Making a marking knife from an old planer blade – part 1 | Popular Woodworking Magazine
 In American Woodworker Blog

A marking knife is one of the most useful tools in my toolbox. I use it to score lines in preparation for sawing or chiseling. I own several knives but the one I use most is the new slim blade Veritas knife. Last week I made my first marking knife from scratch. It all began when I replaced the blades in my portable planer.
Theses blades are made from fine grade carbide and are very tough. Whenever possible, I always try to reuse things and so, when I looked at the old blades, I scratched my head and wondered how I could repurpose them. I had two ideas: one was to make a marking knife and the other one to make a tiny chisel.

Once I identified what I wanted to do, I had to find out one important fact: can these blades be sharpened, and with what kind of sharpening medium?
I first tried the grinding wheel (I have the Norton 3X) which didn't even scratch the blades. Then I tried our DMT diamond stones and was relieved to discover that I could sharpen the blade relatively easily. Here is a picture of a sharpened blade near one that has not been sharpened. I was able to obtain a keen edge with the 1200 grit stone so I didn't attempt to use my polishing water stone as I would normally.  Also, my disappointing experience with the girding wheels taught me a lesson: Carbide yields only to Diamonds. 

Next I continued to make the handles. I chose Rosewood and grooved the two halves of the handle (to nest the blade in) on the table saw. 

I tested the fit, cleaned the grooves with a narrow chisel and prepared the parts for gluing up with Epoxy adhesive.  

Next time I will show how I finished the knife. 

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