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Taking me too long to find a burr

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  • #55011
    Mark
    Participant
    • Topics: 3
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    I am very new to this sharpening so I am sure I am making new guy mistakes, many of them. Trying to sharpen a Henckel knife. I found the angles to be different at  12.7/10. Using a WE130 with the low angle adapter. Angle is measured with angle cube on low angle adapter. I was grinding away with a 100 grit stone for a least twenty minutes without finding a burr. Widened the angle a couple of times before I was able to detect a burr, then walked the angle back to the original angle. This process took forever so I am guessing I am messing up somewhere. When I was finally done the knife was very sharp but I think I could have manufactured a new knife in the time this took. Any help would be most appreciated. I seem to have the most difficulty raising a bur at the tip and the spine. Perhaps my knife positioning is off. Thanks for listening.

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    #55013
    MarcH
    Moderator
    • Topics: 61
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    Mark, 12.7º, or 10º is a very acute bevel angle and very uncommon for any knife.   I’ve only heard of a bevel angle like that just once.  It was from a regular longtime forum member sharpening a very special Japanese kitchen knife.  I rarely have seen anything lower than a 14º bevel angle and that’s on the finest, hardest steel, high-end, Japanese Chef’s knives.

    When sharpening used and older knives that have been sharpened multiple times over the years I wouldn’t look to match the existing bevel angles.  There’s no telling what angles you’ll find, now.  Instead, I’d look to re-establish a proper efficient bevel by profiling it to a bevel angle appropriate for the knife, the steel hardness and durability,  and how the knife will be used.  From my experience through the years with Henckel knives, for those knives like your’s pictured, I would consider profiling it at 17º to 20º, per side.

    When sharpening a knife, if you find yourself needing to exercise more effort then you’d expect should be necessary, like you wrote above, I’d look at where my sharpening strokes are removing the knife steel from the blade.  Applying marker ink, like a permanent “Sharpie” or “Marks-A-Lot” to the bevel, will help disclose where your sharpening stones are contacting the knife steel, by where you see the marker ink is removed with visual inspection.  Knowing this will clue you in on where your removing steel relative to the knife’s apex and help you to steer your sharpening efforts to the proper place.  Many of us use lighted magnifying tools like a jeweler’s loupe or a USB microscope to make close visual inspection easier.

    If it seems to you to be taking too long to form the burr, always make sure your working only on the knife steel and your not hitting the vise, the jaws or the low angle adapter with your sharpening stones.

    Marc
    (MarcH's Rack-Its)

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    #55047
    tcmeyer
    Participant
    • Topics: 37
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    I’ll add to MarcH’s excellent comments that using very coarse stones at very low angles is asking for trouble and for a couple of reasons:

    Low included angles have rather fragile edges, which will tend to break away, just as you are approaching the establishment of a burr.

    The bevel widths are larger with low angles, requiring the removal of more steel with each step up in grit.  The result is much greater effort/time at each step.  Coarser grits leave deeper scratches which require even more effort to remove.

    A major mistake made in this case was to increase the angle when it seemed to take too long to establish a burr.  This compounded the problem by suddenly moving the apex well below the intersect point of the current bevel planes.  Now the amount of steel removal required to move the intersect point back to the actual apex became huge (relatively speaking).

    I will also agree with MarcH that the correct angle for a Henckel should probably be in the 16 – 20 dps region.

    Separate comments on my personal methods in reprofiling an edge:

    I never use grits below 400 except where I’m reprofiling and then only where I can see clearly (USB ‘scope) that I am not too near the apex.  I know that many users freely use their coarser grit (50 – 200) successfully, but that hasn’t been my experience.  Some blades don’t seem to like them and are likely to fracture right at the apex.  Recovering from that kind of damage seems to take forever, so unless the owner has specifically asked for the edge to be reprofiled to a significantly different angle, reprofiling is reserved for repairing some sort of damage at the edge.

    In such cases, I will file a flat on the edge – until all the damage is erased.  The apex will now need to be re-established at or below the flat surface.  Now I am creating new bevels and with each stroke, bringing them toward the center of the edge flat, where the new apex will appear.

    Starting with 100 grit, I count strokes on each side – doing maybe 30 on one side, then 30 on the other, then repeat, all the while watching the edge.  When the edge flat gets down to about 0.25 mm wide, I’ll switch to 200 grit.  When it reaches 0.1 mm wide, I switch to 400 grit and keep with that until the new apex is well established.

    If the blade is longer than 3 or 4 inches, I will watch for uniformity of the width of the edge flat as I work the coarser stones.  If necessary (it almost always is) I will work sections with wider flats using scrubbing strokes, trying always to create an edge flat that is uniformly wide throughout the length of the edge.

    There are a couple of benefits to the practice of filing the edge flat to erase damage, but the main one is the reduction of effort.  All the steel above the lowest point of damage needs to be removed and narrow bevels are worked more easily than wide bevels.  With just a few strokes of 800 or 1000 grit stones, you will remove steel that would take dozens or hundreds of strokes on wide bevels to simply get down to new, undamaged steel.

    The second benefit is that the flat produced at the edge is harder to damage than an apex.  Accidentally hitting what is to be the new apex with a coarse grit will not produce the break-outs you’d get at a fine apex.

     

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