Acoustic Sensing

[Readheads]

Lots of us use USB scopes to verify max bevel contact in conjunction with a Sharpie. The scope takes time to see the full blade on both sides for a visual decision to move on.

I propose trying an acoustic pickup to some sort of computer graphics which I think will show different profile signatures as max bevel contact is approached. I envision the computer can then beep when you have reached max bevel contact as you move along the full knife edge. If it’s true that I think I can feel it and hear it, then an acoustic sensor should be able to also.

WDYT ?

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Marc H

[Organic]

I think the idea is interesting and would probably be possible, but I’m not sure if it would actually be more accurate or constitute a time savings over the sharpie / magnifier method.

Are you thinking that amplitude of the signal will be the way you determine the angle of maximum contact? One potential problem I anticipate is the need for a very low noise floor in the sharpening environment if your sensor is a microphone. You cold avoid that by using a piezoelectric sensor instead.  You’d probably need a way of plotting signal volume v. sharpening angle in order to identify the maximum because the absolute volume produced by each knife would be different. Do you think it would be sensitive enough to measure the differences between 0.1 degree angle settings?

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Marc H

[Marc H]

Wouldn’t the sound produced by each grit used, on the same knife and the same angle differ, also?  Would you need a standardized or control sound signature record to compare against?  Wouldn’t this signature differ even with the same knife and the same angle if clamped slightly differently, each time.  It think the steel would resonate differently depending on how it’s clamped.  Seems there would be a lot of variables.  Not a very cut and dry theory to try to put to practice.

Marc
(MarcH's Rack-Its)

[tcmeyer]

I’m imagining a piezo device with a feeler that you slide along an edge. Disturbances produce a noise – perhaps audio, which would alert you of a need to inspect further or to continue sharpening.  Dents and dings would produce a distinct “pow!” Not what Readheads is looking for, but maybe more practical ???

[wickededge]

Sounds fascinating!

-Clay

[Readheads]

I’m not sure what’s possible. Determining when you reach the full apex and raise a burr is probably not feasible. IMO, nothing beats the finger swipe. I was thinking that the “noise plot” would level out when say a 400 grit has removed all the 200 grit scratches. You could then minimize the strokes and metal removal. I downloaded some sound analysis software, named Audacity, and the forum talks to the non-triviality of the measurement of sound. Yet I figure the “scratch noise” is predominant to other residual noise and may be ripe for some interesting experimentation.

I will be looking at this more in the short term after I finish retrofitting my 1×30 Harbor Freight with a variable speed treadmill motor.

Also, for some reason I am not getting email notifications on replies (box is checked).

• This reply was modified 5 years, 2 months ago by Readheads.

[tcmeyer]

Earlier today, (Tuesday) I was sharpening a batch of blades from my DeWalt power planer.  They’re about 12.5″ long and beveled on one side at about 39 degrees.  I made a fixture to hold them at the right angle and did the main grind at 60 grit on my belt sander.  I sharpened them at 41 degrees on my
Gen 1 WE.  One of the blades had a more than a few dings on the edge, so I tried sliding a piece of plastic shim stock along the edge.  For sure it makes a lot of noise, depending on the roughness of the edge.

[Author]

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