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Gritomatic Goniometer
#11
All of this has piqued my curiosity. I'd be interested in learning how well these work and how much, if any, the bevel polish affects the user's ability to clearly identify the bevel angle. My question is based in this: The light emitted by a diode laser is "coherent" meaning that all the photons are at the same frequency. This is what gives laser light the ability to "hang together" and resist scattering through air as normal or incoherent light does. Once that coherent light strikes a  surface though, it diffuses or scatters commensurate with the roughness of the surface. Scattered light would manifest as reflected light producing a sort of blurry edge  making it difficult, I would think, to determine the precise bevel angle. Of course highly, polished bevels would reduce this occurrence but even glass mirrors of the highest quality do not provide perfect specular reflections. A high quality glass mirror might be 90% reflective. I have no good idea what a high quality polished metal surface might provide but I would guess - perhaps 40%? 

If anyone has experience with these devices I would be interested in learning how well defined they are and how the bevel size and polish affect the ability of the user to read the results accurately
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#12
(02-12-2020, 08:57 AM)BeSharp Wrote: CATRA has their basic goniometer on sale at 79 pounds sterling:

http://www.catra.org.uk/CATRA_Hobbigoni_...p/cuhg.htm

Do not waste your money on above  Catra device, it is not anything that you would expect from our English Cousins.  I,  sold the one I had for 25.00$ many years ago.

At the least move up to the Catra that our cousin from Australia uses. May be about 700/800$ plus or minus.

Edgepal's Chef (Thomas) for sure is one of the best guided sharpeners (maybe the best).  Nothing could be more accurate for reading the blades edge angle or angles with the help of a red marking felt tip, and possibly to speed things up use angle cube.

Earlier today I made (about 10 AM) two telephone calls to Grit O Matic in Cartersville, Georgia USA and left a message with my tele number - at this time I have had no answer (now it's 2:27 PM here in Louisiana).  

About 10:30 AM sent Email on their site - stating that I wanted to purchase one of their "blade edge angle meters".  No response, none.

My tele calls may have been rerouted to somewhere in this World other than Georgia USA?  Not the service that I expected.
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#13
Ordered the Gritomatic. Will report back once I get it. Hmm, sounds like good thing I didn't get the cheap CATRA. Thanks Rupert!
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#14
Let us know -

Rupert
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#15
The Czech based company Vetako also makes two laser goniometers, the Pro and the Pro+
https://sharpeningtool.eu/en/catalog/accessories

This is a short clip of the Pro+ version: https://www.youtube.com/watch?v=6DX1NGon...e=youtu.be

A company representative recently made an account on the Dutch knife forum, maybe he's interested in sending me one for testing/reviewing purposes.
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#16
Sir -

I, am a potential player
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#17
There are many questions about messuring a blade. Are the blqde sides really parallell on a parallel blade, are a triangular blade really triangular for example. My answer is that parallel blades are surpicering often not parallel and that triangular blades surpricing often are not centered...

When there is a problem here, the problem also concern the edge becouse the problem from the sides slides over to the edge. I have never, so far, meassure a edge that have the same angle on both side of the edge.

Older blades was often stamped out with a big, heavy stamp, from sheatmetal. If the stamp did not hit the metal 100% correct, the stamped blade come out not parallell from the stamp. I found this out on old Mora blades for some decades ago. I could se how the stamp hit the blade and where the biggest power in that hit was.

Then a rotating big grinding machine grind out the edge, one machine on one side, a sexond machine on the other side. If those machines grind in different angles (and they allways did) the edge was not perfect
centered allreasy in this stadge.

of cause, i talk here about very small meassures, some hundered parts of 1 mm. For a normal knifeowner, this small things so not matter, they so not even se it or feel it. But - for understanding how edges work, this is importent understandings about how the problems are when we like to meassure our edges as exact as possible...

In my mind, we must build something that meassure one side at the time to get as exact figures as possible. The two sides meassuring is not as accurate we need to have.
One side meassuring are, in my mind, more easy to conatruct with the laser but more difficult about hiw we fix the blade to the "meassuring table". The "laser tower" that gives the height, or, yhe meassuring table, must be able to slide forward and back (the measuring table also in height up and down in a secure way so that it is possible to meassure blade sides in exactly the same height (all blades have not the same thicknes). Perhaps can we adjust the laser height instead of the meassuring table?

All tye meaasuring devices I have seen meassuring a free hold kniveblade and the edge cut the laser beam and show the result on both sides of the edge with red dots on a double "protractor". To get the dots correct on both sides they adjust the red dots by turn the blade a little - so the red dots shows the result after a man made adjusting of the angles.

That is why we need a tool where the blade are fixed in position on a "meassuring table" where the blade cannot move during the meassuring.

In my mind this tool must allways use the same distance between the cutting edge and the laser head. Thats why the rool need a sliding part. Then it is possible to meaasure a small blade and a cleever in the same tool.

Depending how we like to read the result we can construct this tool in many different ways, shall we read behind the edge as on the tools there is today, or on (or thru) the "roof" in a box?

This is just lose thoughs from my side, if someone like my way of thinking, use what I wrote and build a tool Smile

Thomas
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#18
Thank you Thomas, for your input

Rupert
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#19
Got it yesterday after paying the taxes ($12.91) and the Canadian government’s handling fee to collect said taxes ($9.95). Looks OK for the money.


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#20
(02-24-2020, 01:57 PM)BeSharp Wrote: Got it yesterday after paying the taxes ($12.91) and the Canadian government’s handling fee to collect said taxes ($9.95). Looks OK for the money.
Please keep us posted - thank you

Rupert
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