Wire Edge Prevention

[KnifeGrinders]

Real Life Check


I've sharpened a couple of boning knives (on the photo) using the deburring method detailed above, and have given them to a beef boning room. They have 7 bull "bodies" to bone and butcher on Monday, and tomorrow I will get the butchers' feedback - will then update here on how well the edge lasts.

Our production sharpening of boners is 4-step, 3 of which are deburring.
We aim at under 2 min per knife, and I have taken a few more photos to show how the all-controlled experimental setup translates into production sharpening.
For speeding up the process we do not clamp knives in a knife jig.

The edge is set on Tormek (90 RPM) on the side of a #400 CBN wheel, using our volume sharpening attachment.



Because the side of the wheel is flat, the edge geometry is pretty much the same as that off a benchstone. We set the edge at 12 dps, and this step is quite accurate - the CATRA laser protractor shows the edge angle of 12 dps.
Off the CBN #400, the edge has a burr that can be seen and felt by brushing your finger across it, and scores near 500 BESS.

Next step is deburring on a slotted rock-hard felt wheel with Autosol run on a half-speed grinder (~1400 RPM) - we do it at the edge angle, but because we use a horizontal platform to cotrol the angle, practically, of course, it is somewhere near. As we know, Autosol metal polish abrasive particles average 3-6 microns in size.
I had cut slots in the felt to cool the edge, and you can feel it actually blows air as a a fan.



At this step we thin away the burr and you cannot feel the burr anymore, and can hardly see some micro-fringe on the edge under certain light, but we know by microscopy that the edge does have a feather burr.
Interestingly, the BESS score is still near 500 BESS because of the feather burr mushrooming - looking just at the sharpness tester scores you'd say that we have done nothing to the edge.

Next step is removing the base burr using the method from the above experiments, on Tormek (90 RPM) on a rock-hard felt wheel with 1-micron diamonds at approximately 1 degree higher than the edge angle, i.e. in this case at approx. 13 dps.
Again, to avoid clamping the knife in the jig we use a horizontal platform to control the honing angle - and that's why I say "approximately".



The sharpness score is now 85-90 BESS, telling us we've removed the flimsy feather burr.

Final cleanup is done by 4-5 swipes on a hanging clean leather strop, alternaging sides - this improves sharpness score by about 15 BESS, and the final sharpness comes to 70 BESS.
Such a good score on mainstream s/s steel tells me that we've hopefully removed the base burr, but only a real cutting can tell if the wire edge is still there.
(Although the experimets have shown that a good final cleanup is achieved on a paper wheel with CHROMOX, the horizontal platform does not have the required accuracy of angle control, and we changed to the hanging leather strop.)

A short video on our volume sharpening: https://youtu.be/LP1_kjUC89U

In real volume sharpening we deburr on a single wheel with a 3-6 micron honing compound, by deburring at the edge angle and finishing at a higher angle by simply sinking the edge into the felt.
The above sequence of the 2 felt wheels was to "dissect" the process of deburring and better understand peculiarities of its different phases.

Residual stress check shows the BESS score worsening by 15-20 BESS in 17 hours, telling us of a low level of stress as compared to the typical 50 BESS we see after paper wheels.

We've agreed with the butchers that they will start the beef boning with our knives and continue with them as long as they last, steeling them the normal way they always steel.
The butcher I spoke to says he uses primarily the polished steel through the day, every 5-10 cuts, and the ratio of polished to fine-cut steel is between 10:1 and 20:1.
I will honestly update this post tomorrow night with what butchers say about our knives performance.