Blade thickness right above the edge?

M

mark23

Joined
Jul 14, 2002
Messages
375
Hi!

After all I am to take part in the fabulous "toolmaker pentathlon": sawing, drilling, grinding, filing, smoothing. I am going to make my first knife.

I decided to make a Campknife first. Right now I am thinking about blade geometry. "Knife Class": Fallkniven A1 or Busse NO/SJ type.

What should be the blade thickness right above the edge? (How much material should be left prior to sharpening?)

According to my drafts bladethickness at the spline is 5/16", maybe 1/4", slightly convex blade profile, "height" of blade (edge to back) is 1.65"

Any suggestions? Maybe someone could take a sliding caliper, measure his Busse's, Fallknifen's, Swamprat's, etc's blade thickness right above the edge and post the value here.

Thanks in advance!!!

Regards

Mark23
 
My Busse SH II has an edge that I thinned a little (to about 20 deg/side) from the factory edge. That makes the secondary grind a little higher, and therefore a little thicker point just above the secondary edge compared to what it was coming from the factory. At the middle of the blade, it measures .050" just above the secondary edge.

I thin a lot of edges to about this value, and I've measured all of them like this. They vary from .014" to the Busse's .05. A lot though depends on the over-all grind. I have relatively thick Livesay knives made from 3/16" stock, hollow ground, at .032" behind their edge, while a flat ground E. Chang hunter that starts at 5/32" stock goes down to .014" behind the edge. Getting the grind as fine as it gets isn't easy apparantly because very few knife makers that I've been able to buy from are able to get below .018 with a flat grind (remember this is just above a 17 deg/side secondary). This includes thinner knives. I have one that is only .1" thick (that's barely under 7/64") at the spine, flat ground almost 1" wide. It's .017" behind the edge. I have a 1.5" wide skinner of 1/8" stock that is .025" behind its secondary bevel! That bevel is about 1/8" wide!

Bottom line is, it varies a lot! Keep the first knife simple and don't try to get too fine. Especially if you are after a wood chop capable edge.
 
The steel or alloy you use makes a difference, you can grind 5160 and other simple carbon steels VERY VERY thin at the edge and still have high durability, however you cannot do the same with Cpm44v because it will be too brittle, to give two extreme examples. If your want your knife to be able to effectively chop without damage, obviously you want enough material behind the edge to support it. In this case your steel choice is even more crucial, of course if you stick to steel like 5160, 0-1 or 1095 ( which are often refferred to as excellent "beginner" steels) you have much less to worry about than if you use stainless.
this would be a good questions for Shop talk too-
Good luck and report back!
Martin
 
Hi!

After all the praise I heard here on bladeforums I chose 52100E to start with. I decided to make it .045" thick at the secondary edge.

Thanks for your advice.

Regards

Mark32
 
mark :

[camp knife]

What should be the blade thickness right above the edge?
Click to expand...

It essentially needs to be thick enough that it doesn't ripple. How much strength is needed depends on the type of wood being chopping and the skill and strength of the chopper. An extreme range would be 0.020 - 0.040". It is very difficult to go under 0.020" and not ripple, and it is very difficult to ripple 0.040". Knives will take longer to sharpen as you increase the edge thickness and the cutting ability will go down, so some experimentation will be in order to see which combination of properties you deem best.

-Cliff
 
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