Adventures in honing: freehand, laser-guided, and jig-guided

[Cyrano]

This experiment was intended to learn more about the three systems I have at hand for honing on the Tormek leather wheel:

(1) Freehand: This involves holding the blade to the wheel using only my senses to judge the angle. I adjust the angle so as to minimize vibration and sound, as happens when the edge face is making smooth contact with the surface of the honing wheel.

(2) Laser-guided: This is also freehand, but with the assistance of a visible laser guideline on the honing wheel.

(3) Jig-guided: This is using wootz' excellent Front Vertical Bracket (FVB) in combination with the SVM-45 jig and wootz' FVB applet.

I used three new samples of a cheap kitchen knife. The protocol to create a test edge on each knife was:

• Mount the blade in the SVM-45 knife sharpening jig.
• Mount the SG-250 standard wheel.
• Set the USB height using wootz' applet.
• Create an edge using the SG-250 standard wheel at 220 grit.
• Mount the DE-250 extra-fine diamond wheel.
• Set the USB height using wootz' applet.
• Refine the edge using the DE-250 extra-fine diamond wheel.

I chose to use the DE-250 to refine the edge, instead of using the SG-250 graded to 1000 grit, because I'm looking for ways to speed up my sharpening workflow. I find grading the stone takes considerably longer than switching to a new stone.

Results: None of the trials resulted in very good BESS values; microscopy shows why.

Honing freehand appears to have polished the entire edge face evenly, with some rounding at the shoulder and some rounding at the apex. Residual burr is visible:



Honing using a laser-projected guideline appears to have been done at too steep an angle. The shoulder appears untouched, the edge near the shoulder appears untouched, and there is significant rounding of the apex. The rounding of the apex creates a reflective surface whose glare obscures good visibility of the amount of residual burr:



Honing using the FVB appears to have polished the entire edge face evenly, with some rounding at the shoulder and just a bit of rounding at the apex. Residual burr is visible:



Discussion:

The presence of residual burr on the FVB sample is of most interest, as this technique is known to produce near-ideal results in combination with the SG-250. Procedural error is certainly possible, in the form of inexact measurements, inexact USB settings, sub-optimal manual control of the blade in contact with the wheel, etc.

Having taken care with the measurements and settings, and having enough experience with the SVM-45 jig to be reasonably confident in my manual technique, I am tempted to look for other possible reasons for the presence of residual burr after FVB honing. Possibilities which will be investigated with follow-up testing include:

(a) The steel used in the cheap knives is pathological, and forms burrs which defy normal de-burring technique.

(b) The burr formed by the DE-250 diamond wheel is intrinsically more difficult to remove than the burr formed by the SG-250 standard wheel at 1000 grit.

[Cyrano]

Additional experimentation suggests neither theory proposed above is correct.

(a) The steel used in the cheap knives is pathological, and forms burrs which defy normal de-burring technique.

I was able to remove the burr from the freehand sample by additional freehand honing:



The results from additional freehand honing were not completely uniform, as some regions of the edge had residual burr:



(b) The burr formed by the DE-250 diamond wheel is intrinsically more difficult to remove than the burr formed by the SG-250 standard wheel at 1000 grit.

Residual burr after honing with the FVB was seen on a sample whose last operation before honing was edge refinement on the SJ-250 waterstone:



Taken together, these two trials suggest a simple explanation for the presence of residual burr after FVB honing: imperfect setting of the honing angle is causing improper contact of the edge apex with the honing surface. This theory will be tested by sequential honing trials at increasingly steep angles.