Table of Contents
Watch the video: “Shop Tip: Threaded Inserts” by Tested
If you’ve ever stripped a hole or needed machine threads where a wood screw won’t do, threaded inserts are your best friend. In this Tested shop tip, Sean walks through the common types for wood, plastic (including 3D prints), and metal—plus where each one shines and what to watch out for.
What you’ll learn
- The essential insert options for wood, plastic, and metal
- How T-nuts compare to screw-in inserts in wood
- When to direct-thread into plastic vs. use press-fit or heat-set inserts
- How to repair stripped threads in metal (including Helicoils)
- Why rivet nuts are great for thin sheet metal
Understanding Threaded Inserts Threaded inserts create durable machine threads in materials that don’t hold them well on their own—like softwood, 3D printed parts, or thin sheet metal. The idea is simple: install an insert with internal machine threads, then use a bolt or screw that you can remove and reinstall repeatedly without destroying the base material.
Quick check
- Ask: Is the base material strong enough for direct threads? If not, choose an insert.
- Confirm: Will you need to disassemble frequently? Inserts help preserve threads over time.
From the comments Several viewers noted that inserts help when parts are frequently assembled and disassembled. Others added that for aluminum or softer metals, inserts can outlast direct threads under repeated use. While specifics vary, the video’s core guidance aligns: use inserts where direct threads are weak, risky, or already damaged. magnetic embroidery hoop
Wood Inserts: T-Nuts and Screw-In Types Hammering T-Nuts: Pros and Cons T-nuts are likely the first inserts you’ll find at a hardware store. Installation is straightforward: drill a hole for the threaded barrel, then drive the T-nut so its teeth bite into the wood. This gives you a machine-threaded hole.
Pros: They’re accessible and simple. Cons: They don’t always sit perfectly flush without counterboring, and under some conditions they can pull out or tear wood. Commenters shared a technique of recessing with a Forstner bit to help them sit flush and adding small screws between the legs to resist spin—tips that address common pain points.
Watch out
- Seat T-nuts carefully to avoid surface damage.
- Consider load direction: if forces tend to pull the T-nut out, evaluate an alternative insert or a design change.
Screw-In Inserts for Enhanced Durability Sean’s favorite for wood: screw-in inserts. Drill a hole per the insert’s packaging, then drive the insert using a hex key. The coarse exterior threads cut into the wood while leaving machine threads inside. These can sit more flush and resist spin if installed cleanly.
Pro tip Drive slowly and keep the insert perpendicular to the surface to avoid crooked starts. A driver with a hex bit can help maintain alignment.
Flanged Versions for Maximum Strength For added pull-out resistance, the flanged screw-in style can be installed from the back so the flange bears against the material—this distributes load more broadly and helps resist extraction. If your design allows access to the back side, it’s a simple way to add security.
From the comments There’s lively debate around T-nuts vs. screw-in inserts in wood. Some woodworkers prefer T-nuts for clamping strength and use a counterbore to seat them flush. Others like screw-in inserts but warn about alignment and pilot-hole sizing. The video’s advice is consistent: match the insert to load direction, accessibility, and the wood species. hoop master
Plastic Inserts: Press-Fit and Heat-Set Solutions Direct Threading in 3D Prints vs. Inserts Sean has successfully direct-threaded into many 3D printed parts by modeling or drilling the right diameter and using more perimeters (three to four) around holes. He’s cautious with acrylic, though—it’s brittle and easy to strip. For mission-critical joints or brittle plastics, inserts are more reliable.
Quick check
- Printing a functional prototype? Direct-thread can be fine.
- Need repeatable assembly or higher loads? Choose an insert.
Secure Press-Fit Inserts for Plastic Press-fit inserts have a slit on one end so they can collapse slightly during installation. You’ll size the hole to the insert and gently hammer them in; when you drive in a bolt later, the insert expands, and its knurls grip the hole walls firmly. This is a quick, dependable upgrade for many plastics and 3D prints.
Watch out
- First engagement can feel tight as the insert expands—this is expected.
- Avoid direct-threading in acrylic if strength matters; consider inserts instead.
Heat-Set Inserts with Soldering Iron: Tips and Tricks Heat-set inserts look similar but lack the slit and usually have a tapered end. Here, the soldering iron heats the insert, melting the plastic as you press it in. Let it cool so the plastic re-solidifies into the knurls—now you have a very secure metal thread in plastic.
Pro tip Special stepped soldering tips are designed for heat-set inserts and help avoid jamming. With a standard conical tip, the tool can wedge into the insert and pull it out during removal—exactly the headache Sean warns about.
Watch out
- Overheating can deform the part. Warm the insert enough to melt in smoothly, then stop and let it cool.
- Not all plastics are suitable—this method isn’t advised for acrylic in the video.
From the comments Viewers echoed the value of stepped tips and suggested simple hacks to reduce pull-out with regular iron tips. Others shared that modeling pockets for hex nuts and pausing prints is a viable alternative in some designs. The video’s core point remains: heat-set inserts offer strong, repeatable threads in many printed parts, and tool choice matters. dime magnetic hoop
Restoring Metal Threads: Helicoils and Other Options Why Inserts for Metal? Repairing Stripped Threads You won’t always cut new threads in the host metal. When threads are stripped and you need to keep the original screw size, use a thread-repair insert. One option shown is a solid insert with external threads and internal threads matching the original fastener; it often includes a pre-applied thread locker on the outside to keep it from turning.
Thread Repair Inserts with Threadlocker The process: drill the damaged hole larger, tap it for the external insert threads, then screw in the insert so its internal thread matches the original bolt. The red compound on the outside acts as a pressure-sensitive thread locker to prevent the insert from rotating in service. This is a compact fix when you need to keep the same bolt size in the reworked hole.
Helicoils: Compact and Strong (But Pricey Tools) Helicoils require a special tap and an installation tool that engages a tang to drive the coil into place. Advantages: they are small, restore original thread size, and are strong. Caveat: the kits and tools can be pricier than a basic insert. Sean notes that while the coils themselves aren’t expensive, proper tools are needed to install them.
From the comments Some pros favor solid inserts over coils in frequently serviced assemblies; others like coils for aluminum where repeated use is expected. The video is clear: Helicoils are robust and compact, but you’ll need the right tooling to use them. magnetic embroidery hoops
Rivet Nuts: The Solution for Thin Sheet Metal When to Use Rivet Nuts Sheet metal is too thin to tap effectively. Rivet nuts solve that by collapsing and “mushrooming” behind the sheet, locking a threaded sleeve in place. Sean used them to add leveling feet to sheet metal; they provided strong threads where traditional tapping wasn’t feasible.
Installation with Hand Tools vs. Pneumatic Options You drill a hole for the rivet nut, thread it onto the tool’s mandrel, place it in the hole, and squeeze or crank the tool to collapse the body. Pneumatic or hydraulic tools make quick work of this, while hand tools are cheaper but more effort—particularly for larger sizes. The result: a sturdy threaded anchor in thin stock.
Watch out
- With hand tools, large rivet nuts can be tough to set—take your time.
- Confirm the nut doesn’t spin after setting; if it does, the hole may be oversized or the collapse incomplete.
From the comments Multiple viewers pointed out affordable manual setters and even drill adapters that simplify installation. A few noted that in high-cycling applications, poorly set rivet nuts can spin—careful hole sizing and proper collapse are key. magnetic hoops for embroidery
Choosing the Right Insert for Your Project Matching Inserts to Material and Application
- Wood: T-nuts are common and strong when clamping from the opposite face; screw-in inserts offer flush installs and easy access. Flanged versions add pull-out resistance if you can reach the back.
- Plastic: Direct-threading can work in 3D prints when you add perimeters, but press-fit inserts and heat-set inserts give more durable results, especially for repeated assembly. Avoid direct threads in brittle acrylic.
- Metal: Use thread-repair inserts or Helicoils to restore original thread size in stripped holes; rivet nuts are ideal for thin sheet metal where tapping won’t hold.
Expanding Your Fabrication Arsenal Threaded inserts are versatile, compact solutions that prevent failures and extend the life of your projects. Whether you’re reinforcing a 3D-printed hinge, adding machine threads to a plywood jig, or rescuing a stripped aluminum housing, the right insert gives you reliable, reusable threads exactly where you need them. hoopmaster embroidery
From the comments: extra tips to try
- Square starts: Several viewers suggested guides or jigs to keep screw-in inserts perpendicular—especially useful in wood and plastic.
- Seat T-nuts flush: Counterbore with a Forstner bit; some add small screws between the legs to block rotation.
- Heat-set control: Use a stepped soldering tip; let the part cool fully before loading it.
- Rivet nuts: Confirm collapse and hole size to avoid future spinning.
Acrylic note Sean successfully cut threads in acrylic using a plastic tap, but he cautions it’s brittle and easy to strip. For higher confidence, use through-hole flanged inserts or plan on inserts rather than direct threads in acrylic.
Safety and care
- Heat-set inserts: Don’t overheat—excess heat can deform your part.
- Drilling and tapping: Keep bits and taps straight to avoid misalignment and damaged holes.
- Test fits: Especially in hardwoods and brittle plastics, test on scrap before committing.
If you landed here from a different search Sometimes folks researching shop fixtures and fasteners also shop around for unrelated tools. If that’s you, hello and welcome—this guide is strictly about inserts for wood, plastic, and metal. Feel free to bookmark and return after your other research on topics like hoop master station, mighty hoops, or even magnetic hoops if that’s on your list today. We’ll be right here when you need to add reliable threads to your next build. magnetic hoops for embroidery machines