Shapton Kubo for professionals – user instructions
The Shapton Kubo for professionals is a tool that allows you to achieve a perfectly flat and true edge.
A good cutting edge results from the straightest, cleanest intersection at an acute angle between the bevel and the flat back of a cutting tool. But when sharpening a plane blade, the process of removing steel for a new edge also deforms or dishes the surface of the stone. Subsequent sharpening sessions will therefore alter the straight and flat edges of the blades. Achieving a really sharp edge takes experience, time, and effort. It is important to keep the variables to a minimum and to keep both the edges of the blades and the surfaces of the sharpening stones as straight and flat as possible.
Note: While we speak here of plane blades, these instructions also apply to chisel blades and other straight-bladed cutting tools like spokeshaves. With knives, the flatness of the sharpening stone is not so important, though one should be careful not to allow the stone to become too dished. This article does not explicitly describe the flattening and polishing of a blade’s flat side, but it is a similar process and the instructions apply in much the same way.
- Plane blade: flat side (only straight and flat is good!)
- Plane blade: bevel straight (good!)
- Plane blade: bevel rounded (bad!)
- Plane blade with straight bevel on a flat sharpening stone (good!)
- Plane blade with rounded bevel on a dished sharpening stone (bad!)
A combination of Shapton ceramic stones and the Kubo flattening plate makes it possible to achieve absolutely flat and true edges on plane blades and to keep the sharpening stone flat and true as well. Experience a truly flat and straight edge, such as you have never known!
- Kubo in rubber box
- Rubber box top view
- Rubber box bottom view
- Flattening plate in cast bronze
- Surface A – electrolytically diamond-encrusted surface for sharpening stones
- Surface B – electrolytically diamond-encrusted surface for tool blades
Note: Take care not to drop the flattening plate on the floor or subject it to other shocks or stresses as the plate can be damaged and lose its flatness.
- Surface (A-side) for flattening sharpening stones
- Movement of stones over surface
- Flattening action for stones
- Surface (B-side) for flattening plane or chisel blades
- Movement of blades over surface
- Flattening action for blades
- The closed Kubo rubber box provides a stable base for sharpening stones
Flattening sharpening stones
Place the flattening plate on a stable base. The A-side for dressing stones should face up. Wet the surface of the flattening plate. Also soak the water stones that you want to flatten, as if you were going to use them to sharpen a blade.
- Once it has absorbed enough water, place the dished sharpening stone on the A-side of the flattening plate.
- Make several passes with the stone over the flattening plate, applying moderate pressure, then turn it 180° and repeat. Repeat the process evenly in the two directions until just enough material has been removed from the stone to leave it completely flat.
- Finally pass the stone over the flattening plate, applying very light pressure. This last step ensures that the now very sharp edges of the stone are very slightly broken (relieved).
If you have several stones of different grit grades to flatten, rinse the flattening plate well with clean water before changing to another grit grade. If you flatten stones with a very fine grit structure, work very carefully to keep the flattening plate clean and free from larger grits that can get embedded in very fine stones and spoil their polishing action. On stones with a very fine grit structure use as light a pressure as possible.
If you use coarse grit stones on the flattening plate, the diamond coating gets worn down quite quickly. If you want to flatten very coarse stones, we recommend that you either rub two coarse stones together or use a plate made of silicone carbide
. This applies to stones with a grit grade under 500.
Flattening plane and chisel blades
Place the flattening plate on a solid base. The B-side for flattening bladed tools should face up. Wet the flattening plate thoroughly. Make sure you apply only moderate pressure when pushing the blade over the diamond surface and move the blade slowly so that it does not deform. Whenever possible, use the entire surface of the stone, not just one area.
- The surface on the left, about 80%, is used for blades of normal size.
- The non-perforated area to the right, about 20%, is for small plane blades and blades that may be damaged if they catch an edge or corner in the perforations, or for blades with curved cutting edges.
- If you want to correct a blade that has a curved edge, or a rounded bevel, then you need to start by grinding out an oval in the middle of the bevel.
- Pass the blade at a constant angle over the diamond plate to gradually enlarge this oval.
- This diagram shows a completely flattened bevel (the oval has disappeared into the edges of the blade).
The B-side for blades is not designed to remove notches in the edge. For this job you start with a coarse grinding stone.
The diamond face for correcting the bevels on plane blades is designed to touch up surfaces that are already almost flat. If you use the diamond surface often for coarse grinding, the abrasive coating will be used up unnecessarily quickly. Use the B-side only for final finishing for flat blades and perfecting their edges.
Also be careful when using the blade flattening side (B-side) not to damage the surface with a corner of the plane blade. The diamond particles in the relatively soft (compared to tool steel) nickel coating can be lifted off. Take particular care with narrow blades, as found in plow planes and mortice chisels.
Conclusion: For coarse work to remove a lot of material, use a coarse stone!
The following drawings show how to cross-sharpen a plane blade. This technique is ideal for dressing the bevel of a plane blade. In Japan this sharpening method is called "yoko-togi", where "yoko" means cross and "togi" is the basic verb for sharpening. The plane blade is held perpendicular to the length of the block and the bevel is then moved along the axis of the block. This makes it is easier to move the blade evenly and steadily over the diamond surface. In the West, the common practice of moving the blade with its wide edge forward back and forth along the length of the stone promotes the formation of a rounded bevel in the first place, as it is very difficult to maintain a constant angle when holding the blade freehand.
- Basic position for holding the bevel of the blade against the stone along its axis, or lengthwise.
- Blade movement. This is how a Japanese blade is held and moved over the plate.
Sharpening – an example
The steps involved in sharpening a blade differ depending on the condition of the edge.
If the edge is just dull, start with step D.
If the bevel is rounded, start with step C.
If the edge is in very bad shape, very worn and/or with notches, start with step B.
- Flattening the sharpening stone: Use the A-side of the flattening plate
- Grind out notches and other flaws back to a clean bevel at the proper angle: use a coarse stone until all flaws have disappeared. Compared to a medium or fine stone, the coarse stone quickly wears to an uneven surface, and as such is not suitable for obtaining a final flat surface on the blade. Do not use the flattening block for this job!
- To obtain a flat surface on plane or chisel blade: use the B-side of the flattening plate.
- Sharpening: Use a sharpening stone of medium grit, eg. a 1000 grit stone, and be careful that the more or less flat surface you created in the first step does not become rounded or deformed as you use the finer stone to improve the surface. If a blade with a flat and true bevel is sharpened, it should be sharpened over the entire surface of the bevel, and this should not be overdone. If the blade spends too long on the stone, the stone will begin to wear (to become dished) which will in turn begin to deform the bevel of the blade (to round it). In order to prevent too much wear on one stone, Shapton recommends the use of at least two stones with different medium grit grades, eg. stones with 1000 and 2000 grit grades.
- First honing: Use a stone with a fine grit for honing, and be careful to maintain the flatness of the stone. Again, it is advisable to use two stones with different grit grades, say 3000 and 6000 grit. If the blade has been well honed to an even flat surface at this stage, it will tend to adhere to the stone, in a kind of water lock. Even if you take your hands off the blade, it will stay erect on the stone. Note: this is not only true for the very thick and short Japanese plane blades!
- Mirror finish: Take a stone from about 8000 grit. These stones tend to remain flat longer because only a small amount of abrasive material is worn away in honing.
Enlarged representation of the electrolytic diamond coating. After extended use, the diamond coating of the stone becomes worn (see sketch). If this happens, the old diamond/nickel coating can be removed and the electrolytic layer reapplied.
- Diamond grit or abrasive
- Nickel plating
- Cast bronze