Plunge lines - why?

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kailand09

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Mar 13, 2013
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Hello, I'm new here. Was recently showed the knife-making world. I am reading all I can about knife-making before getting started this summer...

That being said, after seeing all this, what is the point of the plunge line? I haven't found any posts really stating it here, and have read this thread :

http://forums.dfoggknives.com/index.php?showtopic=21341

Is the only reason really either style decision, or remnants from using rotary wheels a long time ago? Is there no practical use in the function of the knife, or structural reason to have it?

I can't see any particular reason thinking about it. Someone there stated it as being, oddly, harder to not have a plunged grind. Is that true? I would think it would be easier.

Any insight is extremely appreciated! Thanks
 
Well, I do not know much but I can give my opinion - It keeps the grind looking clean and uniform. I do not believe it has any function other than ending the grind You could blend the grind into the ricasso or just grind straight to the guard/ferrule/handle... Like you said, I would imagine this would be easier (though I have not attempted it myself).

I am sure someone else will have a more detailed explanation.
 
Its mostly to make it look clean and the cleaner you get the less it looks like a person touched it which is what most crafts people hope to achieve.
 
If I want a blended transition there I have to carefully create that transition and attempt to keep it even on both sides. I also have to leave room for that transition between the actually blade area and the handle material. That is not nearly as easy or quick as using a grinding jig that keeps my plunge line where I want it. In realistic terms we almost always blend them somewhat, just not to the point they're almost invisible. It's rare to see one that is actually a sharp corner. I blend most of mine with the edge of a fine belt rolled over the edge of my platen. It rounds that transition slightly while still leaving a clean and distinct change from blade to non blade.
 
Simply stated, the plunge line shows that the edge is properly centered and the grinds are crisp and clean. It does no other function.
 
Thanks for the answers. I thought this would be the case, but just felt like it could be more complicated than I was seeing.
 
Contrary to at least one of the posts on that link, plunge lines are uncommon to rare in early blades, from my research. Very rare on working knives. Subtle plunges can be seen on some early swords, and most early blades are a subtle convex grind. Some being near flat, but not quite.
 
LRB has it I think. I only use plunge lines when the design calls for it. The majority of my knives are "plungeless". From a high volume production perspective(using flat barstock), plunges can make sense. It also makes things easier for guards and bolsters. Aesthetically, it provides a pleasing transition from ricasso to bevel. If done smoothly it reduces potential stress risers at the transition.
 
bladsmth said:
Simply stated, the plunge line shows that the edge is properly centered and the grinds are crisp and clean. It does no other function.
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I must humbly correct you Stacy. It's other and I would say main purpose is to drive us crazy and make our lives miserable. :grumpy:

;)
 
Rick Marchand said:
LRB has it I think. I only use plunge lines when the design calls for it. The majority of my knives are "plungeless".
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Also, a lot of great modern kitchen knives (almost always full flat grinds) and small working knives (mostly scandi grinds, it seems) are plungeless - ie, the angles of the blade bevel continues all the way to, if not through the tang. I've only ground a few blades this way but I'll be doing more. It looks great, gives the absolute maximum amount of useable edge, and really isn't any more difficult than establishing a ricasso and plunge. I find it easier, in fact. All you have to do is keep your bevel faces flat all the way from tip to butt.

(Obviously, this would not work very well at all with hollow grinds... and I suspect the advent of factory-made hollow-ground blades would correlate strongly with the prevalence of plunges as we know them today.)

In theory, a fully axially-tapered blade and tang might seem to make it more difficult to mount scales and bolsters on full tangs, and guards on narrow tangs, but in practice I haven't found that to be the case... certainly no more difficult than doing distally-tapered tangs. If you like cord-wrapped handles, it presents no problem at all, and in fact gives a much nicer, more oval handle geometry than a flat tang.
 
james terrio said:
Also, a lot of great modern kitchen knives (almost always full flat grinds) and small working knives (mostly scandi grinds, it seems) are plungeless - ie, the angles of the blade bevel continues all the way to, if not through the tang. I've only ground a few blades this way but I'll be doing more. It looks great, gives the absolute maximum amount of useable edge, and really isn't any more difficult than establishing a ricasso and plunge. I find it easier, in fact. All you have to do is keep your bevel faces flat all the way from tip to butt.
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I started out on kitchen knives to avoid plunges. I thought it'd be easier. I was wrong, because everything else about a kitchen knife makes it as difficult as any other blade.

But I'm still hooked on kitchen knives anyways.
 
Patrice Lemée;11972603 said:
I must humbly correct you Stacy. It's other and I would say main purpose is to drive us crazy and make our lives miserable. :grumpy:

;)
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Naah, just makes for more work. Now, if you really want a reason to moan and groan, try fitting a guard to a dagger with no ricasso and a diamond cross sectioned blade, which results in a tang that is 6 sided, and get it to fit with no visible gaps. My hair is thin, but it's not from age alone.
 
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LRB said:
...try fitting a guard to a dagger with no ricasso and a diamond cross sectioned blade, which results in a tang that is 6 sided, and get it to fit with no visible gaps...
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I'll pass, thanks. Four-sided holes are plenty difficult for me :)
 
Wow lots of great response and discussion. What really makes no plunge blades tougher to bolster or guard? Shouldn't you have the same flat surface either way?
 
One example to get an idea from is the habaki. It's not a squared opening, which makes things less straight forward.

kinkise_habaki%20(2).JPG


Using a plunge, the guard slot can be rectangular which simplifies the process some. Without the plunge, the bevel will just continue.
 
kailand09 said:
Wow lots of great response and discussion. What really makes no plunge blades tougher to bolster or guard? Shouldn't you have the same flat surface either way?
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I find them about equal. As you said, a flat surface is almost required for a good fit in either case. I make early type knives with a gentle convex grind, and most often no plunge, and a blade that has a heel below the grip level. I never carry the grind above the grip level in that zone immediately forward of the grip, but grind it as a gentle blend in a 45° angle from the heel aimed forward into the spine. This ends up with a flat forward of the grip as a continuation of the flat tang, but is not noticable unless a straight edge is layed upon it, if done right. A tapered tang from the heel back takes a little more careful blending, but can be done.
 
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kailand09 said:
Wow lots of great response and discussion. What really makes no plunge blades tougher to bolster or guard? Shouldn't you have the same flat surface either way?
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They are (or should be) flat, but the two sides of the tang are not parallel to each another. You're no longer dealing with 90's and 180's, angle-wise. That means you have to plan ahead more when drilling and shaping.
 
Sometimes there called for sometimes there not called for; depends on whats being built. Many smiths build period knives without plunge grinds in them, makes seance there. Modern fighters without plunge grinds look very odd to me. Integral knives have no need of plunge grinds.
 
Don- that pictures makes TOTAL sense, thanks for that. I should have seen that, but that's life.

Thanks everyone. I had been looking around the site and came across the camp knife competition... Saw one without any plunge and almost liked it more for an all around camp knife (food slicing / wood splitting / bush whacking) . I thought with a 1084 steel I could make at least some decent knife for the application and was deciding plunge or not. This information helps!
 
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