# Where should my knife balance? (WITH CAD)



## ForeverLearning (Mar 15, 2019)

So I am mocking up my 3rd/4th knife design in CAD. I have applied carbon steel for the blade and oak as handle material. 


One issue I am uncertain of is the balance point of a knife, I am aiming to produce a 6" knife, currently the balance point is by the heel of the blade (shown below by the pink coordinate system):







Secondly, the mass is roughly 114g, is this what you would expect of a 6" chef's knife? 
Cheers for any suggestions. I have not included a taper from handle to tip on the blade, if the mass is large I could incorporate that then it would be reduced. (i'll also try to find details on the exact wood/steel i'll be using and use custom materials in Solidworks).


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## ForeverLearning (Mar 15, 2019)

To add, I adjusted materials to match O1 Tool Steel and Cherry wood which is what I will be using (1" of African Blackwood will be used, this is 2x as dense as cherry 1270kgm^-3)

Accounting for this the mass will be 118g+7.5g, so overall approximately 125g for the knife with handle. The balance point has also moved closer to the handle. 





What are your opinions on the mass and balance of this design? 

Cheers, 
L


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## milkbaby (Mar 15, 2019)

It's down to personal taste in my opinion. General consensus tends to state that knives should have relatively neutral balance with the balance point somewhere from around the top of the handle to the pinch grip point. But preferences can vary, European knives sometimes have that heavy full metal bolster which makes a knife very handle heavy. That can feel advantageous when the user keeps the tip on the board and cuts in a rock chopping motion.

Keep in mind wood density can vary as trees can grow under varying conditions which will affect that property. You can adjust the balance by adjusting the size of the actual handle when made.


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## MowgFace (Mar 15, 2019)

I agree with Milkbaby that it largely falls to personal preferences. I tend to like blade heavy knives, with the balance point in front of the heel. YMMV


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## HRC_64 (Mar 15, 2019)

there are two different isssues -- the balance point, and the moment of inertia


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## HRC_64 (Mar 15, 2019)

Also consider distal taper -- which impacts all of the above 
not to mention performance of the grind when in use.


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## ForeverLearning (Mar 15, 2019)

@HRC_64 could you elaborate on moment of inertia?


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## ForeverLearning (Mar 15, 2019)

Is a distal taper a must in a knife design?

I think I want to make this knife left handed too as it will be for me. So I will grind the right hand side 90/10? I need to look in to this more


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## merlijny2k (Mar 15, 2019)

The bolster doesn't affect balance much since it is almost at the balance point. It's the endplates and unnecessarily thick tangs that mess the balance up. Problem isn't even with the bigger euro chefs, problem is they use generic handles on blades that are too small and light for them. Renders most expensive euro parers awfull to work with.

What feels rigt is often a balance point in front of but very close to where you pinch grip. I prefer 2-3mm close. The deeper the pinch the lighter the handle should be. Right at the heel works well for me.

As for moment of inertia: If you add mass at the back you need less of it to balance the knife, giving a lighter knife overall. Less tiring to work for long time. A bolster adds a lot of mass in an ineffective place. You need a big one to affect balance. A heavy knife has the weight behind the cut helping it get through, but it is less fast and strains the arm more.

Having a part of heavier wood to the front should not affect performane that much.

Nice CAD drawings by the way. It gets a lot more confusing once you start to draw taper.


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## HRC_64 (Mar 15, 2019)

ForeverLearning said:


> @HRC_64 could you elaborate on moment of inertia?



imagine the 'balance' of a barbell vs a compass needle...


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## WildBoar (Mar 15, 2019)

In my opinion the shorter the knife the less important the balance point location. A 6 inch knife is pretty short. If you want to move the balance point forward, increase the machi. But for a knife that short I probably would not care.


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## milkbaby (Mar 15, 2019)

WildBoar said:


> In my opinion the shorter the knife the less important the balance point location. A 6 inch knife is pretty short. If you want to move the balance point forward, increase the machi. But for a knife that short I probably would not care.



I was gonna comment on moment of inertia but agree with David in the case of a 6" knife. The shorter the knife is, the less important balance is in my opinion. You're not waving around a tip that is 8, 9, or 10" out from the handle with a shorter knife.


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## ForeverLearning (Mar 15, 2019)

@merlijny2k are distal tapers not continuos lines from heel to tip? If so I don't see how it could be an issue mocking up on CAD


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## WildBoar (Mar 15, 2019)

ForeverLearning said:


> @merlijny2k are distal tapers not continuos lines from heel to tip? If so I don't see how it could be an issue mocking up on CAD


Not always. Some makers leave them constant width for a little bit, and then start the taper to the top. I doubt any 2 makers do it exactly the same way.


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## merlijny2k (Mar 17, 2019)

ForeverLearning said:


> @merlijny2k are distal tapers not continuos lines from heel to tip? If so I don't see how it could be an issue mocking up on CAD



Even if it is a straight from heel to tip, I find quite complicated to draw a tapered knife in 3d without the bevel getting shallow toward the tip. There is probably a good solution but I don't know how to do it.


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## Nemo (Mar 17, 2019)

merlijny2k said:


> Even if it is a straight from heel to tip, I find quite complicated to draw a tapered knife in 3d without the bevel getting shallow toward the tip. There is probably a good solution but I don't know how to do it.


I recall that @Kippington showed very eloquently that it's only possible by continuously varying the angle of the bevel as you move along the taper:

https://www.kitchenknifeforums.com/threads/commission-wip.34734/

This is why there tends to be less (or nil) taper on kurochi and many wide bevel knives. At least until the wide bevel meets the spine (near the tip). It also affects damascus knives, as you will be grinding through the layers at a different angle, producing a different patttern as you move down the blade.


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## ForeverLearning (Mar 17, 2019)

My next knife is going to be made from 2mm O1, I'm tempted to leave the distal taper. I'm very inexperienced and think focusing on a consistent primary bevel should be my focus. 

If I grind a bevel at a constant angle it could end up tapering the end anyways right?


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## milkbaby (Mar 17, 2019)

There is nothing special about grinding the shinogi at a consistent distance from the edge whether distal tapered or not other than doing it freehand and checking your work frequently. The angle will take care of itself as you watch where the grinding is taking place along the blade. If you're going to mill it out by computer control, I assume the software should be able to calculate everything itself and if not that seems like not great software to use.

I understand a very even bevel is liked by some users as it makes getting a nice looking finish easy when thinning. But I actually feel an irregular surface is more beneficial for general purpose chef's knives for improved food separation and food release. Look at the forged geometry knives where only a short grind is done at the edge by Takeda hamono, Bryan Raquin, and Will Catcheside among others.


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## ForeverLearning (Mar 18, 2019)

I follow Raquin, I will definitely check the other makers. 

I think I'll grind the primary bevel in with my jig, then freehand a taper. 

From my understanding in the link to Kippingtons thread if I grind the taper then do the bevels I'd have to free hand for a consistent bevel height.


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## milkbaby (Mar 18, 2019)

As Nemo mentioned, if you want the shinogi a consistent distance from the edge, then the bevel angle needs to narrow as the blade tapers narrower towards the tip. If you still want a "cosmetic" shinogi after grinding in the bevel at a set angle with a jig and adding the distal taper, then you can polish below the "shinogi" in a different way from above the "shinogi". Obviously, that would no longer similiar to your CAD drawing any more.


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## merlijny2k (Mar 19, 2019)

All very good and valid points albeit they leave open the question of how best to model the resulting complex doubly curved surface into a CAD model for the purpose of calculating the balance point prior to actually making the knife.

The freehand procedure as described is not that hard. I did it once and it worked just fine except my clumsy and inexperienced office dwellers hands produced f&f that leaves much to be improved.


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## ForeverLearning (Mar 19, 2019)

@merlijny2k we should be able to find a solution. 

I sketched along the top plane (spine) of the knife and extruded cut down through the blade, this resulted in an inconsistent bevel. 

I'll try again and try to figure out a solution.


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## Nikabrik (Mar 19, 2019)

I did a model of a knife remarkably similar to yours a free months ago; I handled it by using surfaces. You can extrude the blade profile, then trim away outside the distal taper. Trim the side faces at the shinogi line to form the hira. Now trim the edge face to whatever width you want behind the edge (eg, 0.005"). You can then do a lofted surface from the shinogi line to the edge. Next, knit surfaces and chamfer the edge if desired.


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