I like this project because the process is fun, the product really is useful, and it's a simple way to get to know tool steel.
(It even includes some blade making techniques!)
I used a piece of old bandsaw blade, 1in wide, which was too chewed up to be repaired. It's good steel - springy but holds an edge (see: SAW.) And this material is FREE if you know where to look.
I like to sew, so the seam ripper is a must for cutting out stitching mistakes. Nice to make my own.
I made this at TechShop Detroit. I'm a big enthusiast. Here, check it out: www.techshop.ws
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Step 1: Tools and Materials
- Scrap bandsaw blade
- Markers/carbide scribe for marking the outline of your seam ripper (Don't hesitate to free-hand! That's what I do.)
- Square/straight edge in case your free-hand ain't so free
- Gloves for handling the blade
- Angle grinder with abrasive cutoff wheel
- Disc sander
THESE HAVE BEEN PUT TOGETHER ONLY FOR THE PHOTO. The table of one tool is NOT a work station for another tool. But you already knew that.
Step 2: Cut Up Your Bandsaw
Think about your bandsaw blade material for a moment... It's designed to cut metal, so it's going to be harder/tougher than most other metal.
Using a bandsaw blade to cut another bandsaw blade is at LEAST inefficient. It will also likely result in a second damaged blade.
The basic story about "tool steel" (steel alloys used for tools) is that
- it is generally harder/more durable than mild, "I bought this at the hardware store" steel
- it can usually be heated in certain ways to make it EVEN HARDER/MORE DURABLE.
We want to keep whatever properties our scrap blade already has. So we'll cut it in a way that makes sense to cut many tool steels: with abrasives. This way, we're grinding away metal instead of trying to chew it with blades.
First, throw your blade onto the open floor, so it springs open without the risk of hurting yourself.
Then clamp in the vise and use a cutoff wheel to score the material MOST of the way through, and not very far above the vise.
Finally, with gloves on, pull the blade TOWARD YOU until it breaks at the score. If you push away, when the piece snaps off, you might rake your wrist over the material left in the vise.
I made two such cuts - one to open the loop of the blade, and another to cut a piece of workable material.
Step 3: Draw the Seam Ripper
I used a fine tipped marker to draw out a ripper with a hooked blade and a generous handle. Make a few, if you like, to handle different threads or specialty shapes to get at hard to reach seams.
(I held the blank in my hand to get an idea of the handle size. Why should it be this tiny thing?)
Step 4: Cut and Grind to Reach the Profile
Again, we're working with tool steel - we don't want to use cutting or shearing tools because they will get damaged. Files are also a bad idea. Think of what you can do with grinders, sanders, cutoff wheels, and sandpaper - consumable grinding tools.
FIRSTLY firstly, I used the disc sander to remove the bandsaw teeth. Move the work side to side to get an even surface, and to wear the sanding pad evenly. NOTE ABOUT THE PHOTO - for actual sanding, the material should be positioned where the blue outline is. In this way, some of the material is supported all around by the work table, so there' much less risk of the part being pulled in by the blade.
Next, I stacked my piece on some sacrificial wood and clamped them both to the table. I used the cutoff wheel to make straight cuts off of the material.
Then, I ground an accurate profile: the long edges on the disc sander; the concave blade on the edge of the disc sander*; rounded corners on the sander or grinder to make the tool comfortable
Finally, I used the wire wheel VERY CAREFULLY and with A GREAT DEAL OF RESPECT to remove the burs left from all that sanding and grinding.
---All of this grinding friction will produce heat---
You can dip your work in water to keep it cool, but always work with bare hands. It's the only way you can feel your material.
Another issue with heat is that you don't want to ruin the heat treatment on your material! That hardening treatment I mentioned earlier. The last photo demonstrates the peacock colors resulting from overheating your steel. Work patiently and keep it cool.
* Using the edge of the sander makes this project pretty advanced. You need to be very comfortable with the behavior and limitations of this tool - and of steel - before you try this technique. I'll say this again when it's time to sharpen the blade.
Step 5: Grind a Cutting Blade
We're going to push back the guard on the disc sander to get at the edge. This is an advanced move! If the sanding pad is damaged or worn at the edge, it will give you poor results and could harm your machine. Please be honest with yourself: "Do I know what I'm doing?" If not, better to find someone to show you the ropes.
Anyway, expose the edge of the disc sander - this is how we'll grind a concave cutting edge. Hold your work at an angle to the sander; your going to (gently) use the edge of the sanding disc. The motion is to rotate the piece while pulling it from left to right - check out the photos. This takes practice and a little intuition.
Your aim is to create a sharp, two-sided bevel that meets in the middle of your blade. I.e. a cutting edge!
Notice that, in order to keep the same left-to-right motion, I have to flip the piece over to do the other side.
Step 6: Sand the Cutting Edge
The disc sander will leave a rough, burred edge on your blade. Use sandpaper (NO FILES please) to smooth it out and sharpen it.
I flipped all my wet-dry sandpaper over so you can see the grits. The higher the number (220, 320...) the FINER the grit.
I cut strips of sandpaper and taped them around a round pencil to fit the blade curve. If you wrap a few thicknesses, you can peel away worn paper to reveal fresh stuff. Please don't use scissors to cut the sandpaper! Score it or fold it to cut - I've got an instructable for that if you're scratching your head.
Go through all the grits: the sander was 100-series, so 220, 320, 400, and 600 - the blade will be smooth and start to look kind of polished. If you're sanding with even strokes, then your blade is coming to a rather nice edge. I've found your ripper doesn't need to be razor-sharp to be useful, but feel free to follow any blade sharpening techniques you'd like for a sharper cutter.
Step 7: Done and Done
You've got a seam ripper AND a nice introduction to tool steels AND blade making. A three-fer.