Lansky angles shallow?

L

LonD

Joined
Mar 23, 2006
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I have been sharpening with a Lansky for quite some time and have been disappointed with some of the results, namely edge durability. Getting a nasty sharp edge has never been a problem but the durability of the edges just didn’t seem right for the angle I was setting. On a whim I decided to verify the Lansky’s slot angles with a protractor. Low and behold I found that measuring the clamp alone was shallower by about 2-3 degrees than is marked on the slots. This got me to thinking that if the angles are shallow just to the end of the clamp how shallow are they when the width of a blade is added.

The Lansky is a triangle system and a little triangle math tells us that as you extend the length of one side of a triangle the angles are reduced on that side. My math skills are pretty rusty but I did the measurements of the height of the slots and the length of the base when a blade is clamped in and the math showed that adding a 1-1/4” blade will yield the following angles on the edge:

17 degree slot = 10.9 degrees
20 degree slot = 14.4 degrees
25 degree slot = 17.8 degrees
30 degree slot = 21 degrees

Has anybody else done the math on the angles created on their Lansky system on various blade widths?
If my math is hosed I’d appreciate somebody setting me straight. I’m not blasting the Lansky as it works pretty well in maintaining constant angles. However, if my measurements and math are right it would sure help explain why edges aren’t holding up quite as expected because the angle was significantly less than I thought it was.

I’d appreciate it if one of you more mathematically inclined folks would grab your Lansky, do a little measuring and calculating, and let me know if I’m off my rocker.

LON
 
You are probably getting wire edges, as edge retention is usually better the thinner you go with your angles, assuming the steel can take it. When you get wickedly sharp edges that go away extremely quickly it is usually a wire edge. You might try a couple extremely light passes at the next higher angle setting to remove the burr, or wire edge, and your edge retention should improve dramatically.
 
Angles given by Lansky don't seem to take the thickness and width of the blade into account.

When you measure the angle from the "hole" to the "tip" of the lansky device, you get approximately the angle mentionned near the hole.

I am glad with that : I prefer a smaller angle, I am almost stitched to the Lansky 20° for all my knives, that gives a full real angle of 30-35°.

Regards
 
On my Gatco system, assuming that the edge of the blade is approximately 1/2" away from the distal end of the clamp, the 11 degree slot gives an angle of 15.5 degrees. So the Gatco is approximately accurate if the edge is 2.4 inches away from the end of the clamp.

Therefore most knives I sharpen on my clamp system are sharpened at a more obtuse angle than I desire.

I find that this clamp system doesn't work very well at all with smaller blades.

What do most of you use for smaller blades? Sharpmaker? Bench stone?

I've been freehanding my smaller blades, but I wish I could jig them once in a while to get them in the ballpark.

Rus
 
Funny, maybe I'm not understanding this correctly. I remember when I first got my Sharpmaker, I checked the angle of the Lansky against it. I put my Crossbill in the Lansky and set the guide rod at 17˚. When I held it up against the Sharpmaker, it matched perfectly with the Sharpmaker rods when in the 40˚ setting. Of course mine was an extremely rudimentary experiment, so your findings are interesting.

Edited to add.
After writing this, I clamped my Yojimbo in the Lansky and did the same test. With the Yojimbo the angle of the Lansky Matched almost perfectly with the angle on the Sharpmaker. Of note is that the blade of the Yojimbo is about a quarter-inch wider than that of the Crossbill.
 
I know this is an old thread but I though I had something useful to to add to this. I always realized depending on the size of a blade, you would not get the exact angle the clamp reads. So I finally got an angle cube and checked the angles on my Lansky, with the cutting edge of my knife roughly one 1/2 inch from the clamp jaws I got the following. I am labeling these Lansky° for what is on the clamp, and actual° for what I got. I did not measure the 17° slot on the clamp.

Lansky°30/ Actual°26
Lansky°25/Actual°21
Lansky°20/Actual°16
 
I know this is an old thread but I though I had something useful to to add to this. I always realized depending on the size of a blade, you would not get the exact angle the clamp reads. So I finally got an angle cube and checked the angles on my Lansky, with the cutting edge of my knife roughly one 1/2 inch from the clamp jaws I got the following. I am labeling these Lansky° for what is on the clamp, and actual° for what I got. I did not measure the 17° slot on the clamp.

Lansky°30/ Actual°26
Lansky°25/Actual°21
Lansky°20/Actual°16
 
The 'set' angles on Lansky's clamps are valid only as measured directly at the front edge of the clamp (I measured/calculated for mine). So, any blade edge that is positioned further away from the clamp's front edge will definitely sharpen up at a more acute angle than stated on the clamp. Very wide blades will be much more acute, by several degrees. I frequently use & sharpen more 'traditional-sized' folder blades with mine, and recently figured out that positioning the blade edge ~3/8" or so beyond the clamp's front edge will produce an edge angle at around ~ 14-15°/side, when using the '17' setting on the clamp for the guide rod. Specifically, this approximates the results I got when sharpening the main spear blade on a Victorinox SAK.


David
 
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