When to Use Threaded Inserts in CNC Machined Prototypes

Does your prototype model really need threaded inserts? 

There are plenty of good reasons to incorporate threaded inserts like Heli-Coils into your prototype design. They’re great for reinforcing screw threads and transferring forces on soft materials. 

But for many applications, standard drilling and tapping can be a more functional and cost-effective solution for CNC machined prototypes. 

Wondering if your prototype model could benefit from threaded inserts? Read on to learn more. 

Downsides to Using Threaded Inserts

Typically made out of stainless steel wire, Heli-Coils are threaded inserts with diamond-shaped cross-sections that screw into receiving threads.

The coils remain compressed during installation, then expand against the housing. The resulting tension keeps them in place.

While Heli-Coils provide a sturdy reinforcement for soft materials, they’re not always the best option for all materials or budgets. Downsides of using threaded inserts include: 

• Higher cost than standard drilling and tapping. The price of threaded inserts combined with added installation charges can add up quickly for prototype models. These costs are even more prohibitive at production volumes, where it’s possible to save tens of thousands of dollars with an alternate solution like Loctite.

• Insufficient strength. Though their depth is short and inherently weak, Heli-Coils are often made of strong materials, like stainless steel. They work well with aluminum, plastic, and other softer materials. But they’re not strong enough to effectively fasten stainless steel parts unless they have a special coating.

• Long installation time. Each Heli-Coil takes about 30 seconds to install. That may not seem like much time during the prototype phase, but it makes a big difference in lead times in production manufacturing. 

When to Use Threaded Inserts

Before deciding on threaded inserts, consider the intended function of these fasteners. Will they be used for frequent assembly and disassembly? If so, Heli-Coils are probably a wise choice. 

Threaded inserts are best suited for locations where assembly and disassembly occur most often. They’re ideal for applications that require fastening a part to a fixture plate and testing it hundreds of thousands of times.

If, however, your priority is thread strength, threaded inserts may not be the best option. Sometimes adding Loctite to the screw portion provides enough strength without the extra cost and time of installing threaded inserts.

Still have questions about threaded inserts for your CNC machined prototype? We’re here to help. Contact us today to discuss your prototype model.