Tanto forged from SR-71 Blackbird airframe titanium

Mecha

Mecha

Titanium Bladesmith
Knifemaker / Craftsman / Service Provider
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Dec 27, 2013
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A very special futuristic tanto, forged from a titanium piece of an SR-71 Blackbird, with a fancy traditional mount. This alloy responded better to heat treatment than I would have expected!


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I made a whole-ass YouTube video of the making of this blade. For some reason the audio track is a little off, and even the thumbnail looks scuffed. Not sure what that's all about, but enjoy!

 
Thumbnail's even worse. -.-\
 
wow, ya made my day.....loved watching that one being made....
 
AI says:

"A tanto is a traditional Japanese dagger or short sword, historically worn by samurai warriors. It typically measures between 15 to 30 cm (6 to 12 inches) in length, making it shorter than a katana or wakizashi. Originally designed for close-quarters combat, piercing armor, and precise thrusting, the tantō was used as a backup weapon, for self-defense, and in rituals such as seppuku. Its blade is usually single-edged, with a reinforced, angular tip (kissaki) and often features a flat, hira-zukuri grind without a central ridge, enhancing durability and piercing power.

Over time, the tantō evolved into a symbol of craftsmanship and status, with many examples considered works of art. While traditional tantō were primarily stabbing weapons, the term has been adopted in the West to describe modern tactical knives with a similar square or chisel-like tip, designed for strength and piercing ability—commonly used in everyday carry (EDC), survival, and military applications."
 
 
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Fixedwing said:
I was curious, so I looked up heat treating titanium... :cool:

The Rockwell hardness of titanium varies by grade:
Click to expand...


The various alloys with titanium as the base metal differ from each other greatly, just as with iron alloys (steel, basically), copper alloys (brass, bronze), aluminum, etc.

The characteristics of titanium are typically controlled through adjusting alloying elements, with heat treatment not for hardening; it's for strengthening, grain refinement, stress relief, etc.

For the mechanical characteristics of titanium alloys, a Rockwell hardness test isn't very useful at all for determining, predicting or even confirming uniformity in a batch. Those hardness numbers above just happen to be what they are due to chemistry; they aren't heat treated to reach those numbers or increase them at all. Most 6al4v is more like HRC 36, but it can easily vary + or - 5 points.

The heat treatment methods I came up with and refined do result in significantly harder titanium than normal as a matter of course, just due to the nature of a blade, but the goal is extreme thin edge stability under shock forces, not a hardness test number.
 
Mecha said:
This alloy responded better to heat treatment than I would have expected!
Click to expand...

Turns out there's a reason for that. Several alloys of titanium were used to make the SR-71 Blackbird, including ASTM Grades 5 ad 6, which are the OG "grades" of titanium alloy. Another alloy used on parts such as wing skins is Ti 13V-11Cr-3Al, which doesn't have an ASTM grade and is a Beta alloy.

I originally assumed this piece was Grade 6, an Alpha alloy using of 5% Aluminum and 2.5% Tin, which shouldn't have responded to heat treatment at all, but as quoted above, I was surprised to see some "hardening" effect in this blade. Grade 6, which is what's made into most of the rings, is meant to remain stable even when subjected to lots of heat and energy cycles.

Sgt. Freeman said he suspected it could be Grade 5, so a piece was sent out for analysis:

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He was correct! As a balanced Alpha-Beta alloy, the thin blade would respond somewhat to a Mecha titanium heat treatment. Furthermore, although the alloy falls within acceptable ranges for Grade 5, this very old alloy is relatively low on Aluminum and high in Vanadium, which would slightly increase the "hardening" effect even more.

Mystery solved!

EDIT: By the way, those photos are electron microscope images of the sample, which was a part of the tip that was cut off to make it more angular. The straight lines are from grinding on a 120-grit belt.
 
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