Most hand held pencil sharpeners work great when they're new, but as they dull they start to tear the wood instead of shaving it, and break the lead instead of sharpening it. This tool extends the life of the blades before buying new ones.
The hard part of sharpening these blades is holding onto them. The tool has a shallow rabbet and a thin clamp to allow the blade edge to be dragged over some fine sand paper and a strop. I use 400, 600, and 1000 grit paper glued to a 3/4" board, and a leather strop with polishing compound on it.
Step 1: Materials:
scrap wood (3/8" x 1" x 7.5"), (3/4" x 3" x 5.25")
aluminum bar (1/8" x 1" x about 5")
knob bolt (1/4"-20 x 1/2")
tee nut (1/4"-20)
bolt (1/4"-20 x 3/4")
nut (1/4"-20) w/ nylon insert
little spring (3/8" long)
Step 2: The Rabbet
The rabbet that the blade slips into needs to be shallower than the blade thickness, and narrower than the blade width. Most good blades are .030" thick. Some cheap ones are only .020" thick. So if you can dial in about 1/64" deep, you're good. Practically, a little trial and error is necessary. I cut mine on the table saw with the saw blade barely showing. Then I put in the sharpener blade to check the fit. It took me a couple tries.
Step 3: The Clamp
The aluminum bar has a little bend in it at the back end. Put it in a vise and tap with a hammer. The front has sharpish bevel on the front. I did it on a belt sander, but a file would work just as well. You're going for a smaller bevel angle than what is on the blade, since it needs to be able to clear the sandpaper. (It's hard to measure, so I just eyeballed it.)
Step 4: The Sanding Board
I used 3/4" MDF since it is very flat, and glued small sheets of sandpaper to it. (400, 600, 1000 grit) For the leather, I used a scrap, and glued the smooth side up and rubbed some polishing compound on it. Some people put the suede side up. I don't think it matters very much.
As an alternative you could use a sharpening stone or stones. They should all be the same thickness though, since the thickness determines the angle of the blade on the stone.
Step 5: The Rest
I determined the height of the backrest by holding the arm with the blade edge just touching the sandpaper, and measured how tall the back would have to be. Mine is 5.25". The arm is 7.5" long. Then I drilled and screwed the two pieces together with some wood glue. Before the glue dried, I fine-tuned the angle with a bright light behind the blade until the edge of the blade touched the sanding block evenly. After the glue was dry I took the screw out and replaced it with a dowel glued in and added some miscellaneous scraps to reinforce the joint.
Step 6: Using It
You don't want to overdo it, because if the blade gets smaller it affects the pencil sharpening adversely. It only takes 3 or 4 gentle swipes across each grit, and maybe 6-8 firm drags on the strop. Cheers. You just saved a few pennies on the cost of a new blade...
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