaining years (sometimes decades) of experience, working with newer tools and procedures, updated on newer technology, everything done with parametric modeling with ASME accurate drawing details. Now you're looking forward to brining your experience to this new (to you) company. You're excited and life is good.

When you get there and start looking into what they are doing, and why, you realize you're having more "WTF?!?" moments than you care to have. Working drawings are copies of pages that were made back in the 60s and 70s. Anything CAD related was done by someone with only a marginal amount of knowledge and ability with AutoCAD. The engineer before you was doing it this way since before dirt was invented. And the shop is just used to this and only says "that's how we've always done it" when you ask why.

How do you go about changing things to get them to be more modern, or at least following some kind of standard? How do you explain that their aging work force is eventually not going to be there, and a lot of the younger generation aren't going to know how to do it their way?

At some point in our careers, most of us have at least attempted to accurately model the threads of a bolt or nut. Creating the thread form profile, sweeping it along a helix, cutting it from a blank cylinder. It takes real understanding of thread geometry to pull it off cleanly, and there is genuine satisfaction when it works. That feeling is earned.

Do it right. Prove to yourself that you can do it. Then never do it again.

The only legitimate exception is if you work for an organization that manufactures threaded components, such as a fastener producer, a precision thread grinder, a tooling house, or a bottle cap manufacturer, where an accurate thread may actually be a deliverable. For everyone else, keep reading.

The problem with imported threaded features

I blame McMaster-Carr for this one, because they have made it too easy. With one click, you can download a threaded part with all the (mostly) accurate helical thread, just like the real part. The helix is there, the minor and major diameters are correct, it feels complete and professional.

However, it is also quietly destroying your assembly performance.

Threaded geometry is among the most computing-expensive topology you can introduce into a model. A single bolt with a full helical thread can carry tens of thousands of faces and edges. Multiply that by every bolt in your assembly and you have introduced more geometric complexity than the entire rest of the model combined. Rebuild times balloon. Drawing views render slowly or fail outright. Hidden lines produce visual noise that doesn’t benefit anyone.

None of that pain gets you any additional unit of manufacturing information, because a thread callout on a drawing already tells the machinist or assembler everything they need to know. All it does is make YOU feel good.

“But my workstation handles it just fine…”

Maybe it does. Maybe you have the most badass computer running a threadripper with 128GB of RAM and the model opens within seconds and you have never once had to wait on a rebuild. Good for you, genuinely.

Here’s the thing: engineering doesn’t happen in isolation. The moment you send that bloated model to a colleague, or vendor, or manufacturer, or client, it lands on whatever machine they happen to have. That might be a mid-tier laptop on a job site. It could be an older workstation at a small shop that doesn’t have the same budget as you do. It may be someone opening it in a web viewer that was never designed to handle a model with that much complexity.

I can promise that person is cursing your name. Not because they are underpowered, but because you made a decision that transferred your indifference onto their hardware. Your badass computer did not solve the problem. It just made the problem invisible to you.

Good CAD practice is not about what your machine can handle. It’s about what you are handing to someone else. Who has to touch it after you’re done?

What professional practice actually looks like

Every major CAD platform handles this the same way because the industry settled this question decades ago. Threaded fasteners are represented by simplified or cosmetic geometry: a smooth shank at the major diameter with an accurate head and drive geometry. The thread specification lives in the BOM, the drawing note, and the hole callout. That is not a shortcut. That is the correct method.

McMaster-Carr now provides simplified versions of most fasteners (STEP and Parasolid with the suffix “no threads”). SolidWorks Toolbox, Onshape’s Standard Content, and Autodesk Inventor’s Standard Parts library generally all work the same way. Use those versions. If a supplier gives you a fully threaded model, suppress or remove the thread features before you drop it into an assembly.

The same rule applies to your tapped holes

Modeling a tapped hole as a helical cut in a machined part is equally unnecessary. The correct approach is a cylindrical hole matching the appropriate tap drill diameter, or countersink or counterbore if required, and a standard thread callout on the drawing: thread standard, nominal size, pitch or TPI, class of fit, and depth. The machinist reads the callout and taps the hole. They do not need to see a modeled thread cut because it contains no information they cannot already derive from the callout.

The bottom line

A thread callout on a drawing is not a shortcut. Modeling an accurate helical thread masquerades as thoroughness while quietly making everyone’s life more difficult.

If your organization is using fully threaded fasteners and tapped holes in assembly and part files, you are paying for it with slow file opens, longer rebuild times, and the frustration of everyone that must use your files.

Threaded geometry belongs in the rendered product visuals for marketing or customer-facing documentation where cosmetic accuracy matters, and the performance tradeoff is acceptable. It does not belong in a working assembly. Know the difference.

TL;DR: Accurate, helical threads are most often not worth including in your models. Some exceptions are if you 3D print threaded parts, or if the threads are critical to the design. Modeling threads can expand your skillset, so it's worth learning, but be mindful of how your files will be used after you're done with them.