What Can You Cut With a Hotknife?

A question a lot of people ask us is, “What can I cut with my hotknife?” We thought that we’d not only answer that question, but also give a quick demonstration of things that cut nicely and things that don’t.

As a general rule, if the material is fully synthetic (man-made), then it will cut well with a hotknife. Examples of synthetic fabrics include acrylic, polyester, nylon and polyolefin.

However, there are exceptions to this rule. For example, vinyl is a synthetic material, but cutting it with a hotknife is not a good idea. The hotknife melts the vinyl too fast, leaving an unsightly edge — not to mention that melting vinyl smells terrible. Acrylic fabrics with a vinyl backing can be cut with scissors without the material unraveling. The same is true for Dacron® Sailcloth. Morbern®, Stamoid™, Naugahyde® and Ultraleather® are other synthetic fabric brands that you should cut with scissors.

It’s best to cut natural materials with scissors as well. Natural fabrics don’t have any material in them that will melt with the heat of a hotknife. Instead, they tend to burn. Cut cotton, linen, bamboo and other natural fibers with scissors or a rotary cutter.

What about blends — fabrics that contain a mix of natural and synthetic fibers? If you’re working with a blended fabric (for example, a polyester/cotton blend), your best course of action is to test the hotknife on a scrap piece of the fabric first. If the knife cuts the fabric smoothly, with no issues like smoking or a bad smell, it’s safe to use the hotknife on your project fabric.

But if the knife smokes, the fabric starts to smell or you can see any fibers smoldering, it’s better to use scissors or a rotary cutter for the blend. There’s no clear percentage ratio (for example, 5% natural fibers and 95% synthetic fibers) for whether a hotknife is safe to use on a blend. You’ll have to test each blend individually to decide what the best option is.

Take a look at our roundup of some materials that work well with a hotknife and some that don’t.

Materials to Cut With a Hotknife

• Acrylic fabrics (like marine grade fabrics).
• Polyester fabrics.
• Nylon fabrics.
• Synthetic webbing.
• Synthetic rope.
• Zippers.
• Some blends — requires testing.

Materials to Avoid Cutting With a Hotknife

• Cotton.
• Linen.
• Bamboo.
• Vinyl.
• Leather.
• Some blends — requires testing.

Sailrite® Hotknives

We have two versions of the bestselling Sailrite® Edge Hotknife. The original Edge (#103800) is corded and the Edge Cordless (#122177) is not. The cordless version comes with two rechargeable lithium-ion batteries. Both hotknives perform perfectly and cut synthetic materials with ease — but if you need the ultimate mobility of a cordless hotknife, we recommend the Edge Cordless.

Did you know you can't use a hotknife on just any surface? The heat from the blade will damage and scar tables and floors. You need to place a sacrificial surface beneath your fabric, webbing or rope to protect both your work surface and your blade. The Sailrite® Tempered Cutting Glass, available only at Sailrite, is the perfect companion to your hotknife. It protects your table or work surface, and its size enables long, precise cuts.

Tempered glass is a type of safety glass that is manufactured to be stronger than regular glass. When tempered glass breaks, it crumbles into small chunks instead of splintering into jagged, dangerous shards like normal glass does. This makes it much safer to use and keep in your work area than normal plate glass.

Now you can make an informed decision before using your hotknife during your next project! What do you use your hotknife on most often? Share your experiences in the comments below.

Footnote:
This blog was updated in May 2020 to reflect new products and recommendations. It was updated again in August 2022 to add information about cutting synthetic blends.