2 Swedish Air Force survival knives

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kwakster
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2 Swedish Air Force survival knives

#1

Post by kwakster »

Recently acquired these two fixed blades made by Swedish manufacturer Pontus Holmberg.
According to this website the model was once used as a survival knife for the Swedish Air Force: http://www.gotavapen.se/gota/artiklar/k ... rvival.htm

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I'm in the process of giving each one a bit of TLC, and will post some pics later on.
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Re: 2 Swedish Air Force survival knives

#2

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Blade hand reground to it's original full convex blade shape on a Foss 7205 black/green silicon carbide stone used with oil, then refined on 400 grit and 1000 grit SiC wet & dry paper used with oil on glass, and the tiny burr stropped off on hard cardboard with 1.0 micron diamond paste.
The new apex measures between 20 and 22,5 degrees inclusive.
Very hard (guesstimate 64-65 HRC) and also very wear resistant steel.
Handle reassembled, now with all washers glued and pommel repolished, then treated to a few coats of warm Granger's wax.
Sheath waxed and hand restitched.

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Re: 2 Swedish Air Force survival knives

#3

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The second knife is a bit worse, also due to the handle's leather midsection which had rotted over time together with a pommel stuck in place.

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Re: 2 Swedish Air Force survival knives

#4

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Both Pontus Holmberg knives are made from iron ore from the Dannemora mine, which resulted in very pure steel due to it being rich in manganese.
In earlier centuries it was known as "oregrounds iron": https://en.wikipedia.org/wiki/Oregrounds_iron
However i don't know if that name was still being used by the time these knives were made in the late '40's or early '50's of the 20th century.

Sheffield also used a lot of this same ore to make their famous crucible cast steel from ~1740 up until ~1960.
These two Swedish knives however are noticeably harder as well as much more wear resistant when compared to the vintage English crucible steel knives that i've hand reground/sharpened over the years.
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Re: 2 Swedish Air Force survival knives

#5

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Currently busy with making a new leather midsection for the handle of knife # 2:

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Re: 2 Swedish Air Force survival knives

#6

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The new leather midsection after rough machine sanding with a cheap Parkside linisher (which i modified so it can do slack belt sanding):

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Re: 2 Swedish Air Force survival knives

#7

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Busy fine sanding the handle surface:

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Re: 2 Swedish Air Force survival knives

#8

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The blade has been hand reground on the Foss 7205 combination stone (burr is partly visible), and a few refining steps on wet & dry SiC paper will follow later.
Now regrinding the swedge with 300 and 600 grit diamond files.

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Re: 2 Swedish Air Force survival knives

#9

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Regrinding the old jimping / notching using a cordless drill with diamond bit & WD40 oil:

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Re: 2 Swedish Air Force survival knives

#10

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How the blade looks after hand regrinding to full convex again on the green silicon carbide side of the Foss combination stone used with WD40 oil.
The new edge angle measures ~20 degrees inclusive.

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Re: 2 Swedish Air Force survival knives

#11

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Currently experimenting a bit with different grits of diamond paste on thin cardboard to see what gives both a nice blade finish as well as a good apex.

Already found that only removing the burr is not enough to get the sharpest of edges on this steel, i have to continue stropping a bit to also get the (presumed tungsten) carbides into the right shape.
I also have to tinker some more with the appearance of the blade finish (now it's a bit too shiny for my taste), but the current apex is reverse hairwhittling sharp (chest hair) @ ~20 degrees inclusive.

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Re: 2 Swedish Air Force survival knives

#12

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While busy with finetuning the handle the knife slipped out of my rubber coated vise and fell from a measured hight of 1.10 meter on one of the concrete sidewalk tiles which form the floor on my balcony, and landed on the belly part of the edge.
I did not try to catch the falling knife :-)

To my surprise there was only slight denting in that area, no large chips, which i would have expected given the presumed high hardness in combination with the narrow edge angle.
Anyway, due to this i had to regrind the blade again on the green silicon carbide side of my Foss 7205 stone, and that is where i am now.

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Re: 2 Swedish Air Force survival knives

#13

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The result:

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Re: 2 Swedish Air Force survival knives

#14

Post by Enactive »

Beautiful work. Thanks for sharing.
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Re: 2 Swedish Air Force survival knives

#15

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Very nice work and thanks for sharing the process.
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Re: 2 Swedish Air Force survival knives

#16

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Spectacular work! Thank you for the series of posts and great pictures.
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Re: 2 Swedish Air Force survival knives

#17

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Wow. Great thread, great work and great skills.
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Re: 2 Swedish Air Force survival knives

#18

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Thanks for taking us along the journey. Those turned out really nice.
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Re: 2 Swedish Air Force survival knives

#19

Post by Manixguy@1994 »

I am in awe ! Thanks for sharing your hard work , results are beautiful. MG2
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Re: 2 Swedish Air Force survival knives

#20

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At this point i'm quite certain that the steel in these 2 knives is an entirely different type when compared to the standard Sheffield made crucible cast steel.
One reason is that Pontus Holmberg classifies it as a stainless steel, where the Sheffield made crucible cast steel was a carbon steel.
See this detail picture of the sheath of knife #2, and "Rostfri" is the Swedish word for stainless.

https://ibb.co/bzfSNhV

The second reason is the very high wear resistance of this Swedish steel: using whatever grit of black silicon carbide on it is extremely slow, be it waterproof SiC paper or the coarse black SiC side of the Foss 7205 combination stone.
The green silicon carbide side of that stone however, even though much finer than the black side, cuts the steel noticeably faster, better, and also with great feedback.
Based on this i'm beginning to suspect there might be quite a lot of tungsten carbides in it, also because the steel is able to take & hold a thin ~20 degree inclusive edge angle while whittling an old piece of hard beechwood cutting board (tested with knife #1)

A possible third reason is a little piece of info i found on this website with mining data: https://www.mindat.org/loc-3153.html
According to this there could be (traces of) silver in the Dannemora iron ore, which made me remember what Faraday wrote about the alloy of steel with silver in this thread: https://www.bladeforums.com/threads/phi ... t-20358902
Problems might be that Faraday wrote about his findings around 1822, he doesn't talk about silver in ore but about lab made alloys, and i'm no metallurgist.

Maybe Larrin can tell us more about the validity of Faraday's claims about steel alloyed with silver, and maybe his thoughts about the type of steel in these two Swedish knives.
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