The blade of a knife is sharpened to a thickness that allows for cutting. You would think that using a piece of steel that is 4 mm thick and has a sharp edge will be very effective. Instead of cutting through fibrous ingredients, you will have a wedge effect. For this reason, a knife requires grinding.
Grindlines form where a knife's edge meets the flat (the side of the knife). They can have lines that are smooth or sharp, and some of them are symmetrical while others are curved. It takes true artistry to grind nice bevels.
A blade's grind can have a variety of benefits and drawbacks. Some people try to strike a balance between both strength and agility. While every grind has its advantages, the thickness of the blade stock and the grind angle will have a more significant impact on the abilities of the edge than the grind itself.
You will obtain distinct variations based on the belt's grit, stiffness, amount of overhang from the platen, and knife angle. The only way to learn is to explore and decide which outcomes you like most.
For the fellow knife nerds, here is a video to explain grinders and platens for knife work.
Types of Grindlines
The Hollow Grind
Blade blanks are placed on a grinding wheel's surface or a belt circling a wheel to create a hollow grind, which hollows out the blade by creating a concave scoop. The diameter of the spindle will determine the hollow's depth. As a result, many hollow grinds will be pretty shallow, and it might be challenging for a beginner's eye to distinguish a hollow grind on many blades.
Observing how light reflects off a blade might help determine whether it is hollow ground. Does light bounce off the entire surface, or does it bend as you raise and lower the blade? A hollow grind results from the light reflection bending.
The hollow grind benefits from not substantially increasing the blade's thickness as other grinds do. This implies that the edge will remain almost as thin as when you originally received your knife, even after sharpening it—honing hollow grinds is often simpler than honing other grind types.
There is, of course, a drawback to the hollow grind. Hollow grinds are undesirable in big blades like machetes because less material holds the edge, which might break or rollover with heavy use.
The hollow grind will work splendidly if you require your knife to be a master slicer.
The Full Flat Grind
The full flat grind is exactly what it sounds like; the grind descends in a flat, straight line from the spine to the blade bevel. One of the most adaptable grinds is the flat grind. It might be super thin and sharp or thick and hefty. Or it might be a mix of the two. Depending on the shape, most flat grinds strike a fine balance.
The complete flat grind has a relatively narrow edge for excellent slicing and a thicker spine for robustness. The blade's sides have more steel removed, making it more straightforward to slice through materials and travel through them.
Full flat grinds often slice finer than saber grinds and are more robust than hollow grinds. Because of this, most kitchen knives have a flat surface that allows them to cut through food with no difficulty.
Practically the entire flat grind is one of the most common grinds since it is a fantastic all-rounder.
The Saber Grind
In a saber grind, the principal bevel does not entirely cover the blade's breadth; some is left unground. This can either be a flat or hollow grind. The term "saber hollow ground" indicates that the blade has a hollow grind that begins halfway down the knife. The Sabre Line is the boundary between the primary bevel and the unground section of the blade.
When artisans want to create a more robust blade, they use the saber grind. The stock is frequently kept a little heavier to fully utilize the stronger blade so that the cutting tool can withstand demanding use, like chopping.
The saber grind does not cut as well as other grinds with heavier stock. The saber grind is used in well-known military designs.
The Chisel Grind
There is no grinding on one side of the blade. It only has the major bevel on one side, and the other side appears entirely flat. A secondary edge bevel may or not be present in the chisel grind.
The chisel grind is simple to create because you only need to grind one side, and there is no requirement that the grind is symmetrical with the opposite side. Because there is just one face, the chisel grind is also simple to sharpen. A thin and sharp edge is created by sharpening the other side at a narrower inclination since one side is left unchanged.
Chisel grinds are typically uncommon and not used very frequently. Consider them a unique grind. A blade with a chisel grind tends to serve a specialised function, like that of Japanese single bevel Sashimi knives.
How to Produce Straight Grindlines?
- Determine the Point at Which the Grind Line Ends.
To begin, decide where the grindline should terminate. When you commence grinding, create it and stick with it. Professional knifemakers typically mark where their grindlines should end when grinding their bevels to align them with the tip of the belt.
It's wise to begin grinding below the grindline and move back towards the tip. It can be challenging to correct grindline faults early on; therefore, grind a reasonably shallow bevel, so you know your grind's precise location. Afterward, you can return to the angle and climb back up the knife.
- Maintain Symmetric Plunge Lines
From one end of the device to the other, grindlines ought to be symmetrical. As mentioned in the preceding tip, be aware of your desired bevel location. Place them exactly where you want them on each side and keep them there.
When flat grinding your knife, hang your belt over the platen's edge, which serves as a platform to support it. Keep grinding away after aligning the belt so that its edge and the platen's edge on both sides are about the same. By doing this, you will, under normal circumstances, obtain a straight and clean gridline.
- Adjust the Tracking
You may alter the curvature of the platen on your grinder by varying the tracking knob.
The grindline will soften up a little if the routing is adjusted, so the belt drops off the edge by roughly 1/8 of an inch, producing a seamless transition from the edge to the flat.
If you hang it off more (say, a quarter-inch), it will set everything off and modify the grindline at the top from a sharp corner to a curve.
- Use the Correct Belt for the Type of Grindline
With various belts, you can obtain varied plunge lines. Ceramic belts are often better at producing either extremely sharp edges or long, sweeping curves, but they're not so excellent at producing that in-between line where it hangs off by perhaps 1/8 of an inch. In that scenario, your standard aluminum oxide belt would be preferable for curves in between.
In terms of functionality, there is no distinction between soft and hard grindlines. The tougher ones are quicker and simpler to complete. This has particular benefits in production because you don't have to bother altering the tracker and can keep working. The soft ones require a little more finesse to complete properly, but it's easier if you do it by hand.
Do not rush the grinding process; instead, take your time as you pass the job back and forth across the belt grinder. A mistake here might have disastrous consequences. Wear latex gloves to prevent your hands from becoming wet when quenching the blade and make things safer.
It's time to complete the rest of your knife once you've got the blade ground.