3D Printed Parts for an Aircraft Restoration - An Update

I think it's about time to update on my project 3d printing "faux gun barrels" for the restoration on a Bell P39 Airacobra non-flying display.

A restored P-39 Airacobra

The P-39 Airacobra I'm helping restore.

There's been some progress since my previous post!

The black PETG I was waiting for arrived, and I printed the new barrels using black instead of the gray I used for a test fit. 

One of the finished barrels

I found the PEtG I used worked well, but it was a little "stringy", and the finish wasn't quite as good as PLA or ABS. But it's nothing that a little sanding can't fix. It also helps that the barrels will be buried inside the flash suppressors, so a lot of them won't be seen. 

One of the guns temporarily placed in its the suppressor

What's left now is a final sanding to knock of the layer lines and a weathering to make the barrels look a little more weathered. 

Overall, it's been a pretty good first attempt!

 

3D Printed Parts for an Aircraft Restoration

Recently, I had an opportunity to mix some modern technology with the restoration of an 80 year old airplane.

The project is a Bell P-39 Airacobra, which is being restored to be a non-flying display at Planes of Fame Air Museum. One of the tasks I was given was to come up with four faux .030 caliber machine gun barrels for the wing mounts. 

An example of a restored P-39 Airacobra
By San Diego Air and Space Museum ArchivesUploaded by Bzuk at en.wikipedia - Source, Public Domain, https://commons.wikimedia.org/w/index.php?curid=24375991

The P-39 I'm helping with has a little ways to go before its finished!

All that was needed was a short length four to six inches so it looked like there was a barrel inside the flash suppressor. 

Given the tools I had available to me, I opted to 3D print the barrels. 

The first step was to get some measurements. Fortunately, Planes of Fame has an SNJ Texan that has a fake 30 caliber machine gun barrel I could use for measurements.

The SNJ and the barrel I could use for measurements.

With measurements sketched on a piece of paper,, I headed home andI created the model I needed in Autodesk Fusion. It wasn't a difficult model. I had it in about an hour or so. 

The 3D Model in Autodesk Fusion

The next step was to print it out. My plan was to print in black PETG, but it didn't arrive before the weekend, so I printed in gray PLA so I would have something to test fit. 

The PLA Print in Progress

Once Saturday rolled around, I had a chance to see how the test barrel fit. 

I was pleasantly surprised to see it fit well! It fit perfectly in one flash suppressor, and should go into the other three with a little light sanding. 

The 3D printed test part next to its "sample

The 3D printed part placed in its tube. 
Its not fully seated here.

The 3D printed barrel recessed in the tube. 
This will be its final position.

The next step? Print in the PETG I intended to, perform another test fit, and make preparations for permanent attachment.

In conclusion, it was a unique experience to be able to be able to use Fusion to create a model that could be 3D printed for the restoration. I'm grateful for the opportunity.  

But my part was indeed small, and I'm not the only one creating models that are turning into parts for this restoration. 

To see some amazing Inventor work that has turned into real parts for this restoration, check out Aviation CAD Technotes here! 

One last bit of "Legal Talk".

Any opinions expressed here are my own, and not necessarily those of Planes of Fame Air Museum. 

Barstool Philosophy - When Did I Become the Expert!

Every once in a while, I responsibly enjoy an "adult beverage" and ponder life. 

I call it "barstool philosophy".  

The beverage over which much
wistom is shared

Recently,  I celebrated my 51st time riding a giant rock around a "gianter" ball of fire floating in the vast expanse of space. 

Only a few days after that, I found myself helping seal the fabric envelope on a 1940s vintage  Taylorcraft. 

The Taylorcraft with fabric
over its steel tube frame

But this time "helping" meant handing the brush to someone half my age and saying, "you're up, kid".  

Somehow, when someone said, "he's the expert", and we looked around for that guy, I realized the eyes were looking at me. 

It didn't seem right. There's so much I don't know, so much I haven't done yet. 

I learned, or rather re-learned, teaching is a different mindset.

It's watching, guiding, stepping in, but not too much. It's saying, "if you do that, this bad thing will happen. Ask me how I know."

But we reached the finish-line in that milestone. The end product was pretty good 

The kids looked at me and said , "I hope we did good. "

Little do they know, the thought going through my mind was...

"I hope I did good."

So what lessons did I learn from this anecdote? \ "old guy with experience". I'm not sure when that happened. 

But happened it did. And I realized I had something to offer. While I don't know it all, the years had taught me more than I realized. Things that had become second nature by me were new, valuable lessons to those just starting out. 

Somewhere, without my realizing it happened, I became a mentor. 

I learned patience. I learned to look at a student and say, "You made this mistake. This is what you did wrong." And with a wry smile I'd say, with accurate self-deprecation, "Ask me how I know. I did it too.' 

And finally..

This post is pretty far removed from the Computer Aided Design Posts I've done in the past. My life and career has evolved. I'm not as deep in 3D modeling tools as I once was. The versions I use are old, and I don't use them at the level I did a few years go. 

But the lesson shares common ground.

For those of use who have a little more gray in our hair, and find ourselves squinting a little harder at our screens because "someone made the fonts smaller". 

Look to the fresh faced kids who were born after we graduated high school. 

You might have something to teach them. 

Lessons from a Mentor, a Quarter Century Later

 Sometimes, a lesson learned from long ago comes to pass. 

Recently I was working on a project that required I transfer the location of four threaded holes to a piece of aluminum so clearance holes could be drilled. The question was, how to do it? 

Sure I could measure out the holes, but the threaded holes were t-nuts pressed into plywood, and the holes for the t-nuts were measured using a tape measure. So the hole placement was made to more of a carpentry accuracy than an aerospace tolerance. But I still wanted to keep the clearance holes as tight as practical.

A 3D model of the T-nut that was pressed into Plywood

But I remembered watching an old tool maker when I was a young engineer fresh out of college. And if you haven't guessed by the title of this post, that was about 25 years ago.... Ouch. 

He showed me a "threaded hole transfer punch". It's a small tool that stores threaded screws that look almost like set screws. However they have points in them instead of the hex that one would expect from a set screw. 

I had my solution! I placed an order with McMaster Carr for the punch I needed, and I had it in my hands the next day. 

They're screwed into the holes you need to transfer. You then position the workpiece that requires the holes, give it a quick strike with a hammer. And now you have marks where you need to drill. 

Then it's off to the drill press to drill the holes you need. 

The transfer punch tool and two of its inserts.
The inserts are stored inside the tool. 
The tool also doubles as a wrench for the inserts.

The transfer punch with two punches threaded into the T-nuts

The marks left in the aluminum from the punches.
I'm afraid I didn't get a chance to get a picture of the drilled holes.

Using the tool that old die maker showed me, in the way he showed me how to use it, I had the holes I needed in no time flat. The whole process took about fifteen minutes. And that includes walking to another building where the drill press was kept! 

That's a lot quicker than trying to match the holes by measuring it out.  

And, in a strange case of deja vu, a young intern looked over my shoulder and asked me, "How did you mark those holes?"

So it was my turn to pass along the lesson I learned 25 years ago from an old die maker about the "threaded hole transfer punch". 

Other than sharing a cool story, what's the lesson? 

I would say to look for those small mentoring moments that can sometimes come from the most unexpected places. It might be from someone on the shop floor, an analyst in the corner of that dark office, or a program manager who's "been there and done that". 

A lesson can be learned in a few minutes can take years to pay off. But when it  does, it can be a life saver! 

Wow, that lesson was twenty five years ago.... Thinking of that I'm suddenly overcome by the urge to yell at some kids to get off my lawn....

About the Author:

Jonathan Landeros is a degreed Mechanical Engineer and certified Aircraft Maintenance Techncian. He designs in Autodesk Inventor at work, and Autodesk Fusion 360 for home projects. 

For fun he cycles, snowboards, and turns wrenches on aircraft. 

Why I chose to use Autodesk Fusion 360

Part of a Hydraulic Valve for 
a P-51 Mustang

Recently, I was asked why I used Autodesk Fusion 360 for my side project of modeling vintage aircraft parts. Why not use Autodesk Inventor? Or Dassault Solidworks?

Sitting down one evening, I decided to take a few moments to share my thoughts. These reasons are purely my own, as one guy cranking out models on evenings and weekends. I'm not an evangelist proclaiming my choice is better than yours. It's just that, my choice. 

Also, I do pay for a Fusion 360 subscription. I chose to take advantage of one of the promotions a few years back. I know this is likely still a hot button issue for some, but in my case, I'm glad I did. I thought it was

important that I mention that, in the interests of full disclosure.

 So, why did I chose Fusion 360? 

Accessibility

 A hydraulic housing in the
Fusion 360 mobile viewer

 The first reason I chose Fusion 360 it's easy for me to get. Yes. It's as simple as that.

Even if I chose not to subscribe, there's a free version that covers most of what I would choose to do. Sure, there's a cost associated with my subscription. But my cost for a yearly subscription is less than I'd spend on a weekend snowboarding. So for me, it's worth the expense to indulge my hobby.

Sure, there are probably ways I could get an educational copy of Inventor or Solidworks. Some are probably above board, others, more "gray market". 

At least in this case, I don't have to worry about stepping on anyone's

EULA (End User license Agreement). 

Capability

As far as bang for the buck. Fusion 360 does everything I need to do, plus more.

Most of what I do is currently limited to the parts, assemblies, and drawings. I haven't delved into the manufacturing or simulation space. But it's good to know I can do it should the time come!

I have used Fusion 360 to create *stl files for 3D printing and dxf files for a waterjet (see that post here), and overall, I've been happy with the results.

One thing I really like is the way Fusion 360 models threads. More than once I've been able to 3D print a usable thread out of Fusion 360.

A 3D print created with Fusion 360.
The fitting is threaded into 3D printed threads.

Ease of Administration

I've configured installations for Autodesk Inventor, Autodesk Vault, and to a lesser degree, Solidworks. All these tools are incredibly powerful. But with that, comes a great deal of setup and configuation. Where are the templates placed? How are you configuring your data management system? When you upgrade, what's your migration strategy? What are you using for a server?

For Fusion 360, the server is on the cloud, so there's no data to move when it's time to update hardware. 

When I purchased a new laptop, I installed Fusion 360 on my new computer, logged into my account, and had instant access to all my designs.

There was no need to migrate files or remap file locations. It was already there. In about an hour's time, I was up and running.

In Summary

In conclusion there isn't much, really. 

My big reasons why I chose Fusion 360. It works for me! Does that mean it would work for you on whatever projects you're working on? Maybe, maybe not! That's for you to decide. And whichever way you decided to go, happy 3D modeling!

Using Fusion 360 to Create Parts for a B-17 Restoration

A portion of the original print used to 
create the model.

 For many years, I've created models in Fusion 360. On occasion, I've 3D printed a few of my Fusion 360 models as "desk ornaments". 

But a few weeks ago, I had a fantastic opportunity to create a model that would be used to make a part for the restoration of a B-17 Flying Fortress. 

The part was a "friction washer" for use in the throttle quadrant. And the team needed geometry that could be cut on a water jet.

It started with a reproduction of the original Boeing print. Having the original dimensions made the modeling easy. It was interesting to note that even though standards have changed in the nearly 80 years since that print was created, it's not too different from the prints I work with today. 

The model of the friction washer, created in 
Fusion 360

Next, was to place the view on a drawing. The first goal was to dimension the drawing as a way of verifying all the dimensions were correct. Second, the drawing is what creates the 2D DXF file for the water jet. 

Once the drawing is created, delete any information that isn't required for the waterjet. This includes borders, title blocks, dimensions, centerlines and centermarks, etc. You might even consider creating a second page in the drawing for this purpose. 

Also, make sure to save the drawing before you export. I learned the hard way when I realized that the first file I exported still had all that extra geometry. Save the file before export!

The dxf geometry sent to the waterjet

Once I recovered from my snag. I sent the files off to my colleague for cutting. 

A few days later, we had our part and it fit perfectly, making for a very satisfying little journey. 

And while this little project was well worth a victory lap, there were three minor challenges that are worth mentioning. 

1) Drawing standards have changed over the decades, and while the drawing wasn't hard to interpret, some information wasn't where I'd expect it to be. Modern 3D modelers have spoiled us. We can "slap down" a new view in seconds. For the drafters of old? Adding the simplest view would take minutes. A more complicated one? Hours. 

The number of views was kept to a minimum. A part of single thickness, such as this one, will likely have the thickness dimension called out in a note. 

2) Not only have drawing standards changed, industry standards have changed. That material specification called out in 1943? It's been long superseded by a new standard. It's even possible that the standard that superseded the 1943 standard has, in turn, been superseded itself. 

Be prepared to spend a few minutes Googling the updated standards. Thank goodness for the internet! 

3) Finally, how does one interpret the tolerances called out on the drawing? Symmetric, +/-.005 for example, is easy. Model to the nominal. But what about a tolerance such as +.010/-.000? Do you "split the difference"? Do you aim for nominal? 

In my case, I decided to aim for the dimension as it was called out on the print. I figured that was the target dimension, after all. 

And in my case. It worked! Fusion 360 gave me an excellent dxf file that the waterjet used with no issuee, and the part fit perfectly into its intended position.  

It was a wonderful opportunity to contribute to a restoration. And a wonderful learning opportunity!

Acknowledgements

Print Reproduction via my Aircorps Library Subscription

Models and drawings created in Autodesk Fusion 360

A Milestone Creating a Fusion 360 Title Block!

I have completed the task I challenged myself with in my previous post. I finished up my reproduction of a 1940s era North American Aviation title block in Autodesk Fusion 360!

The original, and Fusion 360 Title block together

It was a little tedious at times, it's a lot of repetitive sketching geometry and inserting text and properties. 

But it's completed, and ready for use. I'm sure I'll find a few more things to adjust as I test it out. 

Ultimately, I was able to recreate nearly every feature of the title block. It's not an exact match. I couldn't find a solid fill to block out the box above the part number for example. But it is close, and it will serve it's purpose just fine. 

As more features get added to Fusion 360, I'll update the title block accordingly. 

The North American Aviation tile block finished

So now, it's time to start creating drawings! From there, I'll learn more lessons and make more adjustments!

Credits:

Title Block Sourced from my Aircorps Library subscription.

About the Author:

Jonathan Landeros is a degreed Mechanical Engineer and certified Aircraft Maintenance Techncian. He designs in Autodesk Inventor, Siemens NX, at work, and Autodesk Fusion 360 for home projects. 

For fun he cycles, snowboards, and turns wrenches on aircraft. 

A Trick - Creating Fusion 360 Title Blocks from an Image

 Happy 2022! Here's to hoping for a prosperous loop around the sun. 

One of my latest endeavors has been recreating 1940s aviation prints as 3D models in Fusion 360. The drawings are available via my Aircorps Library subscription, and they're a great look into how parts and assemblies were documented nearly 100 years ago. 

A piston for an actuator on a North American P-51 Mustang.
Model created in Autodesk Fusion 360

The models are the fun part for sure, but I also decided to recreate the drawings themselves too. 

The first part of recreating the drawing, is to recreate the title block of course. 

The title block image, ready for import into Fusion 360

\

It's still a work in progress, but I thought I'd spare a moment to document my progress.

It almost goes without saying, the process can be tedious. Since the original drawings are hand drawn, they have to be recreated from scratch. 

The thought of trying to "eyeball" the title block wasn't very appealing, but finally an idea dawned on me that made the process much less challenging. 

I imported an image of the title block, scaled it to a suitable size, and laid out the geometry on top of the image.

The title block in Fusion 360. The lines sketched in Fusion 360 are highlighted.

Overall, I felt pretty well. But there was one thing I did have to overcome

There's no image opacity setting like there are in other parts of Fusion 360. But I was able to see where my sketched lines were by highlighting them. I also extended the lines beyond the edges of the image. I can always trim them later. 

Finally, I'd also use the good old, "Delete, Inspect, Undo" trick by deleting the image, inspecting, and undoing the delete.

Overall, its working pretty well. I've found the process is much faster, accurate, and less frustrating than trying to scale by using the title block in a separate window. 

As I said earlier, it's a work in progress.  I'll share my final product when I'm done. Give me time, it might be a while! This is an "evening here and there" project! 

One Final Note

The team at Aircorps Library have done a spectacular job collecting, scanning, and sharing these vintage documents. Out of respect for their work, I won't be sharing any documents or models. Please, don't ask me to do so.

If you are really interested in their documentation, feel free to check out their site and investigate a subscription yourself! 

About the Author:

Jonathan Landeros is a degreed Mechanical Engineer and certified Aircraft Maintenance Techncian. He designs in Autodesk Inventor, Siemens NX, at work, and Autodesk Fusion 360 for home projects. 

For fun he cycles, snowboards, and turns wrenches on aircraft. 

A Musing on Modeling Safety Wire - How Much Detail is Necessary?

A question that was recently posed to me was; "How would you model safety wire in an assembly?" 

Safety wire on a fuel
divider on an 
aircraft engine

At first, I thought I'd write a post trying to summarize the standard, and how I've seen it approached in my travels over the years. But no matter how I tried to "summarize" the standard, it ended up too long, and so dry it put me to sleep.  So instead, I'm going to try writing this briefly, and hopefully to the point. 

First of all, Safety (aka lock-wire) is small diameter wire of various sizes that is used to prevent fasteners from loosening and ultimately falling out. It should always pull in a direction that tightens the fastener. It's usually twisted with 6-8 twists per inch. 

Of course there are more details, but they're covered by standards. In my aviation maintenance travels, that standard is AC43.13-1b, issued by the Federal Aviation Administration  (FAA). In my engineering travels, that standard is NASM33540.  I'm sure there are other standards.

That's important. The standards tell the installer how to secure the fasteners with safety wire.

So when it comes time to show safety wire on a model or drawing, is it normal to show the twisted wire?  Is it modeled exactly as shown in the

image to the right?

Heck no! That takes a lot of time and computer resources, which gets expensive fast. And having a standard to reference, there's little to be gained other than bragging rights for the designer. 

Instead, I've seen, and used, on of two alternatives. 

The first, is to use a sweep in the model, showing where the wire should go. This takes a little modeling time and dedication, but it will show up on the model, and propagate to the drawing when its created.

Safety wire shown in the model.
I've colored it in red here to make it stand out. 

The modeled sweep representing the safety wire on the drawing.
A leader references the standards in the notes.

The other, is to use sketch geometry when the drawing is created. It takes a bit of time to sketch in the drawing, but the results do a good job of showing the desired result.

Sketches on the drawing calling out the safety wire
Circles and lines represent the wire's twists.

Which ever method is used, a note can call out the standard to be complied with.  So the wire shown on on the drawing and model show where the wire should go, the note calls out the standard to reference.

If the installer has any doubts, the standard should be readily available for reference. I know in many cases, it's probably even legally required to be available. 

The next logical question for a reader may be, "How does this apply to me?" After all, while safe wire isn't uncommon, there are plenty of users who live long, fulfilling lives without ever touching safety wire.

If you get anything out of this post, ponder if there's anything that can be streamlined by adding more or less detail? How detailed does the model of that purchased part need to be? Are you spending extra time showing model details that are covered by a standards that can just be shown by a note with a leader? 

Perhaps take a few minutes to think it over. You might find you save hours! 

Acknowledgements

Models created by me in Autodesk Fusion 360

McMaster Carr models used:

• Round Head Screws (wire lockable) - P/N 90350A310 
• Flat Washer: P/N 92141A011
• 45 degree elbow (37 degree flare to NPT): P/N 50715K637
• 90 degree elbow (37 degree flare to NPT): P/N 50715K413

FAA Reference for Safetying: AC43.13-1b (See page 7-19)

NASM33540: This document is only available for purchase, so I've added a link to the old standard, MS33540.  It's very similar to NASM33540, as well as AC43-13-1b

Double Checking Your Work and Subverting Mr. Murphy

I once saw a graph that showed the cost of making a change in the CAD model vs  further down in the product design cycle

Spoiler alert! It gets more expensive as you move from design, to prototype, to production.  

One need only to cases like the Takata airbag recall, or Boeing 737 Max grounding or the impact of the impact of a a production level design change in in money, company reputation, and tragically, in lives lost. 

But I'm not here to write about such heavy topics. The example I'm choosing to document is a much lower stakes version of the same thing.  It's just a basic hobbyist example that at worst, is inconvenient and marginally embarrassing.

It's an access panel based on something you'd find on an aircraft. It's a concept for a potential future hobby project. I built one back when I was in school.

So I happily modeled away in Fusion 360, creating sheet metal parts and placing fasteners from McMaster Carr. 

After spending a couple of evenings of casual modeling, I was done! I took that moment we all love, I leaned back, looked at my work proudly, then prepared one last check before I took my little victory lap.

The completed inspection hangar, or so I thought...

And that's when I saw it. 

The countersunk rivets I had installed were the wrong ones. I'm not sure how I missed it initially, but obviously I did. 

So first, what's wrong with the rivet? 

It's a rivet with a 78 degree countersink, which means the countersink extends to the second sheet of metal being riveted.  This is a big no-no. When the countersink extends into the second piece of metal, the larger hole required in the first sheet of metal makes for a weaker joint.

The wrong rivet. I did match the countersink angle to match the rivet for clarification.

The incorrect rivet for this application. The countersink angle is too steep

The correct rivet is a 100 degree rivet. The shallower angle prevents the head from punching into the second sheet of metal. That means a stronger, and safer joint.

The 100 degree rivet, the correct one for this application. 
I know in the model the rivet does appear to just clip the second sheet.
But past experience has taught me that this combination does work.

The shallower angle of the 100 degre countersink makes a stronger joint

So that's the technical aspect of it, what's the other lesson?

I suppose the first lesson is make sure to check the hardware before you put it in. But we all make mistakes. That's where double checking comes in. 

A final check can help prevent the last little "oops" from slipping through. Even though we can't eliminate them all, we can reduce them with a little time. 

For those of us working in industry, a second set of eyes never hurts. In some places, multiple checks on a drawing are required. It's not a bad practice at all, one I think should be taken advantage of whenever possible. 

Some may argue it takes time, but it takes much less time than undoing a costly mistake. 

I've worked in maintenance shops where "second eyes" is a standard policy on items such as fuel system repairs. In other words, the person performing the work checks his work, and then a second technician or inspector checks it again. There often are even signatures required to prove that this step was performed. 

But that's it for today's anecdote. I re-learned a few lessons in a safe environment where the only bruise was to my pride. 

I hope you can take a few lessons from this musing, and keep making cool stuff! 

About the Author:

Jonathan Landeros is a degreed Mechanical Engineer and certified Aircraft Maintenance Techncian. He designs in Autodesk Inventor, Siemens NX, at work, and Autodesk Fusion 360 for home projects. 

For fun he cycles, snowboards, and turns wrenches on aircraft. 

Additional Resources: 

A nice  rundown on different types of rivets by- Hanson Rivet and Supply

A wealth of knowledge on general airframe repairs (start at page 4-31 for the Riveting Section) -Aviation Maintenance Technician Handbook 

Standard Parts Used on this Project.

.125 Diameter, 78 Degree Solid Rivet (The Wrong One) - McMaster Carr Part Number 97483A075

.125 Diameter, 100 Degree Solid Rivet (The Right One) - McMaster Carr Part Number 96685A170

10-32 Floating Nut Plate - McMaster Carr Part Number 90857A129

.094 Diameter Rivet (to Fasten Nut Plate) - McMaster Carr Part Number 96685A143

#10 Flat Washer - McMaster Carr Part Number 92141A011

10-32 Pan Head Phillips Screw - McMaster Carr Part Number 91772A826

Lessons from the Shop Floor - Helical Inserts do more than Repairs.

Many technicians, designers, and fabricators are familiar with helical inserts, often referred to by their trade name "Heli-Coil". 

A helical insert in an exhaust manifold

These inserts are made of a coil of diamond shaped wire. Looking like tightly wound spring, they can be installed in a special threaded hole to create standard metric and imperial threads.

In my early experience, I only saw them used to repair a damaged thread. As a matter of fact, they were used for thread repair so often, the name "Heli-Coil" became a verb. 

"Curses! This thread is completely boogered up! I'm going to have to Heli-Coil it! This why you always start a screw with your fingers!"

But as I gained more experience, I saw two additional uses for helical insert, and that's what I thought I'd share in this post. 

Wear Resistance

A 3D model of a free running (non-lockng) 
helical insert in an aluminum block

The first is to create a wear resistant hole in softer material, such as aluminum. Instead of waiting for the hole to get worn out, a helical insert is installed in the hole at the time of fabrication. The helical insert is made of a more wear resistant material such as stainless steel, although there are other materials available. This creates a more durable hole better suited if repeated installation and removal of the fastener is expected.

You might see this on a panel that needs to be removed periodically for inspection. Naturally, once the inspection is competed, the panel needs to be reinstalled. The more wear resistant helical insert lasts longer, and resists damage caused by cross threading. 

And if you have a really bad day and damage the insert, it's possible to remove the insert and install a new one without damaging the base material. 

Create a Locking Element

A 3D model of a locking helical insert.
Note the deformed thread in the middle.

Another element is to create a hole with a locking element in it. Locking helical inserts have a distorted thread in the middle that resists the screw backing out. By using a locking insert, the need for a screw with its own locking element, such as a nylon pellet, can be eliminated.

While this may seem like extra work for not much gain, this can be advantageous since you don't need to purchase fasteners with their own locking elements. Another advantage is in higher temperature applications where a nylon locking insert's performance may degrade to the point where it loses effectiveness.

And just like it's non-locking (also known as "free running") counterpart, it can be removed and replaced ,when it's locking element loses effectiveness.

 Wrapping it up

I've written this post based on helical inserts, but there are many styles of threaded inserts. Far more than I know about, let alone discuss in one post. So if the helical insert isn't your speed, there's likely another that will do the trick.  

For a sampling of just some of the different types of threaded inserts available for different applications and materials, take a look at the McMaster Carr catalog!

I hope you found this post helpful and informative. 

Let's get out there and design, fabricate, and maintain some stuff!

Appendix and Credits

• 3D models created in Autodesk Fusion 360.
• Threaded insert models downloaded from McMaster Carr
• Threaded insert models are based on the NASM/MS21208 standard for non-locking inserts, locking inserts are based on the NASM/MS21209 standard, although several standards, both imperial and metric, exist.

Finally! Looking for a video on how to install a helical insert? Check out this video here! 

Photo Credit: rustyheaps Repairing exhaust manifold, XK engine via photopin (license)