How to Cut Carbon Fiber Rods

Carbon fiber is a very inert substance. It resists most solvents, and even getting the fibers to burn takes some work. In most contexts, this inertness makes carbon fiber very safe. However, if carbon fiber dust gets lodged in your lungs, the stuff stays there and can cause some nasty complications.

If you need to cut a carbon fiber rod, it's tempting to whip out a Dremel and quickly slice through the rod. Don't do that! Not only does cutting with a high-speed cutting wheel release large amounts of carbon dust, it also heats and shreds the epoxy that binds the carbon strands together. Some kinds of epoxies produce some rather toxic dust under these conditions, and you never know what kind of epoxy went into a given rod.

Fortunately, there's an easy method of cutting carbon fiber rods that releases very little dust and does not heat the epoxy. This method works well for rods up to about 4mm in diameter.

Start by finding a well-ventilated area in which to perform the work. I wear a dust mask as an additional precaution, but that's not strictly necessary at this scale.

Mark the location on the rod where you want the cut to be. I like to use a dot of white-out. If cutting to a precise length is important, make sure the mark is about 0.5mm beyond the target length to account for material lost during cutting and sanding.

Next, lay out a vinyl cutting mat, and lay a wet paper towel on top of the mat.

Place the rod on top of the wet paper towel, and place a sharp razor blade on top of the rod at the point you marked earlier.

Move the razor blade forward and backward, rolling the carbon fiber rod forward and backwards against the tabletop while maintaining gentle downward pressure. The blade will cut through the individual strands of carbon one at a time. Rolling the rod over the wet paper towel will cause the rod to be continually damp. Carbon dust will stick to the damp carbon fiber rod, then transfer to the wet paper towel.

After a few minutes of rolling, you will have cut nearly entirely through the rod. Carefully break the last few strands of carbon fiber holding the two sides together.

The end of the cut piece should be fairly smooth, but a few strands of carbon fiber may stick out a bit. Place a sanding block vertically next to the wet paper towel and smooth off the end of the rod with a few downward strokes. I generally use 300-grit paper for this step.

Once that step is done, you'll have cut the carbon fiber rod cleanly and accurately while releasing minimal dust into the air.