I managed to borrow a pretty expensive Dino-Lite digital microscope recently and thought I'd see how it did with bevel and apex photography. The subject of this little photo shoot is a Yoshikane white 2 bunka, which was touched-up on a Naniwa Pro 3k stone at around 12 degrees per side and then subjected to a few higher angle passes at around 15 degrees per side.
I found the microscope to be extremely sensative to changes in the focal plane (it was difficult to focus well) and the orientation of the bevel to the light source. I hope I'll be able to get better images with a bit more practice and a few additions to help orient and stabilize the blade.
The images themselves leave a lot to be desired imo, but they still show interesting features, such as the scratch pattern and compound 12 and 15 degree bevels. Possibly the most useful feature of the microscope is the in-built measurement feature where you can measure the distance between two parallel lines, angles, arcs, etc. I only used the distance measurement feature and before starting, I calibrated the microscope using objects with known dimensions at different magnifications. I used 3mm and 5mm alignment pins for the calibration and the post-calibration measurements seem plausible and I'd go so far as to estimate that they were accurate to within 2% of the actual value.
The micrographs show that my bevel width was actually pretty consistent from the heel to the point at which the tip starts to have noticeable curvature, namely the heel measurement was within 4% of the mid-blade measurement, which is honestly less variation than I was expecting. The bevel got noticeably narrower towards the tip (27% narrower than at the heel), indicating that I need to compensate more for the blade curvature when sharpening the tip. The bevel thickness that I measured when photographing the apex also matches the theoretical bevel thickness that can be calculated with a bit of trig, given that the bevel width and sharpening angles are known, namely:
Thickness at the top of the bevel = 2 x bevel width x sin(sharpening angle) = 2 x 0.235 x sin(~12) = 0.098mm
This is within 5% of the measured value from the microscope and I think that 5% difference can easily be attributed to the fact that my bevel is comprised of a ~12 degree bevel and a ~15 degree bevel rather than a perfect 12 degree bevel.
One point of interest is that there is a lot of reflected light from the apex, so either I didn't remove all of the micro-chipping / edge deformation with my quick touch-up, or I have a residual micro-burr clinging on for dear life.
I wouldn't necessarily recommend buying a microscope for analysing your sharpening, but if you have one lying around, it can certainly show some interesting features and help to visualise what is actually happening on your bevel / apex.
I found the microscope to be extremely sensative to changes in the focal plane (it was difficult to focus well) and the orientation of the bevel to the light source. I hope I'll be able to get better images with a bit more practice and a few additions to help orient and stabilize the blade.
The images themselves leave a lot to be desired imo, but they still show interesting features, such as the scratch pattern and compound 12 and 15 degree bevels. Possibly the most useful feature of the microscope is the in-built measurement feature where you can measure the distance between two parallel lines, angles, arcs, etc. I only used the distance measurement feature and before starting, I calibrated the microscope using objects with known dimensions at different magnifications. I used 3mm and 5mm alignment pins for the calibration and the post-calibration measurements seem plausible and I'd go so far as to estimate that they were accurate to within 2% of the actual value.
The micrographs show that my bevel width was actually pretty consistent from the heel to the point at which the tip starts to have noticeable curvature, namely the heel measurement was within 4% of the mid-blade measurement, which is honestly less variation than I was expecting. The bevel got noticeably narrower towards the tip (27% narrower than at the heel), indicating that I need to compensate more for the blade curvature when sharpening the tip. The bevel thickness that I measured when photographing the apex also matches the theoretical bevel thickness that can be calculated with a bit of trig, given that the bevel width and sharpening angles are known, namely:
Thickness at the top of the bevel = 2 x bevel width x sin(sharpening angle) = 2 x 0.235 x sin(~12) = 0.098mm
This is within 5% of the measured value from the microscope and I think that 5% difference can easily be attributed to the fact that my bevel is comprised of a ~12 degree bevel and a ~15 degree bevel rather than a perfect 12 degree bevel.
One point of interest is that there is a lot of reflected light from the apex, so either I didn't remove all of the micro-chipping / edge deformation with my quick touch-up, or I have a residual micro-burr clinging on for dear life.
I wouldn't necessarily recommend buying a microscope for analysing your sharpening, but if you have one lying around, it can certainly show some interesting features and help to visualise what is actually happening on your bevel / apex.
. Thanks for that.
