Precision machining has come a long way since we opened our shop more than 20 years ago. But even the most advanced technology has limitations. You may be surprised to learn that certain easy-to-design features are actually impossible to machine!

Yet several times a month, our precision machine shop receives part drawings with features that simply cannot be achieved through straightforward CNC machining.

Here’s a look at the three most common non-machinable features. Eliminate these elements from your future designs and enjoy faster quotes and lower-cost manufacturing! 

1. Square Inside Corners

At least three times a week, we have to flag a design that calls for square interior corners.

Square bosses (protruding features) are doable. But square inner corners are impossible to machine because the tool’s radius is always larger than the corner radius. Even if we were to customize a tool to precisely match the requested corner radius, the shape and movement of the tool would invariably soften the corner’s sharpness.

In some cases, we can achieve square inside corners with EDM or broaching (pictured), so talk to our team if you’d like to investigate other possibilities. 

To adhere to Design for Manufacturing (DFM) best practices, however, we recommend designing your inside corner radii to accommodate your bolt, insert, or application; don’t design perfectly square inside corners for their own sake.

2. Features Requiring Extended-Length Tooling

When projects require extended-length tooling (tooling longer than 2”), customers can expect higher costs and longer lead times. It can also be difficult to achieve precision tolerances with extended-length tooling. Allow us to explain.

This 10” long door assembly was designed with a hole extending through the entire length of the part. To achieve this feature, we had to order a 5” long tool and drill half of the hole from one side of the part, then complete the hole from the other side.

Obtaining longer tooling added a week to our customer’s lead time and increased their project’s cost. We also had to run our machine more carefully and slowly to prevent the chatter that longer tooling can cause and hold the specified tolerances. Thankfully, this tool didn’t break, but breakage is very common with longer tools and adds to the overall cost of the part.

Generally, parts with these requirements may necessitate the use of extended-length tooling:

• Engraving within a pocket

• Undercuts

• Long pinholes

Reach out to the team at our precision machine shop to learn our DFM recommendations for these challenging features. We may be able to help you achieve your goals without incurring excessive costs or lead times.

3. Features Requiring Custom Tooling

Our talented partner network includes custom tooling vendors who do phenomenal work! Even so, making a custom tool is a time-consuming and expensive endeavor.

If you need complex, intricate features such as T-slotted chain guides or the pictured O-ring grooves, it can take 2-3 weeks for us to acquire the custom tooling—and it won’t be cheap. Maybe you can justify the added cost of custom tooling for a high-volume order. But if you just need a one-off part or prototype, the cost-per-part will be exceedingly high. 

Our Precision Machine Shop Is Here to Help

No matter what kind of part, feature, or tool you need, Accurate CNC Services is here to help! We love the opportunity to collaborate with our customers on unique part designs. We’ll gladly help you develop solutions that get you the parts you need as quickly and cost-effectively as possible.

Get a quote today!