8 Tips For CNC Machining Design Guidelines

Do you know that the CNC machining industry had raised from 80 million in 2019 to 83.99 billion in 2030? The crown of this exponential growth and success lies in the expert CNC machining design guidelines.

But what’s the role of CNC machining guidelines in the global market?

An error-free design guides manufacturers to create highly precise and efficient machine parts for successfully working complex machines.

However, designing parts for CNC machining requires careful consideration of several factors to ensure the final product meets the desired specifications and quality standards. Here we would like todiscuss the CNC machining design guidelines that you need to keep in mind .So read on!


Basic Rules When Designing CNC Machining Parts

  • Optimized Designs

Highly and professionally optimized designs reduce the labor cost and time for manufacturing a part. Repeatability is enhanced when the designs are complex yet highly optimized.

  • No Confusing Instructions

Avoid adding any vague statements and prefer to explain the details. Vague sentences may confuse the manufacturer leading to the manufacturing of a faulty part.

  • Label Dimensions On Parts

Accurate dimensions should not be mentioned in the space; instead, they should be labeled on each specific point on the parts. It indicates each length, width, and height of the parts giving direct instructions about the part’s dimensions.

  • Keep The Design Lighter

Manage to fulfill all the functional requirements of a part, keeping the design lighter. Lighter designs help to manage the production time and cost of CNC machining.


CNC Machining Design Restrictions

There are certain design restrictions that need to be followed for better results and strong parts.

Why is it necessary?

CNC machining is an expert procedure where even a little deviation from the set rules can turn success into disaster.

Check out these restrictions to avoid failure when manufacturing the machine parts.


1.Tool Geometry

Cylindrical shaped equipments are common among these machines as they are shorter in length. Most parts requiring a deeper final cut are difficult to manufacture because a cylindrical tool cannot reach the depth.

Some of the advanced tools might resolve this issue using a longer shaft. However, this comes with a huge negative issue of additional vibrations disturbing the precision and accuracy of the specific part of the machine.

What’s the exact solution?

Tools with elongated diameter and shortened length are more helpful for reducing the design restriction.


2. Tool access

CNC machines have a subtractive procedure of designing a complex machine part. A block of material is placed in the machine, and the machine starts carving the details by subtracting the extra material.

The principal direction of the CNC machine working is from top to bottom, which sometimes reduces the machine’s access to the inner cavities and vertical walls.

Then what could be done?

Changing the direction of the five-axis CNC design of the specific workpiece can help the CNC machine access the inner details.

CNC Machining Design Guidelines

1. Inner Edges

Computer numerical control machines usually operate with circular drill bits making it difficult to make sharp internal edges. The circular shape of the drill bit leaves a space behind where an inner edge was supposed to be created. With less space where the drilling machine couldn’t reach is also depicted as the internal corner radius.

If the manufacturer wants to save costs on manufacturing, then using electrical discharge machining methods for the internal edges is difficult. That’s why it’s important to avoid very sharp internal edges with less corner radius because when the corner radius is larger, it will give more room for the tool to work effectively. Another benefit is that a larger corner radius, above 0.005 inches, would help to protect the tool from premature wearing.


2. Holes

The depth of the holes has a huge role in the strength of the tool and the part being manufactured. If the drilling equipment works too shallow, it will have numerous weak points where the screws will not be held effectively.

If the drilling depth is less for the drill bit, it might experience extensive damage or even break, affecting the accuracy of the part. The size of the drill bit will determine how much depth of the hole you can maintain. The thickness and hardness of the material determine the strength, and ultimately, the allowed shallowness and depth of the drilling capacity are calculated.

According to a general rule, the depth of the hole should be almost four times the diameter of the drilling bit. It helps to manage the stability of the manufactured part and the drilling bit.


3. Threads

When manufacturing a complex machine part with a computer control machine using the CNC machining design guidelines, threads must be created at some points. These threads are a powerful and effective way to attach machine parts, screws, and fasteners.

The depth and width of the threads should be considered very intelligently because otherwise, they will not be able to hold onto the fastener or other parts of the machine effectively.

Multiple types of threads work for different material types because some of them are soft while others might be hard. A shallow thread will work better for a soft material,such as aluminum or brass , while if you’re working on a hard material,such as titanium or tool steel, keep the threads deeper for better results. When threads are specified on the drawing of the particular part for the CNC machine, it should be ensured that every detail of the thread is mentioned.


4. Chamfers & Fillets

The round corners inside the workpiece are also known as the internal fillets. Increasing the size of the internal fillets ensures the part you are manufacturing will provide high efficiency with no compromise on quality. The rounded corners inside the manufacturing part or the key points for reducing stress yet increasing the strength.

How does increasing the fillet size helps?

It helps in various ways including:

  • A very less cutting force on the workpiece that also helps with protecting the machine equipment from getting damaged.
  • The material flow when cutting it with an improved chip removal is highly important for efficient manufacturing of the particular part. And an increased fillet size helps with this.
  • The surface finish of the part and it’s build quality gets boosted.
  • There are very low chances of getting your equipment and tools damaged.

5. Thin walls

When the material is machined using CNC machining, sometimes it may reduce too much material leaving behind very thin walls. The access removal of the material puts stress on the remaining walls as they can not bear over machining. Thus resulting less tight tolerance in this part. Additionally, these thin walls will have a very low stiffness causing them to damage very easily, losing the purpose of the workpiece.

Especially when working on metals, chattering is possible with extremely thin walls as the product will lose it’s precision and accuracy. The soft, thin walls will not let you design the part effectively when working on plastic.

Then what’s the ideal wall thickness?

When working on metals, maintain a wall of almost 0.8 mm and avoid going below this thickness. For plastics, you need to keep the wall even thicker at 1.5 mm thickness, or else you cannot work on the workpiece.


6. Undercuts

CNC equipment requires open space for efficient working. That’s why a part has depressions in the corner, or you may call them undercuts. These undercuts are not easy to create because, to maintain precision, the right tool should be used to create standard undercut dimensions. A recommended value of undercut dimension is between 3mm to 40mm.

Do you know what’s the benefit of perfect undercuts?

  • It helps make the part look better from the outside and boosts internal strength and quality.
  • Mostly, tools are used with improper undercuts, affecting their working and ultimately causing premature tool wear. So perfect undercuts help to save the tool for long-term use.
  • When more depressions or spaces are available, it needs less force to apply to the workpiece to create the desired design.


7. Cavities & Pockets

The depth of the pockets and cavities created with the CNC machines should be very precised and controlled because you need to maintain the quality of the workpiece. Whether you are working with plastic, aluminium or any other metal, there needs to be a specific allowed limit for the depth with the machine equipment.

Some basic allowed depth ratios are:

Material Depth Ratio
● Plastic ● <15 times of the mill’s diameter
● Aluminium ● <10 times of the mill’s diameter
● Steel ● <5 times of the mill’s diameter

Maintaining the depth of the cavities and pockets while manufacturing a complex part with CNC design guidelines is crucial because longer equipments produce higher vibrations. These vibrations effect the structure of the manufactured parts ultimately destroying or disturbing it.


8. Text and lettering

Some clients request custom text or letter carving on the parts. It needs specific CNC machine design guidelines. When the machine puts on a text or letter, it should be ensured that the width, height, and space of the specific area of that part must be constant throughout the process. If this guideline is not followed, it may damage the part and the tool.

The size of the fonts for text also plays an important role. If you are keeping the text size too small, it would be useless as reading it would not be easy. It will affect the tool’s life and the part’s accuracy.

The solution?

Keeping the text size to standard fonts and using a simple text style will help you to keep the process smooth without affecting the part.



A professionally settled design would help to maintain the production and cost of complex machine parts. Manufacturers need to improve the quality of manufactured products together with maintaining the cost and time on the manufacturing of specific products.

That’s where design guidelines for CNC machining get in to help out.

Do you have the trouble in desgining your CNC machining parts? Try with Worth Hardware. Who we are ?We specialize in CNC machining design and manufacturing, with a wealth of experience in creating high-quality products and parts for various industries. At our CNC machine shop, we have an impressive range of machines that includes 3 to 5 axis models, and we’re backed by a team of skilled designers, engineers, and machinists. Whether your project is simple or complex, we’re fully equipped to tackle it with precision and efficiency. Trust us to deliver superior results that meet your unique needs and specifications.