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Well as i have full time work, and no time to make things at the moment, I've had quite a bit of time to come up with some, perhaps questionable, ideas... I had a go at forging this half a year ago, and everything was looking perfect until i went to quench it. The edge rippled up and it became un-straightenable.

 

IMAG0086.JPG

 

All measurements are in mm.

 

The wedge at the bottom of the picture is a cross section of the blade at it's widest point.

 

The spine tapers from 4mm - 3.2mm and then takes a sharp concave down to 0.8mm until the last 10mm where it starts the final grind angle.

 

The four 10mm sections (two on each side) are the faces that are ground flat on a stone to sharpen.

 

The edge angle is 4.6 degrees.

 

The top and middle picture are the spine and side profile respectively, with the numbered lines between denoting thickness.

 

So my questions are:

 

Is there any way to ht a blade 0.8mm thick with a 4mm spine? clay? edge quench?

 

Is 4.6 degrees too thin for a vegetable knife?

 

And i would love to hear any criticism or thoughts on the practicality of this design!!

 

Thanks for looking

IMAG0086.JPG

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Hey there!!

A couple things...

First, excellent sketches!

 

Second...for my clarification...what is the overall length of the knife (I'm guessing 240mm based off the scale?)...and at what distance from the tip are you looking at hitting the .8mm mark? It looks like approximately 40mm if your drawing is to scale (based off the middle picture, and your 'edge' being 10mm), and if so...that might be a bit too thin for tip durability. I would go no less than .6mm 1cm from the tip...and prefer a bit more in my own knives. As for your edge...the .8mm thick 1cm up from the cutting edge is reasonable. It will work for vegetables or meat, depending on your steel choice, hardening, and temper processes. The edge angle itself isn't an issue. I've gone steeper than that...but past the point you're at here, you've got to be VERY careful or your edge itself will be like tin foil.

Now...as for your hardening this knife the way it's drawn?...that's never going to happen. At least...it would never successfully work in my shop, lol. Your blade profile here is very much like my own preferred profile for chef's knives, and I clay harden with the edge at no less than 1.5mm, and the spine at 2-4mm. This is for a knife that will taper from 3mm or so over the heel, to 1.8mm mid blade...and a sharp taper to the tip. Any less and the warpage is usually significant. This will depend somewhat on your steel choice (again) and quenchant (I use W2 and Parks 50 or brine). Forging in the profile and some of the bevels will work, but the remainder of the knife would need to be ground in. This is just something that comes with making ultra thin knives.

Overall, your profile is nice. Like I said...it's almost a mirror image of my own chosen profile. If you like I will post a picture of an example that mirrors this one almost perfectly lol. If not, that's more than fine...I don't want to clutter your thread with my work!! Also, one thing I would do for practicality is raise the tip about 6-8mm or so...and bring the last 1/3 of the edge up to meet it. This gives you 2/3 of the edge as a flat...which is more than sufficient...and a nicely profiled tip for more fine work. This will also help strengthen the tip some by reducing the angle of the profile.

 

On the practicality of the grind and bevels themselves...a hollow grind through the middle of the blade is surprisingly common in high end chef's knives, though most people don't realize it. I do it myself often. What diameter wheel are you planning to use to grind the hollow in? With a 50mm heel, it will need to be rather large.

Anyway, if you have any other questions I'm more than happy to help. I make my living doing mostly Japanese style chef's knives...so I'm in a unique position to help you out I think :).

Edited by C.Anderson
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  • 3 months later...

Hey Anderson,

 

Thanks for the great response. After reading your post a few times, I think you've confirmed my suspicions that it's a bit of a ridiculous design, and probably not worth the trouble of trying to make again. Having thought about it some more, i think it would have minimal, if any, advantage over a more typical geometry. Plus the finished knife would probably only be suited to vegetables and other soft ingredients, so would be better off not reinventing a square wheel, and just making something along the lines of a nakiri.

 

Your comments on tapers, thicknesses before quench, and more curve in the tip are really helpful. I plan on doing alot more kitchen knives, so your advice will used.

 

Apologies for the slow reply, I have not been able to log on the last few months due to forgetting my password and troubles will the email reset at my end. Thanks again

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