Bantam Tools Blog

SVGs and Milling Metal Cutouts Without Breaking End Mills

Posted by Emily Shore on Jul 13, 2017 11:41:35 AM


Using SVG files is an easy way to mill simple shapes without using traditional CAD and CAM software. When you use SVG files, you can create your design using clipart, screenshots of images, hand drawings, or your graphic design software of choice, such as Illustrator or Inkscamilling-tensile-test-specimens-in-the-classroom-img-1.gifpe.

For more about the entire workflow for using SVGs, check out our SVG Dog Tag tutorial. Once you import your SVG file into Otherplan, you can then mill your design using any of the materials that the Othermill or Othermill Pro supports, from softer materials like machinable waxes, wood, and plastics to harder materials like brass and aluminum.

Despite the relatively simple workflow, sometimes you can run into difficulty when using SVG files to to mill harder materials, specifically when milling deep cutouts or channels in thick metal.

For instance, let’s say this is your design. You want to cut out a 1.0" (25.4 mm) diameter circle from a piece of 0.25" (6.35 mm) thick aluminum.

one inch circle.png

Typically, with SVG files, if you want to cut out a shape, you select the “Cutout” option in Otherplan, and the stroke or outermost shape in your design will be milled all the way from the top surface of your material down to the bottom, through the full material thickness.

cutout selected.png

One common problem with using the Otherplan “Cutout” option to mill all the way through the thickness of the material is that as the end mill goes deeper into the channel where it's milling, the side of the end mill starts to rub against the walls of the material  because the channel is the same width as the diameter of the end mill.

Especially with harder materials like metal and brass, the rubbing of the end mill on the side of the channel creates friction that can dull or break the end mill, or even cause the tool to encounter enough resistance that the Z-axis loses its orientation. When the Z-axis loses its orientation, the resulting cuts will have the incorrect depth. With the “Cutout” option selected in Otherplan, there's no way to alter the toolpath to avoid this issue.

Improved Workflow to Mill Metal Cutouts

In order to get around this issue, we came up with an alternate workflow you can use to get Otherplan to cut metal cutouts and channels with ease. In our workflow for using SVGs to mill through metal, we use the “Engraving” option to mill all the way through the thickness of the outline or channel of the design. Instead of milling a channel that is equal to the diameter of the end mill, as is done with the “Cutout” option described above, we use Otherplan’s “Engrave” option to mill a channel that is slightly wider than the diameter of the end mill. This added width gives the end mill more space to move and reduces friction with the walls of the material, providing better cuts and reducing wear on the end mill.

For instance, if we're using a 1/32” (0.79 mm) flat end mill, we would add an extra 0.010” (0.25 mm) of space to the channel we're milling, making the channel 0.041" (1.04 mm) wide. This extra space provides room on either side of the end mill as it progressively gets deeper into the channel, greatly reducing the friction on the sides of the end mill and enabling a successful cut.

Step-by-Step: Widening the Channel

Let’s return to the example mentioned above, where we want to mill a 1.0” (25.4 mm) diameter circle from a piece of 0.25” (6.35 mm) thick aluminum. We're going to use a 1/8” flat end mill to cut this circle out of the material. We want Otherplan to use the “Engraving” option to mill a toolpath that is the diameter of the tool, 0.125”(3.17 mm), plus 0.010” (0.25 mm) of extra space. So the resulting toolpath should be 0.135" (3.43 mm) wide.We’ll be using Illustrator in this example.

Step 1: After opening up your SVG file in Illustrator, change the stroke weight to be 0.135” (3.43 mm). (You can change the units in Illustrator in the Preferences > Units menu if you're not already in inches). Set the fill to be blank (white with a red slash).


Step 2: Next, align the stroke around the outside of your path by clicking on Stroke, and then selecting Align Stroke to Outside.

align to stroke outside.png

Step 3: Turn this new stroke into a shape that has a fill by selecting Object > Path > Outline Stroke. Now your shape should have a fill that is 0.135” (3.43 mm) wide, but it won't have a stroke.

outline stroke.png

before and after outline stroke.png

Step 4: Save your SVG file, open it in Otherplan, select "Engraving" in Otherplan ("Cutout" not selected), and choose a 1/8" flat end mill. Do not use the preset 1/8” flat end mill, but instead use Otherplan’s Tool Library to create a 1/8” flat end mill with feeds and speeds that are safe for the material you’re milling.

To learn more about this process, check out our Tool Library Guide, then go to our Materials Guide to download the custom tool library for your material, and then import the library into Otherplan.

Step 5: In this example, we want to cut through the full thickness of our stock. So make the "Engraving Depth" the same as the value entered for Material Thickness (Z). As always with metals, it’s very important to use digital calipers to measure the thickness of your material, and don’t forget to add your tape or fixturing thickness in the Placement (Z) field.

measure with digital calipers.png

The final setup in Otherplan will look something like this:

setup select engraving not cutout .png

Now you are ready to start milling!

Note: When you're milling through thick materials, to determine how deep your cut can be, it's essential to keep in mind the length of the cutting surface on your end mill, known as the flute length. With the end mills we sell, the flute length is three times the end mill diameter. So, for instance, a 1/32” flat end mill has a 3/32” flute length and will therefore work best to cut pockets 3/32” or less. If you use a 1/32” end mill to mill depths larger than 3/32”, the end mill will no longer fit in the pocket being milled.

Questions or feedback? We're here to help! Got a neat Othermill-related project you've made? We'd love to see it! Either tag #othermill on social media or drop us a line at

Topics: SVG Files, Tutorials, Tips & Tricks, Projects, Metal