This concept can be transferred to just about any handheld tool, so even if you don't need a craft knife, it still may be helpful for you. The idea came about when I needed a knife for paper crafting, but wanted something other than the usual pen style. Instead, I wanted one that gave me more control and didn't give me hand cramps to use (low cost was also a goal). With a few household items and about 5 minutes of labor, I ended up with a blade that molds perfectly to my preferred hand position and has been a joy to use over the past few months. So, here's how you can make your own. It's extremely simple.
Step 1: Materials
You need 3 things:
- A blade -- I'm using a replacement blade from a utility knife. It's the kind that has two sharp ends and can be flipped over when one edge gets dull. Mine looks dirty here because I'm making the tutorial while I flip the blade over to get a new sharp edge.
- Reusable weatherstripping -- This is the pliable kind that comes in a boxed roll. It shapes easily and stays soft.
- Tape -- I'm using basic masking tape, but any tape that is flexible and sticks to itself will work. Masking tape is good because it's easy to remove if you need to adjust the fit or flip the blade.
Just a note about the weatherstripping... Mine has a warning on the box that says it contains a chemical that is known to the state of California to cause cancer, birth defects, or other reproductive harm. Many household items have this label. In this project, you're handling the stuff for a few minutes and then covering it with tape. Proceed at your own risk. At a minimum, wash your hands afterwards.
Step 2: Begin Covering the Blade
Like I said, this project is very simple to do. The magic is in how it works once it's all together. All we're going to do is cover the blade with the weatherstripping, then wrap it with tape.
I started with pulling off a chunk of the weatherstripping and rolling into a log shape to cover the sharp part of the blade. You can cover the entire edge if you want to reduce the risk of getting cut while you're making it. Otherwise, cover all but the amount you'll want exposed for cutting.
Continue adding weatherstripping material until the blade is covered in a thick layer, paying extra attention to sharp corners that may poke through.
Step 3: Test the Fit and Adjust
When you think you have the blade sufficiently covered with weatherstripping, try it out. Find the position(s) you think you will use for cutting, and see how it feels in your hand. As you can see in the photo, I pinch it between my thumb and middle and ring finger, and press my index finger on the slope at the top. When I cut like this, it feels like the blade is part of my hand and I'm just tracing with my finger. I sacrifice a tiny bit of visibility for ergonomics, and it works for me.
Find your favorite grip and put pressure where your fingers will touch the knife. You'll feel it squish slightly under the pressure, creating indents around your finger. The indents help to support your finger, but you may want to build them up further so the material doesn't get too thin. It will continue to shape itself with your hand after we put the tape on, so don't try to get it perfect. Just give it a head start.
Step 4: Wrap With Tape
When you're happy with the fit, begin wrapping the knife with the tape. I don't have a special technique here. The most important thing is not to wrap it so tightly that there's no room inside for the weatherstripping to squish and conform. Different tape may perform differently here -- masking tape doesn't stretch, so it's easy to control the tension. Other than that, just get it covered well, remembering to keep the cutting edge of the blade exposed. I'm not picky about how my tools look -- I'm sure some of you can make much nicer ones with prettier tape and no bunching.
After you get it wrapped, test your grip again. Do some test cuts, if you want. The idea is to continue forming the indents so they support your fingers comfortably. See how much movement you get, and if any of the weatherstripping squeezes out between the seams of your tape. Add more tape, move things around, smooth edges, and so forth until it feels right.
Step 5: Enjoy!
At this point, you're done creating the knife -- it's really that easy. It will continue to conform to your hand as you use it, and never harden. If the weatherstripping ever squishes too far out of place, just push it back where you want it. I've used mine for several months and only had to adjust it once when I was using more pressure to cut thicker material. I added more tape once, also, because an edge of it had peeled up where it rubbed my finger. Now that I've learned how it responds to use, I can create it differently from now on to reduce even this little bit of maintenance.
As I mentioned, when the blade starts getting dull, you can just peel off the tape and squish the weatherstripping around to expose the other edge of the blade, or take it off and reuse it with a new blade. Then just re-wrap with fresh tape.