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A hollow edge on a knife is more often referred to as a hollow grind edge or a hollow ground edge, which means that the bevel is ground with a concave radius to it. This allows for a thinner, much sharper edge than many other types of bevel grinds. But what is the best way to take care of the edge on your hollow grind knife, and how do you sharpen it?
A hollow edge knife will hold the edge well, so a simple strop may be enough or sharpen the concave edge with these steps.
- Inspect the edge of the knife.
- Try stropping first.
- Choose your sharpening method, wheel, or stones.
- Sharpen the knife.
- Strop the knife.
You follow a few different paths to sharpen a hollow grind knife, but some will require specialized tools to maintain the concave curvature of the bevel to the sharp edge.
Because the edge on hollow ground knives is less robust, normally better steel is used to make these knives which improves the edge retention. This makes regular aggressive sharpening not necessary on these blades and simple maintenance a better option.
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How Are Hollow Grinds Produced?
Hollow grinds on a knife bevel are achieved by grinding the bevel on a wheel. The bevel will then take on the curvature of the wheel and result in a concave, r hollow ground bevel.
Hollow grinds have been around for a long time since man has been using a round grinding wheel for sharpening knives.
The radius of the grind can be varied by using grinding wheels of different diameters. A large diameter grinding wheel will produce a shallow hollow grind, whereas a small diameter grinding wheel will produce a deeper, more pronounced hollow grind to the bevel.
Why Are Hollow Grinds Used?
Hollow grinds are more often used on shorter knives or blades where sharpness and slicing ability is of more importance than edge durability for chopping actions.
For this reason, the hollow grind is generally put on shorter knives or blades that are going to be used for more delicate cutting tasks rather than rough work.
The nature of a hollow grind means that there is less steel mass behind the edge to support it. While this affects the strength of the edge, making it a little weaker than other grind types, it does offer some advantages.
The concave hollow grind allows the cutting edge of the knife to be thinner, which increases the sharpness level to which this type of grind can be sharpened.
Because the edge on these knives is considerably thinner than other grinds, manufacturers will generally use better steel that will hold this type of edge well.
This means that hollow grind knives often need less aggressive sharpening, and instead, the edge can be touched up and restored to sharpness by much simpler sharpening methods. It also means that the knife will need more regular maintenance with a strop.
Sometimes, however, the knife will require some more aggressive methods to restore the sharp edge of the blade. At this point, you will have some decisions to make as to how you want to tackle the sharpening.
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Step-by-Step: How To Fix A Broken Knife Blade In 5 Steps
How To Sharpen A Hollow Grind Knife
When you need to sharpen a knife that has a hollow grind, there are a few tasks you should perform first to see what level of sharpening the blade requires.
Most hollow grind knives will be made from good steel that will hold the edge well, which will also affect how frequently aggressive edge restoration is needed.
1. Inspect The Edge Of The Knife
The first task to undertake if your hollow grind knife has lost some of its sharpness is to inspect the sharp edge of the blade. In this inspection, you will want to establish if the edge has sustained damage or if it simply needs a touch-up.
If you cannot see any noticeable deformation of the edge in the way of dents, chips, nicks, or warps, then the edge is still in pretty good shape. A simple touch-up of the edge may be sufficient to restore the edge.
If, however, you do see damage to the edge, then a more aggressive sharpening session may be required to bring the blade back to its original condition.
2. Try A Stropping First
If you own a hollow grind knife, then you should also own a leather strop as well. A strop will be your best friend in maintaining the edge of your hollow grind blade.
The edge of a hollow grind is thin, and during the course of normal use, the edge can roll over, causing the blade to lose sharpness.
This does not indicate damage to the sharp edge, and it does not necessarily need to be sharpened; the thin edge simply needs to be re-aligned.
This is most effectively done by giving the blade a strop on a leather strop with some grinding compound on the leather.
You can strop a blade with different levels of aggression to fix different levels of dullness on the blade. Sometimes, a few strokes, 5 or 6 on each side of the blade, over the strop will be sufficient to re-align a slightly rolled-over edge.
If the edge is more severely rolled over, a more intense stropping session may be required where you add the additional grinding paste to the strop and spend more time stropping the blade.
This may involve several cycles of stropping on each side of the blade, using different grit grinding compounds on the strop.
Unless the sharp edge has sustained damage, a good stropping of the edge will, in most instances, be sufficient to restore the cutting edge to its original level of sharpness.
Whenever your hollow grind knife edge feels like it needs some attention, always try a stropping first to see if it sorts out the edge of the knife and restores the edge.
Stropping is also less aggressive and removes less steel from the blade than other sharpening methods do.
3. Choose Your Sharpening Method
If your inspection of the edge led you to the conclusion that your knife needs more attention than what a good stropping can sort out, then you have some decisions to make.
There are two main methods that we can recommend that you can use to repair the edge of the hollow grind knife and restore the cutting edge.
Sharpen the Knife On A Wheel
This first method is the ideal way to sharpen a hollow grind blade, but it requires specialist equipment. You will need a grinding wheel that has the correct radius for the hollow grind on your knife.
If you are a knifemaker and own a belt grinder, you can use a small wheel attachment on the grinder to fit different size wheels to the grinder.
This will allow you to select a wheel that has the right radius for the bevel, and you can re-establish the hollow grind and maintain the shape of the bevel.
Some bench grinders can also have different-sized wheels fitted to them, which will allow you to fit and use a wheel that has the appropriate curvature for the hollow grind on the knife.
As you can see, this method requires specialized equipment to sharpen the hollow grinds, and the average knife owner will not have access to these kinds of tools and equipment.
Many owners of blades with hollow grinds, such as straight razors, will often send these blades to professionals that have the right equipment to get them re-sharpened.
This makes sure that the curvature of the bevel is maintained, and there is no secondary bevel or micro bevel on the edge of the knife.
TIP: Even if you sharpen your knife correctly it loses its sharpness often so fast. Do you know why? Check out the five most common reasons why knives lose their sharpness so fast in the article below:
Why Do Knives Lose Sharpness (So Fast)? 5 Common Reasons
Sharpening A Hollow Grind Knife On Whetstones
If you are not too fussy about slightly changing the profile of the edge on the hollow grind knife, you can use methods other than a wheel to sharpen these blades.
A hollow grind knife can be sharpened on whetstones in the same manner that you would sharpen a normal flat grind knife.
Depending on the curvature of the hollow grind, it may be possible to maintain the curve of the bevel right to the cutting edge, but in most circumstances, this will not be possible.
In this instance, you will slightly change the profile of the edge, and you will be putting a tiny, micro bevel or secondary bevel on the cutting edge of the knife.
While this will affect the slicing ability of the knife and reduce the level to which the edge can be sharpened, the compromise compared to the cost of a professional sharpening may be worthwhile.
The loss of sharpness will be minor, and the edge will still be extremely sharp, but it will not be quite as sharp as the original pure hollow grind.
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Sharpening With Pull Through Sharpeners
Pull through sharpeners normally have a “V” shaped abrasive that is set to a specific angle, and the knife is sharpened by pulling the sharp edge through the V-shaped abrasive.
You can use these tools to sharpen a hollow ground knife, but like using stones, it will put a small secondary bevel on the cutting edge of the knife.
Sharpening A Hollow Edge knife With Electric Knife Sharpeners
Some electric knife sharpeners claim to be able to sharpen hollow ground knives, and you may be lucky and find one that will work on your knife.
In most cases, however, it will be unlikely that the wheels in the electric knife sharpener will be an exact match to the curve that is present in your knife.
Unless you are sure that the curvature of the electric sharpener matches the curvature of the grind on your knife, we don’t recommend that you try these sharpeners on your knife.
4. Sharpen The Knife
The next step to restore the edge of the knife is to use your chosen method and actually sharpen the knife. If you have the equipment, a wheel will produce the finest edge and re-establish the cutting edge while not adding a secondary bevel to the edge of the blade.
Any other knife sharpening methods will also be able to sharpen the edge of a hollow ground knife, but they will change the edge geometry of the knife.
Most knife sharpening systems cater to a double flat grind knife that has a V-shaped cutting edge. Using sharpening methods that are intended for these kinds of knives will create a V-shaped edge on your hollow ground knife.
While there it is certainly not wrong to use these methods, and the knife will become sharp, you just need to be aware that you will be changing the edge geometry of the knife, and it may lose some of its original sharpness.
If you would prefer to not change the edge geometry of the knife, then you will need to have your knife professionally sharpened by someone who has the right tools.
5. Strop The Knife
Once your hollow ground knife has been sharpened, it is always a good idea to finish up by stropping the blade. The sharp edge on a hollow ground knife will benefit from a final strop to make sure the edge is perfectly aligned.
The strop will also polish the cutting edge of the knife close to a mirror finish, which will serve to further enhance the sharpness of the blade.
TIP: Stropping the knife is one of the aspects of knife maintenance that many knife users struggle with in the beginning. The difference between sharpening and honing is one of those areas where confusion reigns. Find out more about this interesting topic in the article below:
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What Knives Have Hollow Grinds?
There is sometimes nomenclature confusion when using the term hollow grind, and some people mistakenly consider a knife that has indentations ground into the blade on each side to be a hollow grind.
This is not a hollow ground knife, but rather a flat ground knife that has scallops ground into the sides of the bevel.
These scallops are to release the surface tension between the blade and the food that is being cut to ease the passage f the blade through the food.
The scallop shape of these indentations has led to these blades being called scalloped blades, but they are essentially flat grind knives with the scallops ground into the bevel. They are certainly not hollow ground knives.
The most common blade that has a hollow grind is the straight razor that many barbers will use to give you a shave.
These blades are extremely sharp because of the hollow ground bevel, and the edge is easily maintained with periodic stropping.
Many old-style skinning knives and even the legendary bowie knives had hollow grinds on the blade. This has changed over time with different sharpening techniques, and the generally accepted best grind for outdoor knives is a flat grind or a slight convex grind.
Knives that are made for hunters as dedicated skinner or game dressing knives will often feature a hollow ground bevel because the knife will have superior sharpness for field dressing the animal.
However, this type of knife would not be used as a general-purpose outdoor knife as the edge is not robust enough for this kind of work.
While hollow grinds are not a new style of griding a knife, it is less popular on modern knives because the edge is more difficult to maintain.
Most knives will have flat or “V” grinds or chisel grinds on the blade. These styles of bevels and edges are much easier to sharpen when sharpening is required.
There are some knives that are produced with a hollow grind, but they are generally purpose-specific blades. Hollow grinds are not considered to be multi-purpose knives because the edge is more fragile than knives with a flat grind.
This is why most general multi-purpose knives such as a bushcraft knife or a chef’s knife will have a flat grind to achieve a more robust cutting edge.
The cutting edge on these knives will not be as sharp as that on a hollow ground knife, but the edge will definitely stand up to more abuse.
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