fp.

Hm usually ultrasonic cutting tools have small, disposable blades, which are tuned so that they vibrate right. Also they can produce an intense burning sensation in either the hand you're using (if you hold wrong / too tight) or in your off-hand (if you hit something hard, like a bone, which can pick up the vibrations).

I'm sure there's an ultrasonic transducer in there but I wonder how a 40w transducer (this is typical power for hand-held) can move such a giant blade around at 40khz. It does not seem physically plausible to me.

sheimend•2m ago

Hey there, Scott here. I'm driving the knife at actually only 10W. When in resonance, this produces a stroke amplitude of 10-20 microns (depending on the spot on the blade) which is large enough to have a measurable impact on the ease of cutting. 50% reduction in peak force for tomatoes (as measured quantitatively with a robot arm), and I've seen even higher in other foods.

At this power level, there's no heating of the blade like the small blade tools you're describing. And firmware in the handle adjusts the operating frequency continuously to stay in resonance.

This all works because the ultrasonics aren't moving the blade like a reciprocating saw -- that would indeed require huge power. They're sending longitudinal shockwaves through the blade itself that cause the metal to expand and contract. Check out minute 2:30 in the video here to see that motion in action: https://youtu.be/cXjbSVt9XNM

gurgeous•13m ago

I have used this knife, I am an angel investor in Scott's company. The thing is legit amazing. He labored for years to bring this to market and it shows.