Problem with low angle adapter

This topic has 32 replies, 7 voices, and was last updated 04/23/2014 at 4:11 pm by Josh.

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04/16/2014 at 3:18 am #18276
Gerald Welsby
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Not sure if this is the best place to put this, but as I AM getting started…
Being unable to get a low enough angle on my Japanese paring knives I acquired a low angle adapter. It arrived just as I was setting off to visit friends with my WE. I put the adapter in my pocket and set off. When I got home my wife had binned the instructions but it looked pretty self-evident to me.
I wanted to put a 12 degree (24 inclusive) bevel on one knife and a 13 degree bevel with 15 degree micro bevel on the other. I started with the 13 degree. The bottom screw was proud at that angle so it was off to the Dremel. Now here’s the problem. When I got to the stage of raising a burr there was nothing when sharpening the left side of the blade. I would do 5 passes on the left, with no result, when 2 gentle passes on the right would raise a significant burr. Also I was removing more metal from the tip of the left side than the right. I persevered and got a really sharp edge, then moved on to the next knife. I noticed immediately that I was again removing more metal from the left side. I tried measuring the angle of the blade to the vertical. It was difficult as the blade is so narrow, but it seemed to be canted 1.5 to 2 degrees to the left. I replaced the knife with a big chef’s knife and found it again canted 1.2 degrees to the left. I assume that this explains the burr problem above. What am I doing wrong?
TIA,
Gerald.
04/16/2014 at 8:06 am #18280
Richard Jackson
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We’ll I’m a newbie but I may have the answer. Most kitchen knives are full flat ground (FFG) which means the primary bevel is a constant angle that extends from the spine to the edge. So you basically have a very acute V shaped piece of metal between two jaws that are more or less parallel. This will allow the blade to cant to one side or the other unless you have absolutely mastered keeping it centered. Most people use a piece of leather or chamois or foam between the blade and the jaws on FFG blades to give it some more support below the spine to ward off the cant.

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04/16/2014 at 9:04 pm #18286
Gerald Welsby
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Richard,
thanks for that. It sounds like an explanation. As an experiment I applied a clockwise torque to the knife while tightening the vice. It did ameliorate but not solve the problem.
Can someone with a low angle adapter please let me have the instructions for its use? I just dropped it into the main vice and tightened. I measured some angles today. My riser is inclined at 0.3 degrees to the left. The non-moving vertical part of the adapter is angled at 1.0-1.1 degrees to the left. Are these normal/within spec?
TIA,
Gerald.
04/16/2014 at 9:39 pm #18287
Richard Jackson
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What are you measuring angles with and where? Are you measuring on the inside of the low angle adapter vice? Just FYI, the main vice will have exactly the same issue you described in your first post(the cant) if you don’t use the leather, foam, or chamois with a FFG blade.
04/17/2014 at 12:58 am #18295
Gerald Welsby
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Thanks again Richard. I am using the angle measurer which comes with the Pro 2 kit. I put it on the flat top of the riser to get the .30 degrees. You are entirely right – I tried the main vice with a big Tojiro Senkou chef’s knife (no chamois) and got the same result. The knife is not exactly as you describe. It tapers from the shoulder down to the bevel which then is more obtuse at 12.5 degrees but this latter would not make any difference as it’s not touched by the vice. I’ve tried with and without chamois but it’s the same either way. Is there a technique for getting the knife perfectly vertical?
Thanks again for your help – much appreciated.
04/17/2014 at 4:39 am #18297
Josh
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Are you using an angle cube?

Josh
04/17/2014 at 8:33 am #18300
Gerald Welsby
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Josh,
yes, that’s the name I was looking for!
Gerald.
04/17/2014 at 4:22 pm #18304
Josh
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Can you post pictures of the knife? I’m wondering if the primary grind has any effect here

Josh
04/18/2014 at 4:42 am #18313
Gerald Welsby
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Josh,
when I looked at the Japanese chef’s knife I saw that the primary grind was not symmetrical. However, I tried again with a simple Victorinox chef’s knife which has nothing strange about it. Here are the photos. Note that on both sides of the blade the Angle Cube is showing inclination to the left.
G.
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04/18/2014 at 5:10 am #18314
Gerald Welsby
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Josh,
so doing the maths it looks like:
Angle of cant plus angle of taper of blade shoulder to edge = 2.1 degrees
Angle of cant minus angle of taper = 0.5 degrees
Angle of cant = 1.3 degrees
Angle of taper = 0.8 degrees.

Any explanation?
TIA,
Gerald.
04/18/2014 at 5:20 am #18315
wickededge
Keymaster
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Gerald,

It could be your angle cube. Try rotating the cube 180 degrees on its vertical axis when you switch stones. You’ll have to peek around to the back to check the angle after you switch to the other side. Explained another way, you would have the display of the angle cube facing you when it’s on the stone on the right hand side and facing away from you when it’s on the stone on the left hand side. On some angle cubes that has been an issue that was observed by Bob Nash from Oldawan.

–Clay

-Clay
04/18/2014 at 5:42 am #18317
Eamon Mc Gowan
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Clay,
How in the world do ever remember all this stuff? :S It’s a good thing a smart guy is running the company! :cheer:
04/18/2014 at 5:56 am #18318
Richard Jackson
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If you take the moving jaw off and put the cube on the stationary jaw between the top vice screw hole and the bottom vice screw hole what do you read? Please take a picture of where you zero it and the reading on the stationary jaw.
04/18/2014 at 6:29 am #18319
Gerald Welsby
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Clay,
thanks for the reply but that’s not it. I get the principle – the cube is always leaning to its left so it removes any difference when it leans to its right. Right here I’m not trying to measure the angle of the stones but checking the verticality of the blade in the vice. I’m measuring (in this case) a lean of 2.1 degrees to the left when the cube is on the right side of the blade as I look at it, leaning to its left. On the left side of the blade it’s leaning 0.5 degrees to the left. If I flip it 180 degrees it reads 0.6 degrees. So the knife is inclined 1.3 degrees from the vertical in the vice. That means that when the cube is showing 12 degrees on either side on the stones I’m really getting 13.3 and 10.7 degrees. Can I just accept that the blade is tilted and add/subtract 1.3 degrees to/from the right and left sides or is the geometry more complex than that?
Regards,
Gerald.
04/18/2014 at 6:46 am #18322
Gerald Welsby
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Richard,
see the attached. The cube is zeroed on the granite plate. It reads 0.35-0.40 on the static jaw. Using the granite as a surface plate the moveable jaw is flat apart from the metal opposing the bottom screw.
Gerald.

Btw guys, thanks for all your help but it’s 3.50am here so I’m calling it a night!
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- photo4.jpg
- photo5.jpg
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