Blade Angle Finder

[Rupert Lucius]

Jan's angle tester got me interested in blade angle testing -

From You Tube comes this: https://www.youtube.com/watch?v=3ICnxj6TDjs

Rupert

[grepper]

Well, Mr. Rupert, that seems very cool!  Can it really be that simple?

I would imagine that getting the blade exactly perpendicular to the laser and general setup is critical for precise measurement.  

I’m trying to imagine how a hollow grind would reflect.  That doesn’t look like a very focused beam.  It would be interesting to see what would happen with a super tight beam.

What if you rotated the light so that the reflection remained vertical as it moved over the edge?  Could you read the number of degrees that the light was rotated?

It will be interesting to hear other people’s comments.

Thanks for posting that!

[Jan]

Mr. Rupert, thanks for posting the link to a very interesting video. It is really good food for thoughts.
It uses the same physical principle – the law of reflection – as my laser goniometer.

           

Laser goniometer is not my invention, it is used in Catra instruments and was also described by US steel expert prof. Verhoeven. His paper inspired me.

As mentioned by Mr. Grepper, the you tube design may require more precise geometrical setup to estimate the bevel angle correctly. But on the other hand it has some advantageous also. Definitively inspiring for me.

When the reflection takes place on a hollow or convex grind, than the reflected laser line is not a single line, but a bunch of lines. The width of this bunch is given by the curvature of the grind.

 
   

[Rupert Lucius]

My thoughts are that,

Grepper and other UBS camera/microscope owners are able to measure blade angles?

Wish I could lend more to these subjects, I will lurk, be prepared and ready to replicate.

The ability to measure angles?  Hard numbers from sharpness testers (EdgeOnUp) let's say WOW!

Rupert

[grepper]

I know that Grepper is not able to measure blade angles with his USB microscope.

[Rupert Lucius]

There must be someone out there that will help us with measuring blade angles.

[Jan]

My friend, excellent Slovak sharpener Pavol Sandor, published on you tube a series of contributions "Knife blade profile measurement" Part 1 to 4. It is commented in Slovak language only, but it is well understandable also without the comments.  https://www.youtube.com/watch?v=l8hrhp4UZHY

He prepares a wax imprint of the blade, makes a digital photo and measures the angles on the screen.

His method works well, but requires a little bit of skill and time. When Pavol needed to measure the bevel angles* of a DE razor blade, he asked me to do it with a laser goniometer.


*P.S.: The results obtained for ASTRA Superior DE blade were: first bevel angle = 7°, second bevel angle = 8.5° and the included angle = 15.5°. BESS sharpness was 50 gf.

[Jan]

The simplest way how to estimate an edge angle are measuring grooves. They work if the bevel is not too short.

   

Professional tool is a Vernier protractor.

   

Catra laser goniometer enables to measure bevel angles, while the two previous tools measure only the included (edge) angle. Catra tells us if the blade was shaped symmetrically.


   

[Edgepal]

Tthis video shows with my sharpening tool Chef.

https://youtu.be/uklnV3Ch2VE

In this movie I speak Swedish - but you see what I am doing. I use the old method with a magic pen and I use permanent black color, it give a layer of ink that is 1/100 part of 1 mm thick. A white board pens ink is 2/100 part of 1 mm thick.

When I have found the angle I lock the angle and use the magic pen again to be secure. Chef have a built in protractor that allways shows the correct degrees - and I just read the degrees direct from the protractor.

Thomas

[Jan]

Mr. Thomas, thanks for mentioning your approach! In my understanding your angle measurements are quite precise and may enable to estimate the bevel angle of a very short microbevel also. This is challenging even for laser goniometer.