hardened area?

[Cymro]

I've been reading the safety thread every day (and will continue to do so for a month). One of the notes says (in part): "Before cutting hard targets, it is best to practice controlled striking (with the hardened area--have to determine that as well)"
How do I determine where the hardened area is?
That, and any other safety tips y'all feel like throwing my way.
Bahut Shukirya, everyone! (except Yvsa, for whom I believe the phrase is 'Wa-do'!)

 

[Steely_Gunz]

Generally, the hardened area is right where you would expect it to be, that is the spot you would chop with. usually the fist inch or two of the blade is softer than this area (but not by a HUGE amount). The sweet spot usually extends 3 or 4 inches depending on the model, then it gets softer again. To test for the hard area you can do a couple of things. the easies is to run a file down the edge. the parts that are softer will grab the file. the harder parts will skate a little more. OR you could etch the blade. this will make the harder areas POP a bit.

Best of luck
Jake

 

[ddean]

here's one thread to start:
http://www.bladeforums.com/forums/showthread.php?t=291160

for more---
search -this- forum

on thread-list page
far right button in HI Forum menu line, above thread list
"Threads in Forum: Himalayan Imports Forum Forum Tools Search this Forum"

for:

spot file
spot etch
sweet hardened
sweet hardening
hardness skate




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[Dave Rishar]

When you're chopping, listen to what your arm is telling you. The impact shouldn't jar you or torque your wrist. If you're chopping in such a way that the energy coming back up your arm is minimal, you're chopping with the sweet spot. The kamis are pretty good about putting the hardened area there.

 

[kronckew]

now for the techie stuff from an engineer:

the 'sweet spot' is the center of percussion, ie. when subjected to a vibrational energy input which forms a standing wave along the length of the object, the sweet spot is the zero amplitude longitudinal position of the wave, which remains constant thru the duration of the vibration (it don't move up & down) - the position of no vibration. like a baseball bat, there is a 'sweet spot' where maximum energy transfer occurs when hitting the ol' leather orb, and which proponents of the art find by instinct, as hit it anywhere else and you know it feels wrong. it 'burns'. any object used to hit another has a 'sweet spot' or two.

same with swords and large knives. they are designed to get the most use out of the first few inches, and the sweet spot is normally a few inches back from the tip and is where you want to hit your target. the turkish kilij is another example of this taken to it's extreme as in a kukhri

from an engineering standpoint, there is also a secondary 'sweet spot' near the hilt, but this should not be used as it is normally a high stress area as well and impact there, as in a forcefull parry will absorb all the energy rather than disipate it as intended with a parry, and may result in blade breakage.