|Many of us have purchased the Tri-Sharp Rotary Blade Sharpener [see photo link above]. It works well on the first few blades sharpened, but then it wears out and doesn't seem to do the job anymore.
First, let me point out that this tool is ingeniously designed. The part of the tool that grinds the blade to sharpen it has the correct pitch or angle, so the blade is sharpened correctly. The handle that holds the blade is a wonderful design too, making it so the task can be done safely.
The problem is, in order for the manufacturer to make this tool inexpensively, they used sandpaper instead of a 'wet stone' for grinding the blade. A wet stone would last almost forever, but given the design and pitch needed for a circular blade, it would have made the tool way more expensive. Also, a tool that lasts forever doesn't make for repeat sales.
By using a wet/dry sandpaper, the tool can be made very very cheaply. Unfortunately, sandpaper of any type wears out quickly. This makes most people think this tool is a piece of junk. It's not! We just need to replace the sandpaper.
At first I thought we'd need self-adhesive aluminum oxide sandpaper, but I haven't found it in a sticky-backed. Here are the 3 things you need to fix this tool:
Wet or dry sandpaper, 400 grit [3M Imperial aluminum oxide is the best]. This is better than what the tool had originally. I found the package shown in the link above, at Walmart in the automotive department. It costs less than $3 and has 5 half sheets [which makes 85 replacements for a 28mm cutter!]. I also found it listed at Ebay.
Glue [even better, a glue stick...better yet, a temporary glue stick].
Small pointed scissors.
Trace the O-shaped sandpaper that's currently on your sharpener, and make a cardboard or template plastic pattern [something stiff enough to trace around].
Trace this pattern on the back side of the sandpaper, over and over [see main link above], then cut the shapes apart. It's important that the inside of the circle is cut big enough to slide easily over the sharpener's handle as shown here. The outside circle just needs to be big enough, and doesn't need to be cut perfectly.
Tip...it's easiest to cut the inside circle first, while you have more paper to hold on to.
Remove the old black sandpaper on your sharpener...it should peel off easily. If it won't come off, just leave it and glue the new ring of sandpaper on top of it. Over time, as more and more layers of sandpaper accumulate, you may want to soak them all off in a basin of warm water. The tool is plastic, so soaking won't hurt it.
I left the old beige sandpaper on the other side, to now be used as the finer, finishing side. I'm not convinced that the use of this side is even necessary.
Voila, all fixed!
Rotary Sharpener Tips
The directions for this tool say to twist the blade a few times on each side of the blade. This really depends on how hard you push, and how dull your blade is. I twist the blade back and forth as I count, that way I know to count to the same amount after flipping the blade. A really dull blade may take to the count of 40 for each side. I think this is another reason many people thought this tool was no good...they didn't sharpen long enough.
A tiny drop of oil may be used with this sandpaper, so I've got an insulin syringe [ask a diabetic friend for one] filled with oil in my kit, for convenience. It's also good to give your rotary cutter a tiny drop of oil so it turns freely.
After sharpening, I test for sharpness on a scrap of fabric, while the blade is still in the sharpening handle. Use both hands to hold the tool's handle, and roll into the fabric about 1/4 turn. Reposition your hands and test the next 1/4 turn, etc., as shown here [except one hand is holding the camera ;)]. This way if it's not sharp enough, you know before putting the blade back in the rotary cutter's handle. Much easier to sharpen more, if needed.
Use a magnet to move the blade from cutter to handle and back, so you can't get cut accidentally...as shown here.
You may have noticed the red felt covered box I made for mine. That's how much I like this tool. I'll now have a place to keep the extra sandpaper O's I've cut out, so I'm ready to easily replace when necessary. This box has a unique Velcro closure as shown here. The staples really work!
Bonus Side Effect...when I was done cutting, my little craft scissors were so sharp! Apparently the cutting action through this sandpaper works the same as grinding a blade on it :)