Blade Length

[Rajat]

http://www.britishblades.com/forums/sho ... ot-all-bad

for knife which cost $325 that is real horrible report. nice design but steel and hardening chosen seems to be wrong

So your search of the Extrema Kukri finally led you to this review. I had seen it some time back too.

Do not get so discouraged, of course there might be a few problems in using it like an axe or a machete + you never know if it was the competition who posted this picture!

[Subal das]

http://www.britishblades.com/forums/sho ... ot-all-bad

for knife which cost $325 that is real horrible report. nice design but steel and hardening chosen seems to be wrong

So your search of the Extrema Kukri finally led you to this review. I had seen it some time back too.

Do not get so discouraged, of course there might be a few problems in using it like an axe or a machete + you never know if it was the competition who posted this picture!

I'm a member there for few years, this guy who posted Extrema Ratio - Beware, not looks like competitor for Extrima but rather quite ordinary Brit.

just checked Extrima kukri hardened up to 54HRC, should not be so brittle. maybe also problem with design, if blade is too thin at the edge it can broke.

[Rajat]

54 HRC seems to be ideal for this as it is a large blade for hacking etc.

If what we see is correct there is something wrong with it. If the blade is too thin it should "roll" and not chip off like what we see here.

[Subal das]

54 HRC seems to be ideal for this as it is a large blade for hacking etc.

If what we see is correct there is something wrong with it. If the blade is too thin it should "roll" and not chip off like what we see here.

yes good point, there is some thing wrong with it

[abhrankash]

54 HRC seems to be ideal for this as it is a large blade for hacking etc.

If what we see is correct there is something wrong with it. If the blade is too thin it should "roll" and not chip off like what we see here.

yes good point, there is some thing wrong with it

Dear Sir,
This is due to the formation of toorosite during the hardening process on a wrong steel and the cross section at that point may not be good enough to sustained the cutting pressure that's why it has got chipped off.

So, from this we can say that the furnace used may not be good enough to control the even distribution of heat.
and the second reason may be the negligence in manufacturing process which results a very weaker section at the edge of the blade.
That results chipping at the edge of the blade.

[abhrankash]

[quote="Subal das"][quote="Rajat"]54 HRC seems to be ideal for this as it is a large blade for hacking etc.

If what we see is correct there is something wrong with it. If the blade is too thin it should "roll" and not chip off like what we see here.[/quote]

yes good point, there is some thing wrong with it[/quote]


Dear sir,

Here is your blade design.
valuable and more suggestion will be an added advantage to the design blade thickness is 6mm and 11mm in mid section full blade length is 347mm,The smoothness test of edge and the surface of blade report attached.
============================================================
Information listing created by : aocss
Date : 12/14/2010 10:18:54 AM
Current work part : D:\Das\O-RINGS\khukri.prt
Node name : lambro
============================================================
Info Analysis - Examine Geometry
Tiny Objects - Tolerance = 0.025400000
No tiny objects found
------------------------------------------------------------
Misaligned Objects
No misaligned objects found
------------------------------------------------------------
Face Smoothness
Faces passed smoothness check
------------------------------------------------------------
Date : 12/14/2010 10:22:48 AM
Current work part : D:\Das\O-RINGS\khukri.prt
Node name : lambro
============================================================
[b]Measurement Mass Properties[/b]

Displayed Mass Property Values
Volume = 118812.619902171 mm^3
Area = 36276.703062411 mm^2
Mass = 0.930378854 kg
Weight = 9.123908019 N
Radius of Gyration = 85.354579556 mm
Centroid = 37.532354010, 0.000038034, 164.794867416 mm

[b]Error Estimates[/b]

Volume = 300.138418936
Area = 32.771359517
Mass = 0.002350276
Moments of Inertia (Spherical) = 1.139525172
Center of Mass = 1.151079709, 1.062868411, 1.450181729
Moments of Inertia (WCS) = 488.861829388, 571.956429795, 157.818760795
Products of Inertia (WCS) = 31.198509170, 104.064796253, 158.493475112

[Subal das]

that is very nice model indeed

most knife mares using simple 2D patterns

how this model can be used to make knife, is it only can be made on CNC machine or by some traditional method also

[Rajat]

Good question Subal

[Subal das]

abhrankash, after making such nice model you are on half way to start making real knives actually.

[abhrankash]

abhrankash, after making such nice model you are on half way to start making real knives actually.

Dear sir,
By using this model you can get it done by CNC machining only or you can use the 2d drawing to check the accuracy of traditional manufacturing process.well I do work in a tool room where we are having 2 nos. of CNC milling machines but as I have stated earlier rest of the things are to be done by hand only.
I hope you are satisfied with the model. and with the mass properties also.
Kindly take a note of the other details which I have provided you with.

[Subal das]

but on model only blade not the whole knife with handle



so can you make such knife in free time, PM me if you can or send SMS

also weight of Extrima kukri g 585 what weight you have calculated I'm not getting it, also weight may depend on steel, D2 will be more heavy for example, then C30V.

and on your model thickest point 11mm, but on Extrima BLADE THICKNESS (MAIN BLADE): mm 6,3.
11 mm thickness that will be in excess for such blade
Extrima kukri seems to be flat in profile

one thing i would change is reduce grinding space in this place, that will increase angle and prevent such damage which we have seen posted on britishblades



also grinding profiles on your model does not look the same as on Extrima

[abhrankash]

but on model only blade not the whole knife with handle

[ Image ]

so can you make such knife in free time, PM me if you can or send SMS

also weight of Extrima kukri g 585 what weight you have calculated I'm not getting it, also weight may depend on steel, D2 will be more heavy for example, then C30V.

and on your model thickest point 11mm, but on Extrima BLADE THICKNESS (MAIN BLADE): mm 6,3.
11 mm thickness that will be in excess for such blade
Extrima kukri seems to be flat in profile

one thing i would change is reduce grinding space in this place, that will increase angle and prevent such damage which we have seen posted on britishblades



[ Image ]

Dear sir,
This is the only thing that I have tried to do, but the weight is around 0.937Kg in the case of British Blade design they have tried to reduce weight by providing recess on the edge and this make the cross section much thinner and the blade get chipped off.
But in case of my design this things won't happens as you can see in the posted Images and this kind of designs are easy to grind and resharpen the blade without any kind of special attachments and also no highly trained professionals are required.

This kind of blade can be resharpened by the use of kerosene oil and polishing stone no 1200-1400 (girth no) color of stone will be YELLOW and this kind of stones are readily available in market (any shop selling polishing or tool-room equipments) if not possible contact me I will send you by courier.

[Subal das]

thanks I no need stone, as I do not making knives, I would like to but no opportunity at present. for sharpening I'm using DMT diamond stones which are rest forever and really best I even seen.

-- Wed Dec 15, 2010 4:42 pm --

can you say what edge angle will be on your model and on extrima kurki with modification I proposed

[abhrankash]

thanks I no need stone, as I do not making knives, I would like to but no opportunity at present. for sharpening I'm using DMT diamond stones which are rest forever and really best I even seen.

-- Wed Dec 15, 2010 4:42 pm --

can you say what edge angle will be on your model and on extrima kurki with modification I proposed

Dear sir,
I have completed the 3D design of the required blade now I will be posting the same to your mail Id,
and just give me 2 days more so that I can provide you with the 2D design,with which you can check the accuracy of the curve and the other things as well which are main feature this traditional weapon. If you want to manufacture by any traditional method also.

And about the handle that you have to make out of wood or if you are having and spare plastic handle to fit with you have to give me the center distance of the hole in both the direction of X and Y as well.

If you want to have a good handle then you should go for wooden carved handles.
or the handle made out of horn of buffalo.(horn work of ORISSA).

Now coming to the design point of view the design of the extrema is such that it produces much thin sections at many places which results chipping of the blade edges at different places as product designer I would like to suggest you that you should go for the original design of this traditional weapon.

The feature that they have added to by cutting the extra steel is just to reduce the weight but they did not considered about the strength of the blade during the work process and the working conditions.There is no doubt that they might have used the best grade of the steel but there are many things that decides the durability of the blade except the grade of the steel that is being used.

[Subal das]

thanks you very much for your time and efforts, you are absolutely right design of this blade are seriously flown, it look flashy, but when it come to work it simply do not perform.

I would suggest to leave it is as it is for Extrima to improve and wait for Katana or some other members to come with traditional kukris.

I read some bad reviews about handle also and I agree for such blade handle is unappropriated.

that handle much better