First page of the Norton archive.

Japanese Skiving Knife Repair

Posted by is9582 on January 11, 2018 with No Commentsas , , , , , , , , , , ,

I have a really beautiful Japanese skiving knife that my daughter and son-in-law bought for me, while in Japan a couple of years ago.

 

The bevel side of the blade on the Japanese skiving knife.

The bevel side of the blade (already sharpened) on the Japanese skiving knife.

 

The back side of the blade on the Japanese skiving knife.

The back side of the blade (already sharpened) on the Japanese skiving knife. Wooden stop at left (next to the corner of the blade) is used to set blade projection for this tool, when in the Kell honing guide.

 

I was using it to thin some leather from a piece where it would blend with a joint, and I noticed it wasn’t sliding through the leather like it had when I got it. My eyes aren’t what they once were, so I looked at the knife’s cutting edge under some magnification, and what I saw just blew me away! The edge was chipped something terribly!

 

This is the cutting edge of my skiving knife, before repairing the chipping.

This is the cutting edge of my skiving knife, before repairing the chipping.

 

I’m the only one who has ever used this skiving knife and I always handle my tools very carefully, and it has never fallen from the workbench or come in contact with anything other than leather. I even made a leather sheath for this knife when I received it, so it would be protected.

 

The Japanese skiving knife in it's leather sheath I made especially for it.

The Japanese skiving knife in it’s leather sheath I made especially for it.

 

It is possible that the steel used in this skiving knife is not flawed at all, even though it would seem at first glance that the heat treatment possibly left the blade too brittle. This isn’t uncommon in the blade making world, as the outside (what I might call a skin, for lack of better terms) can be a bit too far towards the brittle side, but once this skin is removed, the remaining body of the blade is both hard and resilient.

 

Ok, so how the heck can I fix this, without spending hours at the water stones, and without using up half a stone? Now this is going to sound crazy to some, but you hold the cutting edge perpendicular to the 1000-grit water stone, and move the blade down the stone. I know someone is cringing just thinking about doing this to a blade, much less with the damage it will do to some water stones, but stay with me here. This is one of the places that the Shapton Glass Stone series of stones really rock (not that they don’t rock all the time), when you have a narrow tool (something like a 1/16″ chisel or the working the edge of a card scraper), that can plow furrows into your water stone(s). The Glass Stones have a much harder matrix that most water stones I’ve used, and I find they do a better job of withstanding these focused pressure situations, without leaving deep depressions in the stones. Ok, back to the skiving knife… I visually check the knife’s cutting edge after each pass on the water stone, so I don’t waste my time, the water stone or the knife’s steel, and continue until there are no remaining chips on the blade’s edge (not a cutting edge at this point, as this process creates a flat at the edge) of the skiving knife. You may be wondering why I would use this technique, rather than working the bevel as you normally do when sharpening. I find this technique to be much faster and very reliable.

 

The chipping is all removed, and you can also see some of the paths this took on the Shapton Glass Stone in the background.

The chipping is all removed, and you can also see some of the paths this took on the Shapton Glass Stone in the background.

 

Now that the chipping is removed, its time to work the bevel on the 1000-grit, until the created flat at the tip is gone. This will prepare it to be a very sharp blade! This skiving knife has an amazingly acute honing angle, and the handle can get in the way of some honing guides, when trying to work at this low an angle. I decided to use my Kell honing guide, as it could hold the blade for this type angle, even though I found it was just barely able to retain it. What I mean regarding retaining the blade, is the blade would try to pivot ever so slightly during use, even though I had applied recommended pressure with the Kell honing guide. It turns out the back section of the skiving blade has a little taper to it, rather than two parallel edges. I found I had to put strong finger pressure down onto the rear part of the blade, while I was moving the Kell guide and blade up and down the water stones, which kept the blade static. One way to determine if you have actually removed enough steel, so that the back and bevel meet in the perfect “zero radius”, is to hold the blade with the cutting tip facing up towards some lights. If you can see any reflected light from the tip (not the back or the bevel) then you still have a flat on the tip and should continue to remove steel from the bevel. When you reach the point where there is no longer any light reflected back from the cutting tip (and you can feel a small burr all along the edge, from the back of the blade), it is time to shift to your finishing water stone, which should be at least an 8000-grit or higher. I prefer to use my 1000-grit water stone to remove the burr from the back of the blade, as it only takes a couple of swipes, but it really depends on the situation. Now on to the finishing stone, for both the bevel side and then the back.

 

Here I've just finished sharpening the skiving knife on the Norton 8000-grit water stone, and the Kell honing guide is seen to the left of the stone.

Here I’ve just finished sharpening the skiving knife on the Norton 8000-grit water stone, and the Kell honing guide is seen to the left of the stone.

 

You should be left with an amazingly sharp tool! I tested my skiving knife on a piece of leather, and it cut through it like it was going through soft butter. This is a wonderful tool that is back in business!

 

Thank you for reading the article and please let me know if you have any questions or suggestions.

 

Lee Laird

LeeLairdWoodworking@gmail.com

@LeeLairdWoodworking – Instagram

Let’s Skate towards Sharpness

Posted by is9582 on February 7, 2012 with No Commentsas , , , , , , , , , , , , ,

I don’t know about everyone else, but even though I have a good sharpening routine, I’m always looking out on the horizon for something potentially better. I’ve either owned or used most of the current, and many of the older sharpening guides/tools, so I’m really looking forward to testing what ultimately is a new concept in sharpening.

One honing guide I’ve had on my radar for easily over a year, is the Sharp Skate. Actually, I recall seeing information on the Sharp Skate, before it had transitioned to v.2 and v.3, so it has been a fair amount of time. A friend of mine recently purchased v.3 and has been kind enough to let me test it out. With many tools/accessories, there can be a bit of a ramp up to get comfortable. This was exactly my experience with the Sharp Skate.

The Sharp Skate comes with a dock, which has grooves on both sides, that are each associated with a specific angle.

System components; dock front right.

I have to admit that when I saw this on the advertisements, I completely misunderstood how the dock worked. I initially thought the sharp edge of whatever tool you were sharpening, would fit into one of the grooves, registering the angle the same each and every time. Well, the last part was correct, but surprisingly, instead of the sharp edge, the bevel on the tool registers in the grooves. I was completely shocked. After trying the proscribed method and giving it the old college try, I’m not sure the dock is a fit for me. I’m sure many out there would disagree, and find the functionality of the dock wonderful, but I find it hard to tell in which groove I’ve landed.

Sharp Skate sitting in dock.

It turns out that my friend that loaned me the Sharp Skate, John Parkinson, had this same issue, especially when trying to work at a very high angle, like 45 degrees. This prompted him to make a projection angle guide, not too dissimilar to the one Deneb Puchalski at Lie-Nielsen Toolworks created. This guide makes setting the angles much easier than I experienced using the dock.

Projection angle guide for Sharp Skate (notice the shorter lengths for each angle).

I own a set of Shapton glass stones, which I keep stored away, that I reintroduced for the Sharp Skate test. I used the Shaptons, since they have a harder matrix, and will be less prone to grooving than my Norton waterstones. Sharpening a tool side to side, especially if working a micro bevel or small surface area, would seem to have a higher chance of creating grooves in a stone. Compare this action to a side clamping guide, where the bevel is 90 degrees to the direction of the sharpening, and it would seem all too obvious. Anyways, for this test, I thought I’d try the Sharp Skate on a chisel, an old block plane iron, and a skew block plane iron.

The chisel was fairly simple to set into the Sharp Skate’s alignment grooves, and using the projection guide, the proper angle was easily set. I did notice, while aligning the chisel, that a perceptible amount of side to side rotational movement existed until I completely tightened the main knob with my fingers. I checked the chisel, after a couple of strokes, and one corner was showing signs it was set heavier than the other. The slight bit of difference seems like it just might be from the “play” I described. As info, I verified the chisel was centered, both at the front and backside of the guide. Hmmm, interesting.  Ok, first attempt using this guide, so lets possibly chalk it up to user error. I went back at it, and using slightly different pressure, achieved a very sharp chisel with a more consistent bevel, in just a couple of minutes.

I refreshed the stones and jigged up the old block plane iron, again verifying it was centered, using the projection jig agin. This iron had an extremely small chip in the center portion of the iron, so I expected to spend some extra time on the 1000 stone. After a few strokes, I noticed heavier steel removal on one side of the iron again.  I again adjusted my hand pressure to change the results. On both original and modified techniques, I tried to use a non-arcing back and forth movement, so I was surprised how easily I could ultimately impart a small camber using only pressure. I like that flexibility, but also realize more focus is required, to make certain the iron’s shape is as desired. I sharpened all over the surface of the 1000 grit stone, which is actually one of the special things about this guide. The layout of the tool’s wheels allows it to sharpen tools up to the very edge/end of stones. Ultimately using the full surface, and if the user is paying attention, this can help prevent wearing a hollow in the stone. After finishing on the 1000 stone, I spent another minute on the finish stone, resulting in another very sharp edge.

Lastly, I wanted to jig up my iron from one of my 140 skew block planes. Since the iron is skewed by 18 degrees, and I didn’t see any reference to this angle on the Sharp Skate, I almost stopped (no pun intended) this part of the test. Luckily, I read the fine print in an included paper, that referenced one of the “hard” stops as 18 degrees.  (These “hard” stops are pre-drilled holes in the clamping plate, that line up with a hole just inside each end of the guide. There are hardened pins that fit down through both sets of holes, to hold alignment. When working with a square orientation tool, the pins are in similar holes, midway between the front and back edge of the plate.)

Hardened pins to the right, removed from the alignment holes in body and clamping plate.

 I breathed a slight sigh of relief and started to center up the iron. With the clamping plate set for a skew, one side sticks proud of the main Sharp Skate body. This somewhat gets in the way, when using the projection guide to set the angles, so I played around to find the correct angle, applying some Sharpie to the bevel, to provide feedback.

Bevel side of the blade showing the Sharpie applied.

  Initially, I had the iron set with a short projection, and it showed a potential problem that could occur.

The gold section in the upper right, with the three holes, is the thicker section that made contact with the stone.

Since the clamping plate (for lack of better terms) on the Sharp Skate, is thinner in the middle and gets thicker towards each edge, a short projection while skewed can bring a corner of the plate into play. Luckily, I was using light contact and paying close attention. As I set the wheels of the Sharp Skate onto the stone, and lightly engaged the bevel, I thought it looked like the plate might be touching on one side. I moved over to the edge of the stone, so I could slide onto the stone, from the side away from the projecting plate. As I moved slowly onto the stone, I saw the plate was acting as a stop, since it was out further than the iron, at the plate’s thickest point. As luck would have it, this setting was too steep of an angle. I adjusted the iron a couple of times, until I was satisfied with the angle, and this was out far enough that the plate no longer engaged the stone. I guess this is just something to keep in mind, if in fact you need a very steep bevel or micro bevel. With this final setting, I was able to rapidly, and accurately sharpen this somewhat difficult iron in just a matter of minutes. Very impressive.

Barely visible micro-bevel.

Overall I think the Sharp Skate version 3 is an awfully cool and functional honing guide. As I’d mentioned earlier, there is a small learning curve, and then it’s off to the races. I’ll probably continue to use some of my existing guides, but as this is so well made, there still may be a place in my sharpening stables for this tool.