Too frequently one sees the advice "Make sure it is a full tang knife". Obviously, over the years enough hidden tang knives have broken to cause some concern. But really, there are several different ways of constructing hidden tang knives some of which are just as sound (if not more so) than a full tang.
Hidden, stick tang knives that are assembled via tension alone are probably the source of the problem: With a threaded pommel or rivet compressing the handle materials, strength comes form the rigidity of those materials under compression alone. If the handles shrink at all, that tension is lost and now the skinny stick tang is doing all the work. On top of that, if there is no glue or epoxy used, moisture will eventually get at the tang and corrode it. Not so good.
On the other hand, of the knives I've seen with broken tangs, many of them were full tang knives. They broke at the top rivet hole, despite sporting synthetic handles. Again, corrosion was probably a factor - epoxies tend to like to stick to synthetics and wood more than metal, so if the rivet loosens or the scales change shape, the protective glue is going to go with them, leaving the metal exposed. Aside from that, is a hole really what you want drilled in the tang up so close to the bolster?
I think that possibly the most durability probably comes from a hidden tang knife that is a good percentage of the blade's width up near the bolster (it can taper after that) and is epoxied into a blind hole in the handle materials. If done correctly, this gives you the best protection from hidden corrosion, since the tang is only exposed as it passes through the bolster, and the blade is completely surrounded by the material it is epoxied to, which gives the handle no direction to pull away from the tang. We might call this a hidden V-tang.
Hidden tang stronger than a full tang. Kind of a bold statement. But when you consider the more complete bond, continuous handle material, lack of corrosion exposure and lack of stress-rising tang holes, it starts sounding not so unlikely.
The Proposed Test:
Two dummy blades are constructed and heat treated of the same steel stock. To mimimize comparison problems of variable heat treating, the tang portions would be fully hardened. The handle shape would be a basic rectangle of the same exterior dimensions, using the same grade micarta (a material that is both very strong and bonds well with epoxy and resins).
The full tang version would have 3 rivet holes. Additionally, it could have the usual hollow area to promote increased bonding between the scales and minimize weight.
The V-tang knife would start out relieved 1/8" from the spine and edge and then taper from there. Micarta would be built around it, either in a 3 layer sandwich or in-line with a bolster and handle piece. Epoxy would provide 100% of the bonds. Then, the two handles are tested for strength.
Here's where it gets tricky. How thick is the steel? Would a thicker tang better expose the weekness in the handle material, or would a thinner, flexier tang make the handle work harder? How do we test? Bending, twisting, impact? It has to be something that actually causes a failure of either handle or tang, but not the blade itself.
This isn't an attack on full tang knife construction - far from it! At most it is a harsh criticism of non-glued construction. But it is also a call for some common sense when it comes to evaluating the potential strength of a knife. For instance, I would rate a hollow handle survival knife like this Martin:
http://www.jerzeedevil.com/forums/showthread.php?t=42461...as probably being a better bet than a full tang knife with wood handles and rivets. Newt has never had a handle failure bonding steel to aluminum!
FYI - Randall has some knives that split the difference by surrounding the tang on 3 sides. Not a bad compromise.
So I'd like to hear your thoughts on construction/destruction test that puts these things in perspective. I do prefer hidden tangs for the knives I build, but only because of the reasons I've stated (and the fact that you get to see more lovely wood). Thanks.
-Andrew
Hidden, stick tang knives that are assembled via tension alone are probably the source of the problem: With a threaded pommel or rivet compressing the handle materials, strength comes form the rigidity of those materials under compression alone. If the handles shrink at all, that tension is lost and now the skinny stick tang is doing all the work. On top of that, if there is no glue or epoxy used, moisture will eventually get at the tang and corrode it. Not so good.
On the other hand, of the knives I've seen with broken tangs, many of them were full tang knives. They broke at the top rivet hole, despite sporting synthetic handles. Again, corrosion was probably a factor - epoxies tend to like to stick to synthetics and wood more than metal, so if the rivet loosens or the scales change shape, the protective glue is going to go with them, leaving the metal exposed. Aside from that, is a hole really what you want drilled in the tang up so close to the bolster?
I think that possibly the most durability probably comes from a hidden tang knife that is a good percentage of the blade's width up near the bolster (it can taper after that) and is epoxied into a blind hole in the handle materials. If done correctly, this gives you the best protection from hidden corrosion, since the tang is only exposed as it passes through the bolster, and the blade is completely surrounded by the material it is epoxied to, which gives the handle no direction to pull away from the tang. We might call this a hidden V-tang.
Hidden tang stronger than a full tang. Kind of a bold statement. But when you consider the more complete bond, continuous handle material, lack of corrosion exposure and lack of stress-rising tang holes, it starts sounding not so unlikely.
The Proposed Test:
Two dummy blades are constructed and heat treated of the same steel stock. To mimimize comparison problems of variable heat treating, the tang portions would be fully hardened. The handle shape would be a basic rectangle of the same exterior dimensions, using the same grade micarta (a material that is both very strong and bonds well with epoxy and resins).
The full tang version would have 3 rivet holes. Additionally, it could have the usual hollow area to promote increased bonding between the scales and minimize weight.
The V-tang knife would start out relieved 1/8" from the spine and edge and then taper from there. Micarta would be built around it, either in a 3 layer sandwich or in-line with a bolster and handle piece. Epoxy would provide 100% of the bonds. Then, the two handles are tested for strength.
Here's where it gets tricky. How thick is the steel? Would a thicker tang better expose the weekness in the handle material, or would a thinner, flexier tang make the handle work harder? How do we test? Bending, twisting, impact? It has to be something that actually causes a failure of either handle or tang, but not the blade itself.
This isn't an attack on full tang knife construction - far from it! At most it is a harsh criticism of non-glued construction. But it is also a call for some common sense when it comes to evaluating the potential strength of a knife. For instance, I would rate a hollow handle survival knife like this Martin:
http://www.jerzeedevil.com/forums/showthread.php?t=42461...as probably being a better bet than a full tang knife with wood handles and rivets. Newt has never had a handle failure bonding steel to aluminum!
FYI - Randall has some knives that split the difference by surrounding the tang on 3 sides. Not a bad compromise.
So I'd like to hear your thoughts on construction/destruction test that puts these things in perspective. I do prefer hidden tangs for the knives I build, but only because of the reasons I've stated (and the fact that you get to see more lovely wood). Thanks.
-Andrew
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