Drill File CAM Configuration

Table of Contents

Our service cannot process Altium’s Drill Drawing (DD1) or Drill Guide (GG1) files. We need the drill file to be in NC Drills format file. Altium typically generates these with a .TXT extension.

Altium has published a guide on producing those files here: http://wiki.altium.com/display/ADOH/NC+Drill+Output+Options

The drill format options we use are as follows:

  • We prefer a 2:4 format when using Inches, or a 3:3 when using Millimeters. Some versions of Altium do not have these options, so you should use 3:4 in Inches, or 4:4 in Metric, and verify that the drill hits align correctly on the previews.

  • Check Keep Leading And Trailing Zeroes

  • Generate Seperate NC Drill files may be checked or unchecked. We will merge drill files automatically.

  • Use Drilled Slot Command may be checked if you wish to include in your design. See our slots page for noted restrictions on using drill slots.

  • Uncheck Generate Board Edge Route Paths. We do not use provided edge-milling paths, and including them may have unexpected results if they’re used for manufacturing.

  • For Coordinate Positions”, you’ll typically check Reference to Absolute Origin. However, since this option needs to align with a similar CAM setting for the gerber files, consider changing it to Reference to Relative Origin if your gerbers appear incorrect in our previews.

  • Optimize Change Location Commands doesn’t matter, as we will recalculate drill movement.

In some cases, including the binary .DRL file will cause us to reject the board even if you have a .TXT file in NC Drill format. Deleting the .DRL file will resolve that issue.


The following image shows a properly aligned drill file, and should resemble your previews when uploading your board. If anything looks strange, consult our Drill Troubleshooting Guide for some tips or email [email protected] for assistance.

Correctly Aligned Drills

2 layer Drill Specs

  • Minimum 10 mil (0.2540mm) drills with 5 mil (0.1270mm) annular rings. | Minimum 20 mil (0.508mm) drill slot slot size
  • Maximum plated hole size is 265 mils (6.7310mm) Unplated holes do not have a maximum size.

4 Layer Drill Specs

Spec Size
Minimum annular ring 4 mil (0.1016mm)
Minimum hole size 10mil (0.254mm)
Minimum slot size 20mil (0.508mm)
Maximum plated hole size 260 mil (6.604mm)
Maximum non-plated hole size None
Via plating thickness 1mil (0.0254mm)
Blind Vias No
Buried Vias No


Fabrication Tolerances

Drill Tolerances

Spec Maximum Typical
Drill size variance Max +/- 2.5 mil +/-1.5 mil typical
Hole positional variance Max 2.5 mil <1 mil typical
Stop Mask alignment Max 3 mil <1 mil typical

The hole diameter after plating will be within +/-2.5 mil of the drill size specified on the drill file, although it’s typically within 1.5 mil of the size specified. For tight-fitting components, it’s important to note this spec, and make sure that the component will still fit if the hole size shrinks. If the hole grows, it typically does not present a problem since it simply reduces the annular ring slightly.