NC Drill File: Everything You Need To Know in 2023


Along with the advancement of technologies, there is a rise in pressure in the electronics industry regarding the current Printed Circuit Boards (PCB). As many know, circuit boards act as the skeletal system of every electronic component.

In line with the advancement, there is increased demand for circuit boards in compact design since almost all devices nowadays are miniaturized. This means that its backbone size should be significantly reduced to flawlessly fit into the modernized equipment.

Since then, the pressure among PCB Designers and Engineers has substantially increased. It has been brought to their attention that they must provide a solution with regard to the design file that will correspond to the PCB Manufacturer’s requirements during the production phase of the boards. Consequently, the NC Drill File was established.

Consequently, we will thoroughly discuss the critical aspects brought by the NC Drill File to the electronics industry. Hence, we will dissect its definition, origin, purpose, format, ways to incorporate it in Altium Designer and Cadence Allegro and its setting items. We recommend reading the post until the end to grasp the NC Drill File concept fully.

Introduction to NC Drill File

Introduction to NC Drill File

What is NC Drill File?

According to some, NC Drill Files can also be called Numeric Control Drill Files. In other words, it contains information that can be used to control the tolerances for vias and drilling holes. Along with such information are the dimensions, placement, and size of the tool it necessitates.

Accordingly, the NC Drill File is essential for PCB Engineers and Designers since it speeds up the process of converting PCB files into Gerber Files. As a result, the errors conducted by the Engineers in failing to transform Gerber Files to NC Drill Files have significantly reduced since the NC Drill Files can already be produced straight away.

Typically, the PCB Engineers will export the files, and then the PCB Fabricator will modify the Gerber File into an NC Drill File prior to beginning the production process. Its procedure was designed like this because the PCB Fabricator Engineers are more knowledgeable than the former Designers and Engineers of the Gerber File. In addition, the format of the Gerber Files delivered to the Fabricator poses various issues, like different software version usage. Therefore, the specialists have created the NC Drill File and Gerber File simultaneously.

In order to fully grasp the concept of the NC Drill File, below is the sample output of it.

What is NC Drill File?

Example Coordinates

Overall, NC Drill File is essential in successfully producing the design the architects and engineers created. Thus, it is essential that it will be free from any errors.

What is the Format of the NC Drill File?

Since Excellon was the first business to create CNC (Computer Numerical Control) systems for drillers and processors, almost all PCB design tools can generate NC Drill Files in a similar systematic format. Due to its lengthy longevity and considerable contribution to PCB Drilling and directing technology, the Excellon has additionally grown to be known as a succession of industrial milestones.

Excellon is commonly used for standard CNC boring and traversal because of its capability to express equipment-specific parameters like drill feed and tempo.

Generating the NC Drill File with Altium Designer

Before commencing, right after the startup of the Altium Designer, we suggest configuring its settings to avoid problems along the way. First, click the File button. Then, select Fabrication Outputs. Lastly, choose NC Drill Files; then a dialogue box will pop up as NC Drill File Setup. In this phase, one will be given the options for the NC Drill Format, Trailing Zeroes, Coordinate Positions, and other configuration settings; set it according to the desired specifications.

Generating the NC Drill File with Altium Designer

Dialogue Box in Altium

  • Units can be set to inches or millimeters; it should align with the Gerber File requirement. If not, it could pose problems that make them ill-suited for each other.
  • Formats – It has varying alternatives, like the 2:3, 2:4, and 2.5 dimensions. Wherein the smallest value has a minor resolution, and the higher value has an excellent resolution. However, we suggest contacting the manufacturer before selecting one; they will know better which format is ideal for the purpose and application of the board.
  • Zero Suppression – It is essentially in charge of the NC Drill Files’ appropriateness and orderliness depending on the required function and comfort. In essence, if conceal commencing zeroes are chosen, the first zeroes are removed, and if suppress subsequent zeroes are chosen, the final zeroes are removed.
  • Coordinate Positions – It possesses value for its absolute and relative origin; it should coordinate with the Gerber File specifications. Since it will dictate the exact placement of the holes and components, it is essential not to commit any mistakes in configuring its value of it.

If additional components are required for undertakings, one can choose them. After making your decisions, click OK to establish the NC Drill Files, which will be saved in the document folder’s default sub-folder.

Generating the NC Drill File with Cadence Allegro (OrCAD)

The Cadence Allegro does not adhere to Excellon standards in comparison to the Altium Designer. However, their commencing process is quite similar. To begin, it is essential to configure the parameters to avoid issues during the designing phase. First off, click Manufacture. Then, select NC. Finally, choose NC Parameters, then another pop-up dialogue will appear.

  1. Initially, choose the components for the Excellon structure and export the document in the NC Parameters box. As opposed to EIA, ASCII is regarded as being a more current kind of coding, which is why it was selected for the programming in the outcome document.
  2. To create an NC Drill File with an Excellon file, it is crucial to double-check the earlier augmented Excellon format.
  3. According to the project specifications and requirements of the PCB Architect, or simply to be in compliance with Gerber Files, it is essential to select preceding Trailing Zero Suppression for negligible reduction.
  4. Once everything has settled, and all of the desired parameters are set, it is time to click the Close button. After that, the NC Parameter window will shut.
  5. Following that, the NC Drill Dialogue should emerge once again by clicking the Manufacture, then NC, and finally, the NC Drill.

Generating the NC Drill File with Cadence Allegro (OrCAD)

Dialogue Box in OrCAD

Once you’ve finished choosing your options in this window, click Drill to conclude creating Drill Files. The recently produced NC Drill Files are located in the default file folder.

NC Drill Setting Items

In a nutshell, a basic file format exists to set in an NC Drill File. It will be further understood in the underneath table; this will serve as one’s guide in generating their own file.




Either “Excellon” or “RS-274X” can be chosen.

One can choose between “mm” and “inch.”

Number of Integer Digits

One can choose the number of integer bits.
Decimal Places

One can adjust the decimal places to suit one’s tastes.



Zero Suppression

A choice of “None,” “Leading,” or “Trailing” is available.

  • The “Trailing” option eliminates any extra zeros at the end to save space.
  • To decrease the amount of data, “Leading” eliminates any zeros at the outset.

Offset X

One can customize the Offset Value for the X Coordinate to match one’s specifications.
Offset Y

One can customize the Offset Value for the Y Coordinate to match one’s specifications.





To create an NC drill file that contains coordinate data that has been inverted, we suggest using this command. Pick one of the options below using the drop-down catalog:

No Mirror:  The data about the coordinates as seen from the surface is produced in an NC drill file.

Horizontal Mirror:  An NC drill file is produced with the reference data horizontally inverted.

Vertical Mirror:  The vector data is delivered as an NC drill file that has been vertically represented and imaged.


It is possible to set the prefix at the start of the outsource file name. One can use the Board Title, date, etc.

Slot Hole Output Type

Select “Center,” “Both Ends,” “Center & Both Ends,” or “Series” as the method for exporting slot/square gaps into NC drill files by enabling this feature.

Center:  Creates a single drill in the exact middle of a square or rectangular aperture.

Both Ends:  Output twin probes to a groove or square hole’s different poles.

Center & Both Ends:  Three drills are produced at a slot’s center and both of its extremities

Series:  Myriad drills are created in a sequence at the periods defined in the Pitch Parameter.

Separate File According to Plating Status

Activate this option to create distinct NC Drill Files for holes with and without plating.

Examples of File Names:

Sample_NCDrill-TH: A NC drill file for plated drills

Sample_NCDrill-NTH: A NC drill file for unplated drills


To wrap things up, it can be complicated the in-depth details of NC Drill Files if the reader isn’t familiar with the terms utilized in the electronics industry; however, one thing that can be easily understood by many is that this particular file plays a significant role in flawlessly achieving the desired circuit board output. Hence, it is essential to configure it per the standard guidelines.

As an experienced manufacturer with over twelve years of industry experience, PCBTok has gained the necessary knowledge to efficiently produce remarkable NC Drill Files without experiencing any issues. Thus, if you intend to have your device’s circuit board designed, then look no further since PCBTok has enough skilled and experienced personnel to work these things for you. We guarantee that every bit of your penny spent on us will be worth it.

Along with that, we have an ongoing special offer for our beloved consumers. Take advantage of our discounts by having us develop your Printed Circuit Board (PCB)! Send us your requirements right away, hurry! All the time you can reach us!

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