/diy/ - Do It Yourself » Thread #894807

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Blade design

Anonymous Wed 28 Oct 2015 20:53:50 No.894807 View Reply Report Delete

Quoted By:

I'm looking for info on blade design. Specifically, is there any math, or generally accepted knowledge out there on the best ratio of length to width for a general use knife blade?

"hey anon, what the hell are you on about?"
Lets say I'm grinding a knife blade out of an old file. I am limited to the width of the file "blank" for lack of tools, and I'm pretty much left with the variables of "point" and "length", right? If I want this to be a useful utility knife, how do I decide on the best length?

How much straight, flat belly between the sweep up to the point and the hilt is TOO much?

I understand that every knife is a tool for a purpose and the purpose should dictate the design, I'm just looking to learn something new, if you all have any thoughts on the matter.

Anonymous

Anonymous Wed 28 Oct 2015 21:14:37 No.894825 Report Delete

Quoted By: >>894827

I would try /k/ and /out/. They may be able to answer you better regarding blade design.

Anonymous

Anonymous Wed 28 Oct 2015 21:15:41 No.894827 Report Delete

Quoted By:

>>894825

Oh, and /out/ usually has a Knife/Blade general. They hate when people make new knife threads, so be sure to ask there.

Anonymous

Anonymous Wed 28 Oct 2015 21:33:38 No.894836 Report Delete

Quoted By:

I found that 1.5 by 5-6 inches usually works best for me when making utility knives.

Anonymous

Anonymous Wed 28 Oct 2015 21:38:39 No.894839 Report Delete

Quoted By:

There's not really any design or formula to the blade shape. It varies based on what it will be used for, the material it was made out, and just plain old what looks good. Unless you use knives yourself and have strong feelings about blade design, just go with some kind of traditional shape.

Now, if you're talking about design of the cutting edge, that's different, but information on different edge angles and shapes is pretty easy to find on google.

Anonymous

Anonymous Thu 29 Oct 2015 00:20:15 No.894906 Report Delete

Quoted By: >>894911

/out/ here, there isn't any sort of important length to blade width ratio. Depending on what you use it for though, the thickness of the blade is very important, as it makes the knife a lot more robust. There is a huge variety to grinds you can do too, I personally prefer Scandinavian or sabre grinds.

Also, as a metallurgy student, I have to tell you that whatever you make isn't going to hold an edge well unless you forge and properly heat treat it. Grinding stuff down probably won't cut it.

Anonymous

Anonymous Thu 29 Oct 2015 00:49:24 No.894911 Report Delete

Quoted By: >>894931

>>894906
>I have to tell you that whatever you make isn't going to hold an edge well unless you forge and properly heat treat it. Grinding stuff down probably won't cut it.

and as a professional bladesmith, I can tell you, that this guy is wrong. He's talking complete bullshit.

You can grind your blade, you can forge it, you can CNC mill it, you can shape it by whatever method you like. Hell, use your teeth and gnaw it to shape. It will make absolutely _no_ difference to the edge-holding qualities of the finished product.

The only thing that determines edge-holding is the heat-treatment of the steel being done properly.

How you shape it prior to heat-treatment is absolutely irrelevant to the quality of a blade. In fact, forging is more likely to result in you introducing carburisation of the steel from overheating, or irregularities in the steel due to strikes as it cooled too far, when compared to stock removal. Remember, to become barstock for forging or stock removal, the steel has already been shaped from a 1-10 tonne ingot through 20 sets of rollers pushing a thousand tonnes of pressure per square inch through the metal.

A good quality heat-treatment, for the correct alloy, with 2-3 normalisation cycles after shaping, followed by a quench in a suitable quenchant for the steel alloy chosen (ie, for 1095, go for Parks' 55 quench oil.), followed by 2-3 heat-treat cycles of around 200-220 degrees C, will result in a blade of around 57-59HrC hardness which is both durable against cracking, and will have exceptional edge-holding properties.

I will repeat: what method you use to shape the blade has absolutely NO bearing on the quality of the edge holding properties of the knife. Only the choice of steel, and the application of a proper (or improper) heat-treatment will determine the edge-holding quality of the blade.

Anonymous

Anonymous Thu 29 Oct 2015 02:04:26 No.894931 Report Delete

Quoted By: >>895012

>>894911
>what is reading comprehension

Anonymous

Anonymous Thu 29 Oct 2015 09:13:25 No.895012 Report Delete

Quoted By:

>>894931
>what is reading comprehension

its the abiilty to read a phrase like " isn't going to hold an edge well unless you forge and properly heat treat it. Grinding stuff down probably won't cut it." and knowing that its bullshit, and that by making claims that you can only forge, and that "grinding stuff probably wont cut it" that twat is being entirely misleading, and promotes ignorance.

I suggest you learn what you're talking about.

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