Hewn & Hone knife jig--report

[GKC]

I bought, and have now tried, the new knife jig for Tormek (or similar machines) made by "Hewn & Hone, a sharpening supply outfit founded by UK blacksmith Nic Westermann.  There are instructional videos on the Hewn & Hone website. Some of my pictures and a sketch are attached below.
 
Apologies for this book-length post, it is half the length of my original ramblings and still seems to go on.  Conclusion: The jig is quite specialized but excellent at what it was designed to do.

The jig is optimized for grinding scandi bevels on "sloyd" blades (relatively small wood carving knives).   It sells for £84, or about US$105.

Westermann is an advocate of the traditional approach of starting with a hollow grind for the shaping of the scandi (wide) bevels on sloyd blades.  The Tormek and similar machines can be perfect for this as long as the grind is repeatable.  Otherwise, too much time and steel are wasted reshaping the wide bevels on each trip to the wheel.  The objective of the jig is to put (as close as possible to) exactly the same bevels on a blade each time it goes on the wheel.

Once the bevels are hollow ground, a narrow apex bevel is sharpened on a flat surface (stone, diamond plate, abrasive film, etc.).  The flat surface contacts only the outside edges of the hollow grind, so the same angle of the scandi grind is maintained at the apex bevel.  You can sharpen the narrow apex bevel in this quick manner multiple times before having to go back to the wheel to redo the whole scandi grind.  (There is a discussion of this by me and a sketch by CB in a thread on scandi grinds: https://forum.tormek.com/index.php?topic=3680.msg25257#msg25257)

Interestingly, Westermann recommends using a dry CBN wheel on the Tormek (or similar machine) with this jig.  CBN because it is fast and the wheel stays a constant diameter between grinds; dry because scandi carving blades are often (by preference) in wooden handles that are vulnerable to the water involved in wet grinding.   I used the SG-250 wet and kept my handle dry with tape, but I can see the place for a dry CBN wheel on the Tormek in this application, especially because its constant diameter enhances the repeatability that the jig is aiming for.

The jig:   The jig is very accurately machined, albeit in a starkly functional way with no attempt to be pretty.  The blade is clamped in the jig by tightening two countersunk machine screws with an Allen key.  Having two screws spreads out the stress on the jaws and allows for clamping a blade with tapered thickness.  More on this below.
 
The three main design differences that I see between this jig and the Tormek knife jigs (SVM-45 and SVM-140) are that:

(1) the Tormek jigs hold the blade by having a moveable jaw tighten against a fixed jaw, whereas the Hewn & Hone jig has two fixed but (slightly) flexible jaws that are pulled together to clamp the blade;

(2) the Hewn & Hone jig is optimized for scandi grinds, such that the thin jaws of the jig—much thinner than those of the Tormek jigs—can grasp the small blades very close to the grind and still clear the wheel; and

(3) the Hewn & Hone jig is optimized to hold a relatively small blade in a set position each time the blade is mounted in the jig, so that the grind is accurately repeatable in subsequent bevel shapings on the wheel.

1. Self-centering jaws:  The design of the jaws results in a "self-centering" grip of the blade, whereas the Tormek SVM-45 and 140 jigs do not.  For knives that are thicker or thinner than ~2mm thick where they are clamped, the Tormek knife jigs hold the blade at an offset from the centre line of the shaft of the jig.  If not somehow compensated for (by shimming or thinning the fixed jaw of the jig, as required) this results in the grinding of unequal bevel angles.

Now, one feature of the particular self-centering design of the Hewn & Hone jig—basically a pair of jaws machined into a solid block of steel—is that it has a much more limited range of opening and closing than the Tormek knife jigs.  To move the jaws, you have to flex two sections of solid steel, so the gap between the jaws can only be varied by a relatively small amount: the range is from a minimum of 2mm to a maximum of 3.3mm.  With the (recommended) use of a protective gasket (such as a piece of paper or cardboard) between the jig and the blade, I found that the effective range of blade spine thicknesses that I could fit securely in the jig was about 1.5mm-3mm.

2. Thin jaws:  I have found the SVM-45 and 140 Tormek jigs to be too bulky to do a scandi grind on a small blade without the jig hitting the wheel.  I don't consider this to be a fault in the Tormek jigs—they are just designed to accommodate wider (and a wider range of) blades than this specialized jig.   The Hewn & Hone jig has very finely machined, thin jaws (see pic).  They have been machined to a fine point so that the jig clears the wheel even when the bevel comes within a few millimetres of the point where the jig is holding the blade.  (Note that, even with this thin jig, you have to be alert to avoid grinding the jig itself.)  Because the jig is machined out of steel, the jaws are strong even though they are thin.

3. Fixed angle mounting: The third difference in the design of this jig is that it is optimized to hold a typical sloyd blade, which is somewhat triangular: wider at the handle and tapered to a point.  And unlike the Tormek jigs, this jig is machined with a groove that will hold the blade at the same fixed orientation to the wheel each time it is mounted in the jig (see attached sketch).  This fixed orientation will tend to be approximately perpendicular to the wheel, which is generally what you want, but the more important thing is that it will result in grinding the same bevel each time the blade is mounted in the jig.

This should make the grind closely repeatable for subsequent shapings of the same blade.  You can "override" this feature by not pushing the blade to the angled back of the mounting slot, but then you are on your own for repeatability.

Trial: Once I had fitted a few blades into the jig I found it quite intuitive. It required considerably more attention than I give to the Tormek knife jigs.  The two machine screws should be tightened, back and forth, a bit at a time, and the same in reverse to unmount the blade.  I found this to require some dexterity, but I got used to it, and it works.  Once a blade is in, it is in solidly.
 
So, on the one hand the task of mounting is somewhat more fiddley, but on the other hand the task of getting it mounted in the same place the next time is much easier.  The latter is more important to me, so I can live with former.

To try it out on my T8, I mounted a new Frost/Mora 106 (see pic—flat ground scandi sloyd) in the jig and ground it on the SG-250 coarse, horizontal position.  The bevels came out as close to equal as I could measure. 

Then I unmounted the blade, Sharpied both of the new bevels, remounted it in the jig and put it back on the wheel.  It was pretty darn close to hitting at the same place all along both bevels: the marker was gone in one pass on each side.  So, on this blade the repeatability of the grind seemed to be reliable.

I tried this jig out on one of my kitchen knives.  It worked, but I don't think that is what this jig was designed for, and I would recommend caution using it on knives with wide blades.  A self-centering jig doesn't produce even bevels unless the blade is mounted in line with the shaft, and the narrow bearing surface with which this jig grips the blade creates the potential for missing, or failing to keep, that inline clamping position on a wide kitchen blade.

I also tried this jig on a small non-scandi blade: a medium-sized pocket knife blade.  It felt secure and more easily aligned with the shaft than with the Tormek small knife jig (SVM-00). 

I tried it on a tiny pocket knife blade, but the blade was too small: the jig hit the wheel.  So, this jig does not replace the Tormek small knife jig.

Side note for pivoters: Westermann advocates lifting, not pivoting, to keep the angle consistent along the curved section of a blade.  The stop collar of the jig is wide, to keep the jig consistently perpendicular to the wheel.  I am experimenting with pivoting the Tormek knife jigs on the T8, and will make one of my triangular collars for the narrower shaft of this new jig just to try it, but I prefer the simplicity of only lifting, so this jig works for me as-is.

In summary, this is a rather specialized jig, but in my initial testing I found it excellent for the type of blade it was designed for.  I have found hand grinding scandi bevels on flat surfaces to be tedious and sometimes inexact, and my impression is that a lot of carvers feel the same way.  This jig opens up a whole new way—faster and more exact—of coming at that task.

Gord

[Ken S]

Gord,

Thank you for a thorough and informative topic. It deserves serious discussion. I will be away from my computer much of the weekend. I will respond when I can give the thought it deserves.

Ken

[cbwx34]

Good review.  Definitely looks like a specialized jig, and wow does it look thin (although I understand why... I'm not sure I'd experiment too much...).

...
Side note for pivoters: Westermann advocates lifting, not pivoting, to keep the angle consistent along the curved section of a blade.  The stop collar of the jig is wide, to keep the jig consistently perpendicular to the wheel.  I am experimenting with pivoting the Tormek knife jigs on the T8, and will make one of my triangular collars for the narrower shaft of this new jig just to try it, but I prefer the simplicity of only lifting, so this jig works for me as-is.
...

There seems to be a bit of confusion on this.  Knives that don't have a lot of curve in the belly/tip area (and/or don't change their position much relative to the stone), really don't 'benefit' (or should I say, won't see much difference), pivoting vs. following Westermann's recommendation.  Knives like you pictured, I would use the lift method also... (especially the way you have it set in the jig, and the overall design).

Informative review though... tells me a little too specialized for my needs... but for the purpose, looks well designed and made!

[Ken S]

Gord,

I had some quiet time to study your review. Well done and certainly not too long.

I think of the utility of Tormek's jigs as being like a parabola. Using knives as an example, the standard kitchen knives fall into the top (maximum utility) of the parabola with Tormek's knife jigs. The further we deviate from "standard", the dicier things get. We can extend the range with things like Tormek's small blade tool for small carving blades with substantial handles; Rick's pivot for curved blades; Herman's small platform for lots of things; specialty support bars from Robin Bailey and Tormek, etc.

The Hewn and Hand jig seems very well designed for the scandi grind sloyd knives. Anyone working with this style of knife should have one or at keast give it a serious field trial. I have long believed that the versatility of the Tormek extends far beyond the standard jigs and accessories. Building for a niche market, Nic Westermann would not have the constraint (as Tormek does) of having to design to handle a wide range of tools. He can rightly zero in on optimizing his jig for a very small subset of knives. For an organization like a school, with a large number of this small subset, this kind of a specialized jig would be ideal.

Gord, I admire your pioneering spirit. Sometimes we just need to buy or make something and put it in service. Succeed or fail, that is how we learn. I hope you will continue to post your experiences with this jig from time to time. I trust your experiences with it will continue to be positive.

Ken

[wanderingwhittler]

Gord,

Thanks for taking the time to share your thoughts and experiences through such a thorough report. I've received mine as well and was quite happy with how it worked on a Mora 106. I have another Mora 120 that I'll eventually use with it and look forward to comparing the results and experience with the Hewn & Hone jig to that of the SVM-45 + SVM-00 that I used for my first-to-regrind 120.

I also tried it to hold a hand forged puukko, but that did not work out. The blade's rhombic cross section was not a good match for the jaws. That's not a surprise though, and is not what the jig was designed for. I only mention it to point out that it's not a magic bullet for all scandi-ground knives.

I'm pleased you had success with it holding a medium-sized pocket knife blade. I have not yet tried that, but I'll keep it in mind as a possibility.

Greg