I’m not sure what the best name for this is – heat cutting, hot knife, hot cutting – but the idea is simple: Cut synthetic fabric and seal the edge at the same time. If anyone has been caught sitting a bit too close to a fire in some nice nylon pants and gotten a spark on them, you would know that the pants didn’t burn or smoulder, but they quickly and efficiently melted in the exact place where the heat made contact. It is this property that allows us to use a hot knife (or in my case a soldering iron) to essentially melt the fabric as if cutting it with scissors. Once the cut is made, all of the raw edges are seared and won’t fray.
I’ve worked on two projects using this cutting method, each with fabric on opposite ends of the synthetic spectrum. The first was the chalk bucket, using 1000D Cordura, and the second was a pillow cover, using 30D nylon (which will hopefully be a post soon). I’ve learned a couple of things, and I thought I would share it.
First are the pieces needed. The two things I am using are a pane of glass measuring 30″x36″ and a soldering iron purchased from the local Home Depot. The total cost is about $35, give or take. It isn’t the cheapest way to cut fabric, but if you are dealing with lightweight synthetic fabrics on a regular basis, and I would say most UL MYOGers are, it can be worth it. The soldering iron comes with a few tips, but one of them comes to a nice point and works well for cutting. It is hot enough to cut through even the 1000D with just two pretty easy strokes. The glass is meant to give a heat resistance surface to cut on to protect your table. The combination works very nicely together. One other thing I use is a wetted sponge, to help clean the tip of the iron.
Another tool I am regularly using is a 12″x8″ metal carpenter’s square. What I have found is that with heavy fabrics you can free hand just about any shape you want while cutting. However, with 30D fabric, cutting along the length of the ruler is the safe bet. With some practice, I think free handing it will be possible with lightweight fabric, but using the ruler was very quick and efficient. By getting a metal one, you can have the tip of the soldering iron right next to the ruler and not worry about accidentally getting more than you meant. By getting one with a right angle, measurements are easier to make, and you can also use it for cutting corners out like the below.
Another tip I can give is that if you need to cut a segment longer than your ruler, you should cut it, then peel is back before moving the ruler. This way the cut line stays consistent, and you will know if there are any spots that you missed or melted, then meshed back together, which can indeed happen.
One important thing to remember is that the iron is hot – hopefully 900 degrees if the box tells it true. So this is a bit more dangerous than cutting fabric with scissors. There is always the possibility of melting fabric you didn’t mean to or burning yourself. Be sure to treat the iron with respect. Oh, and it is best to keep a window open to let everything air out.
I gain two benefits from hot cutting over scissors. The first is efficiency. This may be a perceived benefit, but my cutting goes about much more quickly while hot cutting for some reason. The second, and more important, is that my pieces no longer fray as I try to sew up my project. With some fabrics it seems like a race to complete the project before I lose an inch of fabric. But once the fabric is heat sealed, it won’t fray (as easily) and gives me time to work methodically on my project.
I think this was a good purchase for future projects, and I am excited to keep trying it out. I’ll be sure to update the blog if I learn anything important as I go.