Gary Runyon;
BS and MS in Geology, specializing in metallic mineral exploration; 5 years with Getty Mining, 3 years with NASA working on Lunar rocks Past 25 years working in refractory powder metals as a metallurgist, predominantly tungsten carbide graded powders Part time knifemaker, helped develop (with Steve Schwarzer) forge welded mosaic Damascus using powder metals for knife work Rated (at one time) as a “Master” blacksmith, Do a limited amount of woodworking and toolmaking. I manufacture a spinning wheel for my wife’s exotic fiber business along with several other items for spinning and weaving.
2/2/2009
Harrelson,
One of the Lie-Nielsen A2 blades, that you supplied, was cut into 4 small blades, ~ 7/8-1” wide. These blades were labeled as:
A-Std
A-SharpSkate
B-Std
B-SharpSkate
All of these blades had a new bevel formed using an 8” slow speed grinder with a white Al2O3 wheel and a Veritas Tool Rest, angle ~27°. The back of each blade was flattened/polished to 30,000G. All of the edges, bevel side, were photographed to show the starting edge. These were then sharpened by hand using the two different jigs and the following waterstones. All of the stones were flattened between each blade using the DGLP (Diamond Glassline Lapping Plate).
1000G King
1500G King
4000G Norton
6000G Shapton GlassStone
8000G Norton
16,000G Shapton GlassStone
30,000G Shapton GlassStone
The microscope is a Leica DMRXE reflecting light microscope with a Leica DFC490 digital camera, Xenon light source.
The only difference between the “A” set and the “B” set was the “B” set was jointed at 1000G, 1500G, 4000G, and 30,000G. Two sets of photographs were taken at each stage labeled as “A” and “A1”, etc. As you can see from the Matrix Sheet several of these images were lost in our system.
Comments: First, I’ll make no claims that I am the greatest sharpener. I did the best that I could to sharpen all blades equally. I have also never used a sharpening jig before this comparison. In the past, all of my sharpening has been done by hand. The standard jig consisted of a roller in back and two side handles with the blade to be sharpened being pushed forwards and back on the stone. I found this to be a cumbersome jig to use ergonomically. It was easy to cause the blade to dig into the stone and it was difficult to use the entire surface of the stone. It also did not lock the blade in very well. It would be difficult to hone a slight curvature into the edge with this jig. You would probably have to do this by hand with the blade removed from the jig. Personally, if this was the only jig I had, it would never get used!
The SharpSkate was much easier to use. The ergonomics were great and it allowed the use of the entire stone. Digging in by the blade was a non-issue. Also, the SharpSkate locks a blade in almost too well. It took some getting used to in setting the tension just right to be able to adjust the blade to the proper position before locking it down. Once it was locked, there was no movement whatsoever. It was also easy to use this jig to hone a slight curvature into the edge.
My general impression between the edge generated by movement perpendicular to the edge (Standard Jig) and a sideways movement (SharpSkate) is that the sideways motion produces a smoother, less jagged edge. The difference between the two decreases as you progress through the finer stones. There is a large difference between the blades that were jointed versus non-jointed. The jointing removes the ragged edge and the burr. Rehoning of the edge after jointing, basically produces an edge with a much smaller burr. One of the things I noticed throughout this test was that there was often a very small remnant burr still on portions of the edge, even after supposed removal by honing the back. These remnant burrs were so small that they were not discernable by feel. At the coarser stones (1000G), I think the predominant advantage of jointing is removal of the burr. Removing this large burr allows a faster progression through the finer stones. Since this was the initial sharpening after grinding, removing this large burr seemed to be the biggest benefit. If the blade was being rehoned this would not be as big a factor.
At the end of the day, the blades that were sharpened using a sideways motion had an edge that was slightly less jagged. In all cases, the jointed edge was smoother compared to one that wasn’t. However, all of the blades that were sharpened to 30,000G showed extreme sharpness. They all showed some level of microdefects when examined at 500X. Jointing the edge appeared to help in two ways. First it produces an edge that is very flat with no protrusions or valleys. Secondly, it requires the blade to be resharpened on the same stone to remove the slight flat on the edge. This resharpening provides a slightly better prepared surface for the next stone (I think). The A Std blade that was honed on a piece of maple with 0.0-0.25um diamond paste showed a significant improvement of the surface polish. This polishing was comparable to a metallurgical polish that is used for evaluating the microstructure of metals. After the diamond polishing, actual carbide grains were discernable in the microstructure without etching. The implication of this is that the surface left by the 30,000G stone consists of very minute scratches that were easily polished out. My impression is that this polishing did not greatly reduce the number of defects on the edge.
I wasn’t able to compare the performance of these blades in use, but I suspect that the side sharpened blades that were jointed would provide the best edge retention. Ergonomically, there is no contest. The SharpSkate was much easier to use and, at least on these four blades, seemed to produce a better edge. I did see one instance (B-ShrpSkt 500X) of microfracturing on the edge, Possible this was caused by work hardening of the edge. I, inadvertently, hit the edge of one of these blades against the side of the microscope lens while photographing these. It is possible that this damage could be the remnant of this. Since I didn’t take note of which blade this happened to, I cannot tell if this is the cause.
Best regards,
Gary Runyon
2//3/2009
In regards, to your jointing process in sharpening, I believe that it produces a superior edge compared to standard sharpening techniques. In the process of evaluating the edge produced using a standard sharpening jig versus your SharpSkate, I noticed that burr removal was a very important component in obtaining a “sharp” edge. Examination of these blades showed remnant burrs that were not removed by a honing stroke on the back of the blade. Furthermore, it appears that the removal of the burr causes some metal on the edge to be pulled off with the burr. The result is small microdefects on the cutting edge. In my opinion, the predominant improvement of a jointing step is removing these defects and providing a planar surface to resharpen. The burr formed in the resharpening is smaller and therefore removal of this burr produces an edge with fewer microdefects. In every case, the jointed blades showed significantly fewer defects.
10/30/2009
I just wanted to give you some feedback on the last few months using the SharpSkate. I still use it for any major sharpening. If I only need to touch up an edge at 30,000X I’ll do that by hand. However, if an edge needs to be sharpened using a coarser stone, I grab the SharpSkate every time. I still feel that it is more ergonomic to use compared to a “normal” jig. I also still feel that the edge produced by side sharpening is better than the typical forward/back sharpening motion. I sharpened a very narrow Japanese chisel (~2mm) using the SharpSkate with very good results. I always have problems trying to sharpen this one, as it is so difficult to keep the bevel from rocking. The SharpSkate produced a much better edge than I could by hand. I just finished up a very small, 3” long curly maple handplane with an O-1 iron hardened to ~60HRC. The SharpSkate produced a very good edge on this blade and the plane works really well.
Anyway, take care. I hope you can use this feedback!
Best regards,
Gary