While on a long bus ride across coastal Uruguay, I got to thinking again about the problem of using my jig with water stones or oil stones. An earlier, very elaborate solution, did not work.

My jig must slide on a flat smooth surface in the plane of the surface of the stone. The problem is to produce this surface. The solution turned out to be quite simple: build a vise with one wide, smooth jaw. Put the stone in the vise, with the surface of the stone level with the wide, smooth jaw.

Well, I have made four versions of the vise now, slowly improving the design. This pages shows the jigs in the order they were built.

Version 1 -- wood. The prototype, made of Ash, had all the features, but got very dirty when used with water stones. Do people wear hazmat suits when using water stones?
Version 2 -- plexiglas. This gets me close to the Tom Swift class. Worked well, but it turns out wood does not slide that well on plexiglas. This is not a problem when doing a primary bevel, but when I wanted to use the slips for the microbevels, the jig kept slipping off the slips.
Version 3 -- wood. Maple this time, rather than Ash, aiming for the slipperiest surface possible. The wide face was finished with Tung Oil, then waxed.
Version 4 -- wood and glass. This version is much longer - long enough to allow me to use the full length of a 12" bench stone, with an appropriate jig. The appropriate jig is pictured.
Sketchup drawingsI have recently started using Google SketchUp to draw the various jigs I designed and built. The new Jig Geometry page includes sketchup models of a couple of tool holding jigs as well as models of a triple stone, glass surfaced stone vise.

Version 1

Top view of the stone vise holding a small hard Arkansas stone. You can tell from the length of the threaded rod that it will handle stones up to about 9" long. That is a Hock iron in one of my jigs resting on the wide side of the stone vise.
Side view. The vise is taller than it has to be. I have one very thick water stone, so I made the jig pretty tall. The plane iron jig could be taller, allowing you to make use of more of the wide vise face and thus more of the stone.
The end view, with detail of the sawn slots for the threaded rod. The washers beneath the nuts are inset a bit into the end of the vise, helping to keep the rods from moving up and down in the slots during tightening.

Using the Stone Vise

Check that the stone and wide face form a flat surface using a long straight edge. Assuming a 5" wide vise face and an 8" long stone, then an error of 1/32" (straight edge high or low) at the vise-stone junction corresponds to an error of .22 degrees, which is acceptable. Flat is best.

An error means that either the front support is not square to the top, or the stone ends are not square. The second problem is hard to correct with this design, but does not arise in the Version 3 design because the stones rest on wooden blocks.

The vise appears to be able to easily hold the stone well enough for sharpening with only finger tight pressure on the wing nuts.

With my particular hardware, turning the wing nuts turns the threaded rod inside the nuts on this end, but it still gets the job done. You might want to use wing nuts on both ends.

Experience

Version 2

The top view of the stone vise. The wide jaw is about 6" front to back, 8" across. The narrow jaw is 1" thick - laminated 4 1/8" thick pieces. This stone is less than 2" wide - unsuitable for plane irons in my opinion. A 3" wide stone is one the way (not here June 7, 2004).

This side view shows that the vertical pieces have only one section that actually touches the table top. The thickness is only necessary to prevent bending as you tighten the thumbscrews, not for support. With only one supporting piece it is much easier to joint to width. While you can plane Plexiglas, a 1" wide section is not that much fun. The plane iron is not at the correct extension for a primary bevel angle of 25 degrees. The jig is 2-1/2" tall under the blade, so the correct extension is just over 5-1/2". The plane iron edge is then over 6" from the bottom front of the jig, allowing use of a good part of the stone.

Version 3

First, the vise does not grip the stones, but pieces of wood just a bit longer than the stones, called stone supports here to distinguish them from the vertical parts of the vise, which are called simply supports. This removes any danger of breaking thin stones.

Second, because the vise grips the stone supports rather than the stones, it is no problem to hold several stones at the same time. This is a big advantage since there is no set up time between stones - all the oil stones are available all the time. In fact, you need only set up the version 3 stonevise once. When you are done, lift the stones off and put them away. Next time just put the stones back in the same place and you are ready to sharpen.

Side view. Notice the stone thickness - just 1/2". The wooden supports are just a bit longer than the longest stone. The threaded rod runs between the supports, at about half way vertically to balance the pressure. If you had stones of different thicknesses, you would vary the position of these rods. As before, set up is done with the stone vise up side down on a smooth surface. First place the stones between the rods, then the place the wooden stone supports on the stones, then tighten the screws. Since the stones are not held tightly by the stone vise, you have to be careful when you turn the stone vise over. In this version, the rods only go through the front of the wide jaw. This means not only shorter rods, but it also means that tightening the wing nuts does not put any tension on the wide face, and hence does not bend it.

Top View The top stone is a Norton medium India, the lower stone is a Norton translucent Arkansas. The third slot could be filled with another stone, or with a strop. You could strop with a smooth piece of wood - in my earlier stopping tests I used a piece of Maple. You could also glue a piece of leather to a piece of wood. In either case, since the surface of the strop is level with the surface of the wide vise face, you can strop using the stone vise, treating the strop as any other honing surface -- except you only pull the blade along a leather strop.

Setup

1. place the stonevise face down on a flat surface,
2. put the stones between the rods,
3. put the stone supports on top of the stones,
4. tighten the wingnuts to bring equal tension on all of the stone supports,
5. lift the stonevise with captured stone supports off the stones and place it face up on a flat surface,
6. put the stones back onto their stone supports,
7. check the stones and wide vise jaw for flatness.

Version 4

The problem does not arise when using a wooden jig and wooden slips on glass. It happens, by chance rather than design, that there is less friction between wood and glass than between wood and wood. So the jig stayed on the slips when honing on glass and I did not notice the potential problem.

Although I use this stone vise mostly for grinding primary bevels (so don't often use slips on it), I still decided to glue on a glass surface. The reduction in sliding friction is worth the extra effort. I put glass on both faces - it seemed to be no harder than just putting it on the long face, and dimensioning the shorter face to match. I used 6mm glass. Thinner glass would probably work just as well.

Note It is a little hard to see in the picture, but the stone is not actually gripped by the vise. In fact, it is resting on a piece of wood (a support) that is gripped by the vise. The support is about 1/16" longer than the stone, so the stone can be lifted out and switched end-for-end, or flipped over. The tension rod placement, the support thickness, and the stone thickness must all be taken into account so the that support is between the tension rods (not above or below) in use.

This vise holds only 1 stone. I found that I was always using the 3 wide vise with a single stone, so made the new vise 1 wide.

I used Version 4 when doing the second round of bench stone tests and it worked really well.

Design Parameters

Error Analysis

If, for whatever reason, the stone surface is out of flat with the wide vise face, then honing will produce a rounded, rather than a flat, microbevel.

When the iron rests on the near end of the stone, there is a 1 degree error in the angle. When the iron rests on the far end of the stone, there is again a 1 degree error.

However, when the plane iron is half way between the two extreme positions the error is not 1 degree. It turns out that at the midpoint of the jig's travel, the angle at the edge is an extra 1/2 degrees (half of the amount of the error). So, over each jig motion the angle at the edge varies from 30 degrees, up to 30.5 degrees, and back to 30 degrees.

This means that only at the midpoint of the jig motion, when the angle at the edge is greatest, are you actually honing the edge. The rest of the time you are honing at a slightly lower angle, so you are honing a bit back from the edge.

The result is a rounded microbevel, not a flat microbevel. When you look at the iron to check for the presence and width of the microbevel, you do not see a single reflecting surface. Instead, since the microbevel is rounded, there is no angle at which it reflects the light particularly well. It looks like no microbevel is being formed.

I suspect that even the best hand honing produces this type of microbevel. Most people will vary the height of the back of the blade by more than 1 degree (which corresponds to lifting the back of a 7" long plane iron by about 1/8"). The result is a rounded microbevel.

Fortunately, if you build the stone vise so that all the legs are of equal height, the stone face will be flat with the vise face.

Navigation

Return to the Nitty-Gritty page.

Return to the Sharpening home page.