Best microbevel angle
Test procedure we used was to set a secondary bevel using a Japanese grit JIS #800 wheel (grain size ~ 15 microns), edge-leading;
then set a microbevel at a larger angle with an SJ Japanese grit JIS #4000 wheel (grain size ~ 3 microns), edge-trailing;
the edge was then deburred*, and sharpness tested with a BESS edge sharpness tester.
We tested microbevels at 0.2 degree interval from +0.2 degree to +1 degree (per side).
In other words, tested edge sharpness where the grit #4000 grinding angle was 0.2, 0.4, 0.6, 0.8 and 1 degree larger than the angle at which the grit #800 bevel was set.
We then repeated the test for the best scoring microbevel to rule out random factors, and tested that range at 0.1 degree interval.
The best edge sharpness gave microbevel of 0.5 degree larger, i.e. 1 degree inclusive.
It scored 50 BESS, which approximates to 0.5 micron edge apex width.
We needed these data ourselves for one of our sharpening methods, but given their practical importance, share here with the knife community.
Full test results follow.
Grit #800 set bevel was 15 degrees per side, i.e. 30 degrees inclusive.
Grit #4000 microbevel angle per side - BESS score on PT50B edge sharpness tester
15.2 - 200 BESS
15.4 - 70 BESS
15.5 - 50 BESS
15.6 - 65 BESS
15.7 - 90 BESS
15.8 - 100 BESS
16 - 105 BESS
-------------------------
Grinder - Tormek T8 (#800), and T7 (#4000).
Knife - SWIBO at 58 HRC from our rental pool.
Edge sharpness tester - PT50B Professional.
*Deburring was done by a single pass each side on a paperwheel with 0.25 micron diamond paste, set at the angle of the microbevel.
Test procedure we used was to set a secondary bevel using a Japanese grit JIS #800 wheel (grain size ~ 15 microns), edge-leading;
then set a microbevel at a larger angle with an SJ Japanese grit JIS #4000 wheel (grain size ~ 3 microns), edge-trailing;
the edge was then deburred*, and sharpness tested with a BESS edge sharpness tester.
We tested microbevels at 0.2 degree interval from +0.2 degree to +1 degree (per side).
In other words, tested edge sharpness where the grit #4000 grinding angle was 0.2, 0.4, 0.6, 0.8 and 1 degree larger than the angle at which the grit #800 bevel was set.
We then repeated the test for the best scoring microbevel to rule out random factors, and tested that range at 0.1 degree interval.
The best edge sharpness gave microbevel of 0.5 degree larger, i.e. 1 degree inclusive.
It scored 50 BESS, which approximates to 0.5 micron edge apex width.
We needed these data ourselves for one of our sharpening methods, but given their practical importance, share here with the knife community.
Full test results follow.
Grit #800 set bevel was 15 degrees per side, i.e. 30 degrees inclusive.
Grit #4000 microbevel angle per side - BESS score on PT50B edge sharpness tester
15.2 - 200 BESS
15.4 - 70 BESS
15.5 - 50 BESS
15.6 - 65 BESS
15.7 - 90 BESS
15.8 - 100 BESS
16 - 105 BESS
-------------------------
Grinder - Tormek T8 (#800), and T7 (#4000).
Knife - SWIBO at 58 HRC from our rental pool.
Edge sharpness tester - PT50B Professional.
*Deburring was done by a single pass each side on a paperwheel with 0.25 micron diamond paste, set at the angle of the microbevel.