Recommendation? Tommi Puukko Grind Angles?

DeadFall27

DeadFall27

Joined
May 18, 2011
Messages
1,476
Hey all,

For those of you who make Tommi Puukkos, what angles do you grind your main bevels and top swedge? (I do not know the proper nomenclature for the rhombic top grind, I apologize)

I bought a grinding jig so I can stop ruining steel (Ive ruined 5 blades so far attempting freehand), and was wondering what to set them to.

EDIT: I am using 1/8" stock
 
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Except thickness , height / width of blade is also required so someone can calculates angles :)
But you don t need them to know .Mark center line on edge and spine .Draw line how high you want to be main bevel.Then first grind in narrow angle to close match center line on edge from both side .Then start to change angle that way that you grind towards line you draw as end of main bevel grind .For other side use jig as it was set for last grind on first side and grind till you reach upper line .That is it ....... do same for top grind .Angle depends of that how thick you want to be spine after grinding...
On drawing blue line is first grind you make from both side ....
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I like Natlek's approach
To answer the question: I think those blades look best with a bevel 2/3 to 3/4 of the way up the blade. With say a 30mm high blade, 3mm thick that's tan-1((3/2)/(2/3*30)), uhhh *counts fingers*, ~4.5 degrees
Seems a bit low, for a Scandinavian grind. I would have thought 10 degrees would be a better starting point, maybe more.
 
Im going to be making 1/8" thick stock, ~20m-28m wide blades. Mostly 25mm. I'll try out the 10 degree grind and report back. Thank you so much for your help!

I asked a puukko enthusiast group and a member said they like to use 10 degrees (20 inclusive) as well and wanted to get a second opinion! And I have actually found out the hard way that 4.5 degrees is way too shallow..I ruined my last blade trying to do that.
 
I did some calculations and this is what I ended up on:
If you are using 3,175mm(1/8'') thick steel and the blade is 25mm(0.98'') wide and you want to get the cutting bewel to take 3/4 of the blades width, you would have to grind the cutting bevel at ~4,8°. You will get a spine thickness of 2.8mm(0,11'') if you grind the spine bevel at ~25.5°.

How thick do you want to leave the spine? I personally don't make any of my puukkos spines less than 2.8mm(0,11'') because it's starts to look too thin for a puukko. At least for my eyes.
 
People confuse the edge angle with the bevel angle. Very few blades have a bevel angle of more than 7°. On a blade the size of a puukko, the bevel will be less than 5°. Once fully ground, the edge is applied with a micro-bevel.

I always advise to NOT try and shoot for an exact angle with a jig. Just file/grind the bevels to the geometry you want. If you want a 18mm bevel height on a 25mm blade, then make the bevels that high and you are done. The angle will form itself. All you need to do is keep an eye on the bevel as it walks up the side and not let it pass the centerline on the edge or go above the place you marked where the bevel will stop.
 
DeadFall27 said:
Im going to be making 1/8" thick stock, ~20m-28m wide blades. Mostly 25mm. I'll try out the 10 degree grind and report back. Thank you so much for your help!

I asked a puukko enthusiast group and a member said they like to use 10 degrees (20 inclusive) as well and wanted to get a second opinion! And I have actually found out the hard way that 4.5 degrees is way too shallow..I ruined my last blade trying to do that.
Click to expand...
If you try to grind main bevel on 10 degree , your report would be that you ruined another blade . . . AGAIN :D Do as I say to you end make that knife .......:thumbsup:
Wait a moment . . . .HOW you measure that 4.5 degree grinding angle ????
This is my first ever grind Puukko blade ...with jig of course , and I have no idea which angle I use ..............
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As stated above, mark the height where you want the bevel to stop. Then grind the edge to heat treat thickness using a ten degree angle, just to be safe. Once the edge is complete change to a 5 degree angle and continue the grind. Coating the bevels with lay out blue, will help to keep the process centered. Write down the angles used for future reference.
Grinding, using specific angles is less important than being able to grind a matching bevel on the opposite side of the blade and then being able to duplicate the grinds that you find most useful.
Happy grinding, Fred
 
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