At KT Tech, we do everything we can to ensure the success of your project. These efforts go well beyond just our CNC precision machining services. Our long-term customers keep coming back to us because they know we’re a true partner at every phase of the manufacturing process.
For instance, if we identify any issues in the design at the start of a project, we’ll always bring them to your attention and offer solutions. Unlike many other shops that simply follow the design as provided—ignoring potential red flags—we take a proactive approach. By addressing these issues early on, we help you avoid costly delays and the need to remake parts due to design flaws.
As experts in manufacturing, we emphasize the importance of Design for Manufacturing (DfM). We work closely with our customers to ensure that every part is produced efficiently and cost-effectively.
This is our second in a series on DfM recommendations. We’ll share our top suggestions for optimizing thread design to enhance the quality and performance of your products.
Common Issue 1: No Chamfers On Difficult Male Threads
The image above highlights one problematic thread design we often encounter. This thread looks simple enough in CAD form, but in reality, it’s surprisingly difficult to manufacture.
The end of this thread at the bottom is the first challenge. It is extremely difficult for a tool to successfully reach into the space to create the bottom threads. We can, theoretically, devise ways to do it, but those methods are typically impractical and become expensive quickly.
This isn’t the only issue with this design. When we machine threads like this, generally, the start of the thread is not usable either. The start of the thread, in practice, does not have a clean shape like in the CAD image displays. Instead, the beginning of the thread becomes so thin, leading to deforming and bending.
DfM Solution 1: Suggestions for a New Thread Design
Better, But Still Not Ideal
To make this more machinable and cost-effective, the design could add chamfers at the beginning and end of the thread. You can see in the image above that this creates a relief at the bottom – that relief should be one pitch length at minimum. But if the rest of the design is maintained as it was, that means one pitch length from each end is now unusable. This creates new issues, because now the only usable thread in this design is the single turn in the middle. That turn alone will not be strong enough and will be easily damaged. So adding chamfers isn’t enough, and the design has to be changed in other ways as well.
The Ideal Thread Design
This image depicts the ideal solution: to use finer pitch thread to have at least 3 useful turns and three pitch lengths in addition to the chamfers. More than 3 turns can be better in some cases – it’s sometimes useful to have up to 7 turns. But in the end, this design will not only be strong and functional, but it will be significantly more cost-effective and machineable than the original design.
Thread DfM Issue 2: Deep internal threads
Another issue we often see is deep internal female threads (the threads are represented by the blue highlight in the image below). If a part definitely needs this feature, it can be made using a special process, but it’s very difficult and will increase the price of a part.
In our experience, when we discuss the issue with engineers, they say that any additional threads beyond seven turns is not adding meaningful performance. So five turns is typically sufficient for these internal threads. Adding more turns beyond seven doesn’t make it functionally stronger, but it does increase price by making it more difficult to manufacture. So the solution is fairly simple: reduce the number of threads and the depth of the hole.
Thread DfM Issue 3: Blind Tapped Hole Depth
One final note, too, is that any blind tapped hole needs to be deeper than the thread depth. Customers sometimes will have very shallow blind tapped holes, and this adds difficulty to manufacturing the part because it does not leave sufficient room for tool clearance or chip accumulation. So it’s important to make the blind tapped hole deeper than the thread depth.
Talk to Us Today
These are just a few of the most common issues we see with thread designs. But with our years of experience in areas like Swiss machining services, prototype machining services, and beyond, we flag a lot of potential issues and discuss them with customers to make sure their parts are made as cost-effectively as possible.
Talk to us today about your next project. We’ll be sure that it’s optimized for manufacturability and success.
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