I’m wondering if it might be useful to have a separate thread on the HobbyGoni? I know it appears a couple of times under other topics, but suggest it might be useful enough to deserve a topic of its own? I’ve owned mine for a couple of months now and only lately discovered what a valuable asset it is. For those who are not familiar with this device, it is a laser product for determining the existing angles on a knife, available from England, running about $150 including all the taxes and shipping to this country.
While in theory it only reveals angles on each side of the blade to within 2 degrees, I find with mine I can easily determine the angle accurate to 1 degree. More important, it reveals the quality of the edge. If the edge is perfectly ground, perfectly flat, the angle shows as a very tiny circle on the scale. If there’s any kind of burr remaining, or secondary angle, or rounding of the edge, the point of light shows as more than one point, or as an elongated blur of light on the scale. Sometimes, I’ve had difficulty telling if there is still a slight burr by feel; the HobbyGoni clearly shows if there is a burr remaining.
While $150 is not a trivial expense, I’ve spent far more than this on various stones and strops which I haven’t gotten the full benefit from, as I have not been able to tell if my technique is good enough to get the edge I had hoped for. I’ve found that even under a microscope, I’ve been able to tell how polished my edge is, but not how precise in terms of coming to a point, creating a flat grind, eliminating burrs, or achieving the angle I desire. The HobbyGoni is better for these issues, and also more accurate than a marker, as well as much quicker, for determining angle. The problem with using a marker for determining angle is it involves destructive testing. The HobbyGoni gives an answer much quicker and without altering the edge.
The other aspect of this instrument that is important to note, is that on first use, with new knives direct from the manufacturer, the Hobbigoni appears to give very crude, not useful measurements. This turns out to be the fault of initial grind, not the Hobbigoni. The Hobbigoni is simply revealing what is there. If the initial grind is crude, the pattern shown by the instrument looks crude as well.
So much for my rant as a new convert. I thought might be useful for others.
. Also convex edges sometimes provide an interpretation challenge.