Ergonomics and Knife Balance

Ergonomics and Knife Balance

Posted by John Alexander Co on 20th Nov 2019

“What makes this knife different to that one?”

It’s a question on everyone’s mind when choosing between knives that would serve the same purpose in the kitchen. Two knives might seem practically indistinguishable especially to a first-time buyer, and it’s honestly difficult when you don’t particularly know what might set them apart from each other. If that’s you, hopefully this post might be able to introduce you to a very important consideration when comparing knives - balance.

 

My Experiences with Cooking

I’ve had my Kurosaki gyuto at home for over a year and a half now and have used it in every sort of way from julienning and mincing vegetables to trimming and portioning whole cuts of meat, breaking down poultry, and even filleting fish. It’s a great all-purpose knife that has served me well, and it continues to be my go-to knife for most kitchen tasks.

Left: My Kurosaki Gyuto (April 2018), Right: A whole salmon I filleted with my Kurosaki

  

Recently however, I brought home a Tanaka gyuto to test out over the weekend. Wanting to take full advantage of the time I had with it, I decided to make kimchi over a Sunday morning. This involves a laborious process of chopping vegetables such as carrots, daikon, onions, spring onions, and quite a bit of garlic in order to make the spicy paste, so this trial tested the Tanaka’s functionality and comfort over an extended period of prep work.

  

The Tanaka Gyuto I Tested Out at Home

  

In times when I’ve used my Kurosaki over similar durations, I had found my palm near my pinky finger quite tired and fatigued. Meanwhile, I noticed how the Tanaka had handled all of the vegetables without making me feel the slightest bit tired. Somehow, the Tanaka felt lighter in my hand than the Kurosaki, though I couldn’t exactly tell why that was the case. Heading back to the K&S showroom, I set out to investigate their differences.

For the comparison, I used the same Tanaka Ginsan 240 mm gyuto that I had brought home for testing and a Kurosaki R2 240 mm gyuto that was on display in the showroom.

 

Weighing the Knives

Firstly, I needed to confirm whether or not the Tanaka was physically lighter than the Kurosaki. Weighing the two knives, the Tanaka was 185 g, while the Kurosaki was actually lighter at 184 g. This confirmed that the perceived lightness of the Tanaka did not have to do with physical weight, but it was instead a function of ergonomics and knife balance.

Left: Tanaka Weighing 185 g, Right: Kurosaki Weighing 184 g

 

Ergonomics

Ergonomics has to do with the quality of a design that ensures comfort and ease of use of a product. For knives, it includes how comfortable a knife feels to hold, and one major factor of this is its balance. Two factors play into this – the location of a particular knife’s balance axis and the pivot point caused by your grip style.

 

Balance Axis

The balance axis is a line that you can draw on the knife that, when placed on an elevated edge, will keep it perfectly horizontal without tipping. The further along the blade the balance axis is, the more blade-heavy a knife will be, and in some situations like for a Wa petty knife, they can also be handle-heavy.

Examining both knives more closely then, the balance axis of each knife was found by adjusting its position on an edge until it balanced horizontally without tipping. The results from this test were clear. The Kurosaki’s balance axis was considerably further along the blade, while the Tanaka’s balance axis was much closer to the heel. 

Kurosaki's Balance Axis

Tanaka's Balance Axis

 

Pivot Point

Aside from finding the balance axis, another important consideration for balance is the pivot point, which is the point which a knife will tend to rotate around. Practically when using a knife, this would be a point right by the heel or on the handle where your finger is supporting a vast majority of its weight. Using a pinch grip for the Wa handle knives in particular, it tends to be at the transition from the blade to the tang.

Pinch Grip & Pivot Point Kurosaki (Left), Pinch Grip & Pivot Point Tanaka (Right)

 

Overall Knife Balance

Now, we put these two concepts of balance axis and pivot point together. Knowing where the balance axis of a given knife is, having a pivot point anywhere aside from its balance axis means that a knife will have a natural tendency to rotate along the heavier side. The fact that any grip will position the pivot point more towards the handle means that most Wa handled knives will feel blade-heavy. Knives with a balance axis further along the blade will exert a greater force that needs to be counteracted by your hand.

Now going back to the Kurosaki and Tanaka, putting them on the exact same scale of measurement, the balance axes and pivot points of each knife are shown in the annotated blade profiles. The distance between the pivot point and balance axes were measured, and while the Tanaka’s balance axis was only about 1.67 cm away from the pivot point created by a pinch grip, the Kurosaki’s measured at 3.66 cm, which makes the Kurosaki significantly more blade-heavy. 

 

Annotated Measurements for the Kurosaki and Tanaka

For someone like me who uses a relatively loose pinch grip, a standard octagonal handle concentrates the required counteracting force at the area of your palm near the pinky finger. Combined with a push cutting style that repeatedly lifts the knife off the chopping board, this means my hand undergoes repeated stress cycles while doing cutting tasks – a similar feeling to being pinched in the same spot a couple of hundred times in a row. No wonder the Tanaka felt so much more comfortable to use for me!

 

Final Words

With all that being said, a more balanced knife may not always be the preferred choice for everyone. There are instances where a blade-heavy knife may suit you better. For example, if you tend to have a tighter grip, you could evenly distribute the counteracting force through your palm while benefitting from exerting less force for the same cutting tasks!

At the end of the day, choosing a knife based on balance is all about knowing your preferred cutting style and grip. If, however, you’re not quite sure about all that just yet, you certainly can’t go wrong with choosing a more balanced knife.

Thanks for reading, and hopefully this post has broadened your knowledge on knives!

 

About the Author

John is a final year Mechanical Engineering student at the University of New South Wales currently doing an internship at Knives and Stones. He has a strong interest in cooking, which eventually led down to the very deep rabbit hole that is Japanese knives and knife sharpening. Now, as both an enthusiast and an engineering student with an unlimited access to the Knives and Stones showroom, he gets to play around with knives all day to study them carefully for your benefit.