Straight edge knife-guided sharpener questions

CelloDan

CelloDan

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Dec 2, 2017
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Hi folks :)

A couple days ago I received a budget model guided sharpener system and I have sharpened two of my lambsfoot knives with very good results.

After sharpening the first one I noticed that the middle of the knife's edge had a very slight curve inwards, as in more steel had been removed in that area.
I then recalled that the grind was very uneven to begin with from the factory, so in my head problem solved.

For the second knife I made the edge perfectly straight, from tang to tip with a file before sharpening and went at it ( checked by resting edge on a piece of wood and shining a light from behind)

As the initial major re profiling was under way I noticed the the middle was the first spot to develop a burr, so I decided to concentrate more on the area close to the tang and the tip which were noticeable thicker.

I then checked the angles of the system.

Hone straight at the middle of the knife was what I had set it - 17 degrees.
On either side the angle was 16 degrees.

So I carefully raised the angle by one degree and continued to do only the ends of the blade trying to get an even bevel.

I also realized that with my system I could move the clamp/knife left to right to align either end of the knife straight in the middle of the system and just keep the original angle ( system not intended to be used this way I am sure )

CFwgdSZl.jpg


The results were very good :thumbsup:, but not perfection . I still managed to take a very tiny bit more steel from the middle than from either side.

A lot of the vintage lambsfoot knives that have been sharpened on stones look like this.
Why ?


VazJjTi.jpg


Any tips to be able to maintain a perfect straight edge on on these knives either with guided systems (or stones )?
 
Yes, check for a warped, bent or bowed blade. It's very rare when there isn't any warp, bow or bend at all, in supposed 'straight-edge' blades like sheepfoot or Wharncliffe profiles. Even a tiny bit of warp, bow or bend will induce uneven sharpening patterns along the bevels, if sharpened on a flat stone.

Might also see it in blades with a wavy grind or uneven thickness of the blade. I have one knife where it can be clearly seen in one portion, that the belt used to grind the blade's primary profile went deeper than in other portions, as if the operator lingered too long on one spot. Any irregularity like this will have the bevels suffering for it, one way or another.

Blades that've been maintained exclusively on rod-type sharpeners or round honing 'steels' are also known to develop a recurve over time, in previously straight-edged profiles. The recurve in the vintage knife's blade, in the 2nd pic, reminds me of that sort of wear.
 
Obsessed with Edges said:
Yes, check for a warped, bent or bowed blade. It's very rare when there isn't any warp, bow or bend at all, in supposed 'straight-edge' blades like sheepfoot or Wharncliffe profiles. Even a tiny bit of warp, bow or bend will induce uneven sharpening patterns along the bevels, if sharpened on a flat stone.

Might also see it in blades with a wavy grind or uneven thickness of the blade. I have one knife where it can be clearly seen in one portion, that the belt used to grind the blade's primary profile went deeper than in other portions, as if the operator lingered too long on one spot. Any irregularity like this will have the bevels suffering for it, one way or another.

Blades that've been maintained exclusively on rod-type sharpeners or round honing 'steels' are also known to develop a recurve over time, in previously straight-edged profiles. The recurve in the vintage knife's blade, in the 2nd pic, reminds me of that sort of wear.
Click to expand...

Thank you so much for your response, much appreciated :thumbsup:

I always enjoy reading your perspective about sharpening issues here on blade forums.
Your insights on sharpening have proved invaluable over the past few months :thumbsup: :)
 
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