I have made quite a few marking knives in the past for myself and other woodworkers and over that time the designs have improved in my estimation. This latest one is an ergonomic design with more of a traditional knife blade, like the Stanley knife that Paul Sellers uses for his marking routines.
Most of the knives I've made used a one sided beveled knife blank that you commonly see as a marking knife. A big advantage of those is that, because of its bevel, the blade tends to push itself into the edge of a straight edge so it's less apt to wander along uneven wood grain. The disadvantage of a beveled knife like that is it won't cut or slice like a carving knife can.
This latest knife I put together can be used as a marking knife and also will slice and carve similar to a pocket knife. Its handle is an ergonomic design and feels positive in the hand which helps in guiding the blade along a straight edge.
Once you gather all of the materials you need for the knife project, it can leisurely be put together in an afternoon. While the handle can be cut with a coping saw, I would recommend using a band saw or scroll saw, it's a lot easier.
Anyway, here's what I came up with for this marking knife...
The knife blank started out with O1 oil hardening tool steel 1/16" x 1/2" marked out with a Sharpie pen ready for cutting/grinding to the final shape. The wood I used for the handle is maple.
Rather than using a hack saw, I find it easier to use a diamond cutting wheel in a rotary tool. Grind half way or so, then bend back and forth to snap off.
The rest of the blank was shaped using a 6" grinder...
Here is what the blank looks like after final grinding. The best way to achieve the final knife profile shape is with a belt sander, using a fine grit (320 or so). I have a HF 1" x 30" belt sander and found it's perfect for getting the final knife shape.
This shows the knife handle templates mounted for cutting on the band saw. I don't use spray mount adhesive but choose to use the safer rub on water soluble glue in the tube. I can't stand using a foul spray mount.
I cut the slot for the blade using the band saw, which got the slot close to the thickness of the blank, carefully drawing the stock for the handle back and forth through the band saw until I got close to the blank thickness. Then I used the O1 tool steel to "scrape" the slot to final thickness.
Using the band saw I sliced the handle vertically. Then I attached the two halves back together using double sided tape (carpet tape works best) then cut the horizontal profile.
Once the handle is finally cut out, use whatever means you are comfortable with to complete it's final rough shape. I used the HF belt sander and it works well for me, but you might want to use files and rough sandpaper to come to a your final handle result.
I don't show it, but you want to cut thin strips of like wood to insert and glue into the knife slot above and below the blade blank. That way the blank is "locked into it's own slot and can't move.
Heat treating the knife blank is straight forward. Using a Map Gas torch, heat the cutting portion of the blade until cherry red (about 5 minutes in the flame) then immersing it into oil (I use vegetable oil). Clean off the black oxidation, roughen the part of the blank that is inserted into the handle with course sand paper (for better epoxy grip).
Here's what the knife looks like finished. Like I said earlier, it's not difficult to make and when finished you'll love how it performs. If you want a cutting template, I have put up a pdf you can print out and use for cutting out the handle and blade blank profiles. You can get it here