This 9×11″ aluminum plate allows you to shape whetstones as arc-chords, so that you can put a concave (hollow ground) bevel upon a razor, knife, or other tool.
The concave profile can either be partially applied (= concave toward ‘rear’ of bevel, flat or convex at apex) or fully applied (= concaved through to apex, two curved arcs intersecting rather than two lines intersecting).
While this plate’s marketed towards straight razor users, it is nonetheless a revolutionary item useful in many fields of sharpening; any serious chef that only uses their own knives, for example, should own this device or something like it. No matter how good incumbent efforts, they know not what they’re missing, but as I always say, “comparison is the robber of joy”. Buy a spacing guide and put some concavity in to your fine chef knives and you’ll be shocked!
Learn all about stone-shaping here, from a gent who has forgotten more of abrasives and geology than I shall ever know!
You don’t need to create a concave bevel form for the entire bevel span, as it is still a huge benefit to merely thin the ‘rear’ 80% of the bevel’s width and finish on a flat/hard/fine finishing stone or a pasted strop (it is perpetually challenging to finish entirely on a length-convex whetstone, though my very best shaving results occur when using that lofty goal).
In the razor realm, the historical preference for honing upon a fine foot powered natural stone wheel (‘turn’ to ‘page’ 33) was that by thinning a razor bevel directly at the factory [or at a local sharpening expert bestowed with a Pike Arkansas wheel], you would:
- increase the sum area of steel thinner than human hair (= the portion that ENTERS hair, thicker metal just “squeegees”/cleaves it away)
- increase the flexibility of the apex (so it penetrates hair more easily when presented at ideal angle, and conversely makes it *harder* to penetrate when presented at poor angle, the same reason why thicker-ground razors are typically easier than thinner-ground razors for novices to use)
- ease the home user’s re-sharpening with flat hone(s) or pasted strop by ensuring their efforts *must* affect directly upon the apex (for there could not be metal present just behind which could obstruct a flat stone, while if a bevel is ‘flat’, or more likely slightly convex, that obstruction is a perpetual problem).
It is important to understand that as a pair of fixed-shape tools which this plate (and sandpaper) produce from within a rectangular whetstone, they are not as advanced as an old (and long unobtanium) Pike Hard Arkansas wheel. For any given razor size, there will be a perfect diameter wheel which, if held upon the razor with spine and edge flush, will first touch the razor toward the rear of its bevel, away from its apex but also away from its hollow grind zone. Too short a diameter = sharpening scores the hollow grind zone. Too long a diameter = little benefit from the created hollow grind in bevel, as it will only deflect the apex and first 0.1mm worth of steel thickness, and then only slightly.
Ideally for straight razors, you would want to thin the bevel’s “shoulder” by ten microns or more, and finish with an abrasive field that initiates interaction jusssst behind the apex, but not far enough behind to leave >0.1mm of steel “above” it.
When you shape your whetstones so that their length faces the 9″ axis of this shaping tool, you’ll end up with a ~6.5’Ø (~2mØ) form. While in theory each razor size should not care if the bevel angle remained consistent between them, in practice you will find that smaller width razors have slightly larger inclusive cutting angles and larger width razors have slightly smaller inclusive cutting angles. On most 4/8″ razors, the 6.5’Ø minimum shape provided by this tool is still a little longer than ideal, and thus your honing will still hit forward of your bevel’s “shoulder” in the first step, limiting the ability for it to thin the razor bevel at the shoulder. You would need a smaller wheel to perfect such razors, and this tool cannot provide you that. Wheels (and wheel shapes) fine enough for this sort of work are scarce!
On a 7/8″ razor, on the other hand, the 6.5’Ø shape is not so short that it comes to initial contact within the razor’s hollow grind, but close enough to that that sharpening slurry will affect the appearance of the hollow grind (which is always a ‘risk’/tradeoff, and more prevalent the larger the razor width becomes, or the lower its cutting angle becomes).
The absolute ideal goal in honing on a wheel should be to thin the bevel and then finish with a stone which will touch jusssst behind the apex.
Shaping the stone so that its length faces the 11″ plate axis results in a ~25’Ø x ‘6.5Ø elliptical form. This shape will do a good job of gently flexing the razor’s apex as it sharpens on *any* razor. But the same cannot be universally said that shaping for a ~6.5’Ø x ~25’Ø stone will do a good job of gently thinning the razor’s bevel for all razor widths/cutting angles. It is much better than nothing, to be sure, but the old days had a twelve inch diameter, foot-powered stone of superior fineness, something so small it would cut in to the hollow grind of even the smallest width razor were it held flush at spine and edge. And so, via tremendous acquired skill, back then they on-the-fly created thinness to the bevel by varying the spine’s position above the small wheel as well as varying how much of the tiny bevel interacted with the wheel, all by free hand! This plate’s shorter-diameter-shape is terrific for thinning the bevel of 6/8″ and 5/8″ razors, less effective at bevel-thinning for 4/8″ and smaller razors, and is best served by incorporating a thin layer of tape on 7/8″ and larger razors. Whatever the razor size, using a hone created by this shaping aid does not require “tremendous” skill, only modest skill.
Current plate stock is 100% made in the USA, with carbon-neutral production!
If you’ve read this far, below are videos worthy your time