We met up with our friend Greg the woodworker a couple months ago. He is actually very talented, and does a lot of testing and reviewing of new woodworking gadgets and tools for manufacturers. We got to talking about the sharpness and condition of his hand tools, and he took me up on an offer to sharpen up one of his chisels. Of course, I got a difficult one… Here’s the before and after pics.
With the success of my test by Greg, He promptly sent me a large pile of chisel and plane blades, some carbide tipped router bits, and a kitchen knife for good measure. The chisels and planes were easy enough, although they took some work. But the real challenge for me were the router bits. Carbide bits can only be sharpened with diamonds, and luckily I had some Jende Diamond Films on hand. It must be said that the Jende Diamond films are a general purpose film – and specifically in the case of these carbide bits, they are best suited for refreshing and conditioning the bits, and simply do not have the ability to remove or fix any chips. Most router bits cannot be repaired once chipped anyway due to the balance necessary for the bit to work and the usually tight overhang of the bit from its base. But what can be done is the refreshing of the “corner” that the bit needs. Below are microscope pictures of the router bit edges, taken with a Veho 400 microscope. The actual size of the pictures are 1 mm wide by 0.75 mm high.
Picture 1 shows a dovetail router bit edge as it was received from Greg. There is some roughness to the edge from use. The edge here is wavering. Since mechanized tools spin so quickly, ultimate refinement is not as important as creating a consistent shape of the edge as it impacts with the wood. Even though the Jende Diamond Films go as coarse as 80 micron (180 grit), I opted to begin with a 30 micron (500 grit) film and finish with a 15 micron (1,000 Grit) film. Because of the small size of the the bit, I used a 1/2″ wide piece of aluminum with some 6″ long PSA backed film that wrapped around the top of the aluminum to the other side, and basically made my own slip stone that would be easy to facilitate with the flatness of the dovetail bit as well as to manipulate around the curves of the cove bits. Here’s the picture of the slip stones after they crossed the finish line – 7 router bits later.
So by following the contours and angles of the bit, the 30 micron Jende diamond film packed an aggressive punch:
Not only are the scratches on the surface of the bit much finer, they are in the reverse direction. The edge of the edge is definitely much more “crisp” at this stage, with minimal chipping out at the edge as compared to picture 1. 30 micron is still pretty coarse in the grand scheme of things, and as mentioned before the shape is more important than the refinement. However, I usually take my mechanized edges up to 15 micron, or 1K. The 1K edge leaves a smoother finish, and the integrity of the edge stays intact better over time, IMO. Here’s the finished microscope shot:
The Jende Diamond Films can handle the carbide bits, and can give the edge another life or two.
Next up was a rather wide radius Cove bit. I did the same thing as the dovetail, only because of the rounded bit, I ran the slip stone along the curvature rather than running the bit across the surface of the film.
Notice the rounded edge of the edge. The Jende Diamond Films are perfect for taking the rounding out and refreshing the sharpness. Here’s the 30 micron results:
You can clearly see the original grinding lines that are perpendicular to the edge, and the 30 micron left to right scratches. Because of the rounded surface, it took a little longer to get the results I wished for. Also the carbide bits are slightly hollow ground from their original machining processes, and my relatively flat slip stone needed to work a little more to get a nice radius on the edge. Picture 5a shows the result of the 30 micron film after just a little longer:
The original machining mark is quite noticeable now against the 30 micron scratches. The edge of the edge is also straight now. I finished with the 15 micron (1,000 grit) diamond film, and the results are quite similar to the dovetail’s, if not a little better :)
In conclusion, the Jende Diamond Films can handle carbide bits, and a whole lot more! One of the best features about these films is that with the PSA backing they can be used effectively as slip stones in almost any situation. The wide range of grits also allows for consistency from 80 micron (180 grit) all the way up to 0.5 micron (30,000 grit).
Here’s the finished bit: