Thread: The Mysterious Missing Slivers of Edge

Originally Posted by Geezer

The above are all good possibilities!
Was the blade bread-knifed on a diamond plate to get it into condition? That can cause the effect, big time. I found out the hard way! It causes deep scratches along the bevel and they are often hidden by later honing.
~Richard

That is very true, Richard. I first saw evidence of this in an experiment by a promoter of shapton hones. He showed how some edges deteriorated and how the shaptons fixed the issue. What he did not disclose was that the edges (knife edges in this example, but the facts hold true for razors, too) were brought up to bevel-set by guys (at a knife makers get-together) using belt sanders with coarse-grit belts in the 220 - 440 grit range. When I queried how the experiment could possibly have any value, and after asking for pictures of the blades pre-shapton honing and post belt-sanding, it was obvious that the damage occurred in the deep gouge lines inflicted by the belt sander. It was amazing how some preliminary honing on higher grit shaptons masked the gouge lines, though I suspect that light and angle could have brought them out if necessary, although it would have blown the promoters point. In some case there were faint traces of the gouge line above the more refined bevels.

After this, I adopted quite a thorough stage of coarse grits, to be used if ever I had to resort to anything coarser than a 600 grit diamond plate. This involved, for arguments sake, 220 diamond, 400 diamond, 600 diamond, 1200 diamond then dropping back to 1000 grit chosera and finishing on these type of man-mades. I never go any micro-chipping after that, unless the steel alloy was too soft for the grit of the hone.

This was particularly easily observable on old Sheffields, who seem to resent high grit hones, Anything above 15k seems to be out of the question most of the time, which throws your shapton 16ks, SG20ks and shapton 30ks out of the window and opens the door to a good old hard coticule, or minimum laps on shapton pro 15k or an escher or some other form of natural. Hard coticule and soft Sheffield steel seem a natural pairing, though.

Some people scoff at the idea of old Sheffield steel being soft, and I agree in part - not all of it was, but it is demonstrable that some W&Bs are in the 58/9 rockwell hardness range (pretty soft - Solingen Standard minimum for razors), while others are much higher, getting into the 60, 61 rockwell hardness range, which is the sort of hardness you expect from decent Puma steel at one end and quite hard modern TIs at the other. Personally, I loathe anything over 60 - 61 rockwell!

Some other methods readily get rid of this fragile, 'false', 'burr' or 'wire' or 'fin' edge - call it what you will. The Tam O'Shanter is well known for use on steels apt to microchip, but as most Tams (other than the white variety) are fairly lowish in grit, then you still need higher grit finisher, so the micro-chipping may be induced again if you go this route. However for a decent grit Tam you can shave off its edge without a problem.

Some preliminary half laps or circles prior to the finishing hone often helps with steels with only a minimal propensity to exhibit this phenomenon.

Some stropping on a pasted paddle with chrome oxide before falling back onto the (lesser grit, chrome oxide = 0.5 micron approx. equal to a 30k hone) finishing hone often helps.


Regards,
Neil.