Using standardised screws is an easy way to streamline production for international projects. They can also save your manufacturing plant a lot of money and time, too. But, have you ever wondered what unified national extra fine threads (UNEF threads) or the United Thread Standard (UTS) is, and if they're actually considered "standard" anymore?
Some mechanical engineers tout the practicality of UNEF thread fasteners in machinery production, but if you've never used them, you might not know what they're used for. With the explosive popularity of ISO screws, you may even be surprised that UNEF fasteners are still used at all. So what makes UNEF threads standard, anyway?
Whether you're looking for the right fasteners for your next project, or you're just too embarrassed to ask your foreman what UNEF threads are, here's everything you need to know about how and why USEF threads are a standard.
What's the Unified Thread Standard?
Before we jump into UNEF threads, it helps to understand the history of the Unified Thread Standard, or UTS. If you're a metalworker in the United Kingdom, the United States, or Canada, you may have encountered the UTS without even realising it!
Before World War II, production companies found that each country had different screw measurements. This made maintaining international supply chains difficult, and factories were often forced to find screws that matched the destination countries' sizing before exporting goods. Often, even if the thread sizes for nuts and bolts were similar in other countries, the outer dimension and pitch of the thread caused different fasteners to fit incorrectly.
In 1949, the UK, US, and Canada created a standardised system for measuring threaded fasteners based on inch-based measurements. While the metric system of measurement ultimately proved to be more popular worldwide, the Imperial-based UTS system was one of the first attempts to offer international thread sizing standards.
While most global organisations have now switched to the more universal ISO screw thread, some manufacturers that create products for these countries still follow the recommendations of the UTS. In part, that's because these countries were resistant to adopt the metric-based ISO threads, so some current manufacturing processes still include UTS fasteners.
TS standards measure fasteners by the thread's nominal diameter, then the pitch measures as threads per inch (TPI), then the thread density, and finally the tolerance class. The pitch and thread density determine whether a fastener is considered coarse, fine, or extra-fine. If you're wondering whether UTS fasteners are the right fit for your project, a thread calculator can help you find the right fit.
What are UNEF (Unified National Extra Fine) Threads?
UNEF threads are an ultra-fine thread classification available in sizes larger than a quarter-inch. The extra-fine threads lock a fastener into place, making these fasteners ideal for machinery that vibrates heavily. While a courser threaded fastener could shake loose after prolonged vibration, the extra-fine threads hold even thin plates securely in place.
In most cases, a UNEF thread will be used to fasten machinery that isn't meant to be disassembled. That's part of why these sturdy fasteners are a popular option in the American machinery industry. When high tensile strength is needed, UNEF threaded fasteners are the way to go.
Jobs that require precision may call for UNEF threads, too. They offer better thread engagement on thin sheet metal, making them good for electrical jobs or machinery development. Some mechanics prefer to use UNEF threads for manual jobs, where they need a secure attachment that they can install on their own.
A finer thread comes in handy when tapping into hard materials like metals and hard plastics, when a typical self-tapping screw won't work. These precision fasteners remain standard in the industrial sector because of their large tensile stress area.
Often, UNEF threads are used in unique and specific situations where a fine-threaded fastener isn't ideal. The main difference between a UNF thread and a UNEF thread is that UNEF has more threads per inch. When the length of engagement is a concern, using UNEF threads over UNF might be your best bet for a strong hold.
Custom sized fasteners can be a headache to find, so it helps that the standard-sized UNEF threads are available in these situations. Using these fasteners can help meet custom design specifications while also being easy to find and buy in bulk. If you're looking to replace a fastener, a thread gauge can help you find the right size to order a new UNEF fastener.
Are UNEF Threads Right for Your Project?
Whether you're looking to replace existing fasteners or develop machinery made to last, UNEF screw thread and fasteners offer a secure hold you can depend on. While it may seem easier to go with a typical ISO fastener, these extra-fine threads can offer more staying power in standardised American measurements.
Metalworkers know how important it is to have the right tools for the job. UNEF threads are one option that you don't want to ignore. Whether you're working with thin metal sheets, hard plastics, or heavy machinery that can take a beating, UNEF threaded fasteners are the best fit for the job.
In some cases, custom thread sizes may seem like a better fit. However, you can often get the same impact of a custom threaded fastener with UNEF threads. Using UNEF threads is a much smarter option to ensure that replacement parts are available down the line.
There's a reason so many companies still use UNEF threaded fasteners. They get the job done.
Get the Right Tools for Any Job
The standard sizing makes finding UNEF threaded screws and fasteners easy. Even if you need a uniquely shaped dienut, a taper lead pipe, or a spiral point tap, we've got you covered. Here at Wiseman Threading Tools, we always have the exact tools you need in stock.
Looking for a specific UNEF product? Wondering whether UNEF threads are a good fit for your project? Contact us today to find the right tools for any job.
If you have any questions about any of our engineering tools, please call us on 01527 520 580