Singing, ringing steel

J

Jim Shultz

Joined
Apr 15, 2006
Messages
17
Yo, I just hit a bunch of blades with a large nail near their tips. Most did not emit a metallic note when two-finger dangled from the handle. Does a high pitch singing or ringing steel indicate a harder or denser blade? A Swede bayonet, a 1941 Spanish bayonet and a German machete sang. Said three blades are not shaped the same. Thanks, Jim
 
hm... I don't know the answer, but I'd be interested to find out. Were they all fixed blades? Folders' blades might not be long enough to vibrate for long, or may be dampened by the pivot joint.
 
A while back I read a post where someone was using a Trace Rinaldi Annaconda hardened by Bos. They said that every time they hit it on the side that it rang like a bell and while chopping at a frozen elk bone that it also rang after each chop.
I don't know if this is a good thing or not but I know the Bos does know how to heat treat a knife blade.
Judge for yourself.

Ciao
:cool:
 
Most of them were fixed blade bayonets, 7 to 14" long. One should hold the blade near your ear and strike at several areas to try for the bell tone. A wide thick blade will ring lower than a petite one. A folder's potential dampening effect could shorten the vibration time, or affect the resonant frequency.

It's essentially a seismic study; sound or pressure waves travel faster through a denser medium I think.
 
I don't know really, but on the Spyderco forum someone posted a video that showed a knifemaker at work. According to him the tone of the blade depends very much on the tension of the handle. He was making a hidden tang with bolster. I don't know how that translates to handle slabs.
 
I haven't figured out the difference, but it can be very conspicuous. For example I have seen a lot of machetes, but none of them sing like a Legitimus Collins. The old Collins brand were made with an alloy similar to 1084. They hardened them more than a lot of other brands that I ran across. A lot of other brands are made from lower alloys closer to 1050. Other machetes are made from 1095, but I doubt that they quench them fast enough to be as hard as the old Collins. Even when they switched production to Guatamala and Colombia they still kept that special Collins ring.
 
I have an old Collins that has been like a tank. I l;ove that old thing.:thumbup:
 
All blades ring, depends alot on how the handle is set up and how it inferferes with the blade harmonically. If you took the handles off all your knives, hung them by a thin string, and hit them with a drumstick or something similar you'd hear a distinct bell or ring sound. From what I've observed harder ones seem to ring at a higher note than soft ones, volume seems larger on big blades, etc.
 
There are dramatic differences between how long blades ring that has less to do with the handles than you would expect. You can take two similar machetes with rivetted hard plastic handles, one of them a Collins and one of them which isn't. And you can take a Collins with a wooden handle. If you ring test them the two Collins will sing with a clearer note which will be sustained longer than the other machete. The blade similarities are more important than handle similarities. I don't understand why, but the harder blades seem to have a lower damping coefficient. That gives them cleaner harmonics and causes them to oscillate for a longer time. I guess that the harder alloy has a more linear stress-strain curve. Normally I expect the stress-strain curves of a couple carbon steels to look very similar until you get close to the plastic yield point of the steel. When you ring a blade I would expect you to be a long ways below the yield point and the blades to oscillate the same. I guess that that isn't true. Softer steel is yielding plastically to some small degree somewhere. That is damping the vibration and broadening the natural resonance peak.
 
I have a theory (which I just thought up) that the difference between the ringing characteristics of some alloys comes down to dynamics. If you apply force to the hard and the softer steel they will stretch the same amount up to the point where the softer steel starts to yield plastically. I believe that the yield point begins at a lower stress for rapidly applied stresses. When you measure the youngs modulus of steel you use static loads. When you tap on steel and make it ring you are applying rapid loads with repeated rapid oscillations. I would guess that this is not true for materials commonly used to make wind chimes. For example those are commonly made of glass. Likewise the bronze that is used for bells probably doesn't have this characteristic.
 
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