40X Magnification

[Herman Trivilino]

Dissecting microscopes have a magnification that typically varies from 10X to 40X.  Recently I was examining some small pocket knife blades that I had sharpened at 40X magnification.

What an eye opener!

This is going to have an affect on my sharpening skills, I just know it, because I'm seeing mistakes that I thought I wasn't making.  I thought that I was maintaining the same bevel angle all the way to the tip.  I thought I was grinding the bevel all the way to the edge.  Not in all cases.  And tiny nicks in the edge that I was missing with a magnifying glass are easy to find.  Once I locate them and know where they are, I can then find them with the magnifying glass and can feel them as I slide the end of my thumbnail along the knife edge.

It's been discussed here that with certain steels it's hard, or maybe impossible, to see or feel the burr develop.  If I can't do that I don't know if I've ground the bevel all the way to the edge.  I'm going to see if I can train myself to see or feel the absence of burrs by verifying with the scope that they aren't there.

Supposedly with good light, shining down from above and behind, the burr is visible to the naked eye if the blade is held at the right angle.  I'll see if I can teach myself to find it.

And by the way, even when I do get the bevel right, I still see parallel scratches presumably left behind by the 1000 grit wheel, but not removed by the honing wheel.  I'll have to see if I can work on that, too.

It'll be interesting to look through this scope at some new knives and some new razor blades.  I don't have either available right now, but I will look at some new utility knife blades, they should be the same as the old single edge razor blades like the type you might put in a scraper.

[Elden]

Very interesting Herman. I imagine the utility blades will show a fair burr.

I thought that I was maintaining the same bevel angle all the way to the tip.

I am curious about this statement. Is this on blades sharpened using the the SVM-45 or the Ionut-Herman jig? Possibly both? If so, which one is varying the most?

[Elden]

Herman, I am also curious about your microscope. How high of a quality of one is necessary to function well? I see there is a wide range in prices.

[Herman Trivilino]

I don't think it's the jig, Elden, it's the operator. 

Last night I took that Buck 055 pocket knife and used the HK-50 to put a uniform bevel on both sides from tip to bolster.  I had to prepare the grindstone rough and keep checking with the scope.  When I finally got there I could see the finest of burrs but only with the scope.  It wasn't bright and shiny, but was dark and dirty looking.  I couldn't see it with the naked eye or with a magnifying glass under good light.  And I couldn't feel it.

I then prepared the grindstone fine and could see with the scope that the scratches were smaller and closer together.  The burr was still there and would switch sides as I ground opposite sides, as expected.  The honing wheel made the scratches smaller, polished the smooth spots between the scratches, and removed the burr. 

I would guess that the SJ grindstone would further refine the scratch pattern.

According to Ron Hock it comes down to a balance between these three properties of steel: corrosion resistance, sharpenability, and edge holding.  You can have any two of these properties, but not all three.  This knife is definitely corrosion resistant as I've had it for several years and there's no sign of corrosion or staining.  It seems to be very hard to sharpen (both in terms of getting it sharp and how sharp I can get it).  Therefore it may be that it'll be very good at holding this edge.  This is the first time it's needed sharpening.

[Herman Trivilino]

Herman, I am also curious about your microscope. How high of a quality of one is necessary to function well? I see there is a wide range in prices.

I don't know, Elden.  The one I have is an old one that was discarded because one of the oculars wasn't working, and since it doesn't have a built in light they figured it wasn't worth fixing.  I repaired the damage (an internal part had to be glued back in place) and use an old desk lamp for illumination.  The optics in this old scope are very nice.

If you pay too little you may end up with one with inferior optics.  When that happens you get blurring and discoloring around the edges of the images.  You don't want a regular microscope as those have too high of a magnification.  You want a dissecting microscope.  Mine has a series of mirrors so that the image is neither inverted nor reversed.