Thread: Headlamp for edge test

Dave, definitely need light. It doesn't need to be from directly above though. I personally prefer lighting from nearly perpendicular to the edge to get the best view of what is actually happening at the edge. For the bevel you want to be just a bit higher.

Here are a couple images taken with my scope. The first image is a setup of an edge I was doing some testing with. Two different stones tested side by side, honed with no tape first, then a layer of tape to get side by side scratch patterns. These images are both edges honed on coticule. The 2nd one is a HSS test edge with a slurry dilution. You can see the coticule wasn't able to get back to the edge after slurry honing.





Here is how I prefer to view the edge/apex:

How do you get the apex shot??
Vertical and turn down light source?
Is the edge supposed to look... sorry .... ragged or toothy?? No disrespect I haven't been able to get that view myself.

So this is what I use

There are a couple reasons the edge in that shot looks a little ragged. One is because it is a little ragged, lol. It's an edge that has been shaved with and also it's at about 250x (calibrated with an item of known size). If you don't have that level of magnification things always look pretty straight after a decent finisher. On top of that, it's a high speed steel razor - which doesn't cut cleanly with natural stones - diamond or CBN are needed to get a very clean edge. Here is a shot of the exact same razor finished on diamond:



I don't judge too much by edge appearance really, just checking that the apex is keen. That band of light in the apex shots is only a few microns wide. I can't tell you how many times I thought an edge looked awful at this magnification but shaved very well. A scope is a tool, not an arbiter of edge quality.

For lighting the apex I use a focused beam LED that basically collimates the light so it's all traveling the same direction in a straight line. I light up the edge from perpendicular to the apex with the light shining directly at the apex. The razor is positioned so that the bevel is parallel to the scope lens.

Originally Posted by eKretz

There are a couple reasons the edge in that shot looks a little ragged. One is because it is a little ragged, lol. It's an edge that has been shaved with and also it's at about 250x (calibrated with an item of known size). If you don't have that level of magnification things always look pretty straight after a decent finisher. On top of that, it's a high speed steel razor - which doesn't cut cleanly with natural stones - diamond or CBN are needed to get a very clean edge. Here is a shot of the exact same razor finished on diamond:



I don't judge too much by edge appearance really, just checking that the apex is keen. That band of light in the apex shots is only a few microns wide. I can't tell you how many times I thought an edge looked awful at this magnification but shaved very well. A scope is a tool, not an arbiter of edge quality.

For lighting the apex I use a focused beam LED that basically collimates the light so it's all traveling the same direction in a straight line. I light up the edge from perpendicular to the apex with the light shining directly at the apex. The razor is positioned so that the bevel is parallel to the scope lens.

You have just made my day. I now aspire to get images of apex like yours thanks for the tips. Beautiful apex picture in this post Sir.

First look at the edge straight down on the edge, if you see reflections, then look at it from the side with magnification.

For straight down view, low magnification 10-60x works best, same for USB scopes, but with good light you can see it with the naked eye.

Then higher magnification if you have it, for side view to determine the cause.

Here is a good video of how to view edge down by toxikwaste,

Straight Razor Sharp Test.