Thicker Behind the Edge = Better For Push Cutting?

[redsquid2]

I make knive by stock removal. For whatever reason, I am ending up with my blades being thicker behind the edge within about 1" of the plunge line, and then thinner behind the edge as I go out to the tip. This isn't intentional, but it just turns out that way. I don't fuss about making the thickness perfectly uniform from plunge to tip. I think the extra thickness I have near the plunge makes sense, because that part is where I will do push cutting (which turns out to be whittling in my case). So I leave that extra thickness there.

Does this make sense to you? Of course I have more field testing to do, but I just want to know what other people think.

Thanks.

 

[FortyTwoBlades]

Sounds like you're perhaps putting a slight distal taper grind on the blades? There are merits to that, if so.

 

[redsquid2]

Well I guess a distal taper would impart more flex at the tip. I am not really aiming for that. It's just that as I start to set my secondary bevel (cutting bevel), I have a slightly thicker edge close to the plunge. Don't know if I am describing it clearly.

 

[FortyTwoBlades]

You can look at a distal taper in two ways, depending on how you're applying it--either it can impart flexibility to the tip, OR it can add lateral rigidity to a blade. Think of it as building the base of the blade up rather than taking it away from the tip. The latter may be more mechanically correct, but the former typically describes the intention of the taper from a design standpoint. It allows a thinner blade geometry without becoming overly flexible.

Generally wood carving edge angles are pretty low, but leaving more material behind the edge reduces the susceptibility of the edge from rolling when torquing the knife to break from a cut. This is why many wood carving knives are narrow zero grinds. It allows the thickest geometry for the low edge angle but keeps the blade narrow for making tight turns in resistant material.

 

[AF]

Could be because it's more difficult to grind by the plunge. Perhaps spend more time making sure the bevels are flat close to the plunge.
To me it makes more sense to have a little more edge thickness by the tip.

 

[Jason B.]

When talking about push cutting or any cutting the thinnest primary grind will always do best. Cutting performance is all about reducing wedging and stress at the edge apex and this is best accomplished by a thin primary grind. By having a thin and equal primary grind you allow the blade to pass through the material with less wedging on the sides of the blade. The thin grind also reduces the stress at the edge apex allowing it to last longer.

 

[bucketstove]

I make knive by stock removal. For whatever reason, I am ending up with my blades being thicker behind the edge within about 1" of the plunge line, and then thinner behind the edge as I go out to the tip. This isn't intentional, but it just turns out that way. I don't fuss about making the thickness perfectly uniform from plunge to tip. I think the extra thickness I have near the plunge makes sense, because that part is where I will do push cutting (which turns out to be whittling in my case). So I leave that extra thickness there.

Does this make sense to you? Of course I have more field testing to do, but I just want to know what other people think.

Thanks.

Hi,
What size blade? How thick? How wide? How long? Difference near plunge line?

Consider this image from chiral.grolim
These are all ~3-4inch long blades, ~1inch wide,
The thinnest grind is the orange one and its 1/8 inch thick at spine (rest are thicker)
None of these are thicker at the plunge line, all the edges start from plunge line with this geometry

Thicker edge near plunge line just makes sharpening a bit annoying.

Whittling wood is not all that demanding, consider this mind exploding material Extreme Regrind , ~6DPS no damage in 50 slices into pine, hardwood flooring and plywood the edge eventually gets damaged while cutting metal (steel food can)

 

[HeavyHanded]

The only common instance where thicker behind the edge will improve performance is with a Scandi grind and being used on wood along the grain.