Laser device for edge angle determination

[Herman Trivilino]

Herman, did not polish the Victorinox knife until now, because it is still with the factory grind, untouched by Tormek wheels and my primary interest now is to measure the edge angle of the cutting edge.

According to "Cook's Country", the television show that recommended the knife to me, the bevel angle is 15°. That is the angle I grind mine at, and I've come to find that show to be a valid source of information.

If the bevel comes polished to a mirror finish from the factory, that might be the only way you could use your device to measure the bevel angle.

[Jan]

Herman, Ken, I agree with all what you say about polishing and honing. 

Before I started to measure my Victorinox knife I experimented with utility blades because they are flat and have pronounced primary and secondary bevels. Since their surfaces were not of mirror quality I honed them on the leather honing wheel using the standard Tormek honing compound.

To my surprise the laser image after the honing changed in a way I did not expect. The freehand honing process radiused the tip of the cutting edge and smoothed the intersection between the primary and secondary bevels. The originally symmetrical reflection image changed to an asymmetrical one. 

This experience prevents me to touch the factory grounded Victorinox knife before I finish my edge angle measurements. My accent is on non-destructive angle estimation.

Experimenting with the homemade laser goniometer is useful but also funny matter. If you have a possibility to build a similar setup at home or in the lab, do not hesitate to do it.  Children/grandchildren or students may be involved in this interesting exercise in optical imaging. 

If there is an interest by other forum members I can prepare some cartoons showing how the laser rays behave when they meet the edge. Let me know.

Jan

[Jan]

According to "Cook's Country", the television show that recommended the knife to me, the bevel angle is 15°. That is the angle I grind mine at, and I've come to find that show to be a valid source of information.

I also think the source is reliable. The more I am surprised by the fact that I have estimated the size of the Victorinox knife cutting edge angle's to only circa 20^o (bevel angle 10^o). Even more the knife was moderately used for three months. 

If the bevel comes polished to a mirror finish from the factory, that might be the only way you could use your device to measure the bevel angle.

My last photo (Reply #13) shows that laser reflections from ground surfaces can be observed also. My explanation is that part of the surface marks produced by the abrasive process have some preference orientation which causes that the laser beam is not scattered randomly. It is clear that the absence of a mirror finish weakens the reflections dramatically.   

Jan

[SharpenADullWitt]

Herman

Valve grinding compound applied to a leather honing wheel might be the answer. I have found that it is noticeably faster cutting than the Tormek honing compound. It does not leave as smooth a polish. I use it with a separate leather honing wheel. The honing wheels are easily interchanged in only a few seconds. With two Tormeks, adding the fourth step would add almost no time.

Ken

Apologies for the semi thread jack....

I don't remember if you posted a comparison of the Tormek compound, the Dursol compound, and the valve grinding compound.
Wondering what you find preference, for what?  (example, toothy knives for tomato's, use the valve grinding compound)

Thanks

[Ken S]

Excellent question, and worthy of some testing, SADW.

Just off the top of my head, based on limited experience, the Tormek compound does a very good all around job. It leaves a very polished surface. Among the reasons I generally use it is that I have accumulated several tubes of it over the years.

Dursol has a stronger ammonia smell. It works as honing compound and seems to work very well as a polisher/cleaner.

Valve grinding compound cuts more aggressively. It works nicely to remove surface oxidation. Like the others, it becomes finer with use. It does not leave as highly polished a surface as the Tormek compound.

I have not tested it for more edge tooth, although that thought has occured to me. I also think it might prove to be a useful extra grit between the SG graded fine and the leather honing wheel with Tormek compound. Switching leather honing wheels is very quick.

I need to do more testing with this; it seems promising to me.

Ken

[Jan]

According to "Cook's Country", the television show that recommended the knife to me, the bevel angle is 15°. That is the angle I grind mine at, and I've come to find that show to be a valid source of information.

Herman, I have found Victorinox recommendations for knife blades re-grinding. They recommend an edge angle between 30 and 40 degrees depending on knife usage.

https://assets.victorinox.com/medias/servive-cut-drinding-sharpening-en-nov2012.pdf?context=bWFzdGVyfGN1dHwxNzIyNzd8YXBwbGljYXRpb24vcGRmfGg1MC9oZWUvODc5ODIzOTM1OTAwNi5wZGZ8ZGJmOGVkMGRlODEzMGExYTY3Mjc4Y2U0ZmI3NmIwMzAwZjEwZmM1MzIzOWFmYjhjYzE3NTE0NTU0YTk3ZWRlNw

Jan

[Herman Trivilino]

Interesting, Jan. Thanks for posting. Note that the Victorinox kitchen knives that I've seen have parallel sides, so there is no concern about edge thickness. In other words, the angle of the blade is 0°.

The knife I have is a large slicing knife, not a boning knife, so the angle of the edge should be 30°. This is consistent with the Cook's Country claim that the bevel angle is 15°.

[Jan]

Yes Herman, it is consistent with the Cook's Country claim that the bevel angle is 15°. 

I am wondering if it is a general rule for all Victorinox professional and kitchen knives.

I have still not found an explanation for my laser goniometer measurements shown in reply #13 which resulted in an angle of the blade circa 3 degrees and some 19 to 20 degrees for edge angle. The latter seems to me unrealistically small and so I am looking for an alternative explanation of the measured reflection line (e.g. speckle effect).   

My Victorinox knife (6.8003.15) is 15 cm (6") long with max. spine thickness 1.5 mm.

Jan

[Herman Trivilino]

I suggest you use a Tormek and grind an edge angle of 30° (using the Angle Master to measure) on something, say an old knife or even a piece of flat stock, and see what your goniometer reads.

[Jan]

In the image below you can see laser lines reflected on a knife blade ground to an edge angle of 30°. The USB setup was done using the Dutchman/kenjig approach to avoid the effect of the slightly tapered blade.



Image interpretation:
A and A' are reflections from the cutting edge. The calculated edge angle is 29.8°.
C and C' reflections from the sides of the blade. The calculated angle of the blade is 3.4°.
X blade projection

This shows that the laser goniometer readings and following angle calculations are OK. 

Jan

[Jan]

Interesting, Jan. Thanks for posting. Note that the Victorinox kitchen knives that I've seen have parallel sides, so there is no concern about edge thickness. In other words, the angle of the blade is 0°.

Herman, my Victorinox knife does not have parallel sides. It is V grind. It is well visible when inserted between the jaws of a slide bar. The angle of the blade is circa 3°.



Jan

[Herman Trivilino]

Herman, my Victorinox knife does not have parallel sides.

You're right, I hadn't noticed that before, but so is mine. I have the Victorinox Fibrox Straight Edge Chef's Knife, 8-Inch.

I found this statement on the Victorinox web site:

HOW DO I RESHARPEN A VICTORINOX KITCHEN KNIFE?
The kind of edge applied to a blade, determines the sharpness and durability of it. When using a sharpening steel, the angle should be between 30-40°.

I've left a message for their support team asking what the edge angle is set to at the factory. Perhaps it's hollow ground.

[Ken S]

This topic brings up my problem with using the Anglemaster with knives. With a chisel or plane  blade, the flattened back presents a large flat surface for the Anglemaster to easily and dependably register. Knife sharpeners do not have this luxury. Knife bevels are tiny, and the larger part of the knife is rarely parallel.

I have created a work around by substituting a flat target. I made up a flat piece of metal which protrudes 139mm from the universal support in the knife jig. It should be 2.5mm thick to match the ideal jig thickness and have a bevel ground on the underside.

Using a substitute target in this manner greatly increases the efficiency of the Anglemaster with knives. I use it for the occasional knife which will not fit well with the kenjig.

Ken

[Herman Trivilino]

Victorinox has confirmed that the bevel angle is indeed 15°. Thus the edge angle is 30°.

[Jan]

This topic brings up my problem with using the Anglemaster with knives. With a chisel or plane  blade, the flattened back presents a large flat surface for the Anglemaster to easily and dependably register. Knife sharpeners do not have this luxury. Knife bevels are tiny, and the larger part of the knife is rarely parallel.

Ken

Ken, you are correct! 

Tiny knife bevel makes the use of the Anglemaster impossible because the length of the bevel is too short for proper angle setter alignment. When the sides of the blade are parallel we can align the angle setter to the knife blade. But when the sides of the blade are not parallel, the blade is V grind, than the angle setter cannot be set to the desired bevel angle. We have to correct the setting with respect to the angle of the blade.

Ignoring the blade V grind results in enlarging the edge angle by the angle of the blade. In the case of the Victorinox knife's the angle of the blade is circa 3° and so ignoring the blade tapering we will ground and edge angle of 33° instead of 30°.

Using the geometrical Dutchman's approach which is incorporated into the Kenjig concept we can easily avoid all Anlgemaster problems with knives. 

Jan