1084 and some puukos

[RobN]

I previously posted about some difficulties with heat treating bits of old harrow tines. Since then, I've gotten a fair quantity of 1084 from Aldo, and some 5160 from Jantz that I haven't done anything with yet. The two puukos on the right are made of the 1084 and are the same pattern aside from one having the grinds polished and the other not. Not sure which look I like better. The wood is curly birch finished with pine tar. Super traditional, except that I cut holes for the tangs instead of burning them in. The third is another recent project in stainless and ebony. Not traditional at all.

Forging that 1084 is a completely different experience from the harrow tines. It's like forming a stick of butter in comparison. I have to wail on the harrow tine steel to get it to do anything. The 1084 actually moves when I hit it. I didn't know different types of hot steel could handle so differently. I'm wondering what the 5160 will be like.

I heat treated a few test pieces like I did before. The one I tempered at 400 (according to my oven thermometer) broke with a fair bit of effort, the one I did at 450 bent 90 degrees but seemed a bit soft when I filed it, so I'm tempering at 425 for, hopefully, the best of both worlds.

I think my next projects will be a leuku or two and then some kitchen-y type knives.

Comments welcome.

 

[Stacy E. Apelt - Bladesmith]

They look good. I would stick with the ground bevels. The polishing you did is washing out your grinds, as you see on the stainless one.

Not sure what your bend test was about, but for a puukko, 400°F for an hour, done twice, is a good hardness. 425°F is fine, too, but a tad softer.

At a 450°F temper, the steel shouldn't have bent easily to 90° or filed at all. I suspect something was wrong in the hardening steps.

 

[RobN]

Yeah, I was just looking at pics of some other puukos I've been using as inspiration. I'm noticing that Joonas Kallioniemi, for example, who does a lot of shiny puukkos, but they're not really polished. They're just ground with a very fine belt. They look polished in a lot of the pics, but you can see the grind lines in others. The ones that are polished do have sort of washed out grinds. Guess I need to invest in some finer belts.

What is this about? The spots you can see here?

I assume it's from uneven heating in my forge? They show up when I polish and don't polish out, no matter how fine I go. They don't bother me aesthetically on this particular knife, but I wonder if they represent a structural problem in the steel.

 

[RobN]

Also, I'm questioning the validity of my testing. The knife pictured here is one of the harrow tine knives and it carved that spoon from oak along with another from maple and a fair sized maple bowl, then dug that hole through the board, made all those stab marks, still has its tip intact and will still shave hair off my arm. I would not expect that based on what happened with the test pieces. Maybe it's just not a good test?

 

[FL_Jimbo_K]

Stacy said what I thought, the polishing detracts from your work, the center piece looks just says "puuko". Thanks for sharing your 1084 experience.

I have a question about your oven; have you checked how accurate your oven thermostat is? Most are not nearly as accurate as we'd like. And the plus/minus on your 450 setting could get you quite a bit higher.

Please keep pictures coming sir.

 

[GHEzell]

Keys to polishing blades and not washing out your grinds...
I use a bar of steel (1x12x1/4 inch, but measurements are not critical) to hold my sandpaper, but wood or micarta works just as well as long as it doesn't flex. I cut the sandpaper 2 1/4" wide, spray the center of the bar with spray adhesive, then wrap the piece of sandpaper around it so that 3 of the 4 sides of the bar are covered. If you wrap the bar with the entire sheet of sandpaper, it will have enough 'cushion' that it will round off things ever so slightly, which is fine for achieving a slightly convex surface, which is precisely what you do not want on a scandi... Maintaining a precise angle to the surface being sanded is critical, I clamp the blade so that the surface being sanded is level instead of trying to tilt the sanding block to the angle of the bevel, and practice keeping the block level as I sand. With practice you can get pretty good at keeping everything level and flat. Work the bevel until all the previous grit marks are gone, then move on to the next bevel. When all the bevels are sanded smooth, move on to the next grit of paper. Another option would be to use EDM stones instead of sandpaper and re-flatten as necessary.

It is hard to say from the photos exactly what the marks on the blade are, but they appear to be either a nie/nioi type phenomenon that indicates the blade was slightly over-heated when austenizing, or they could be alloy segregation....

Also, get a decent oven thermometer so you can be more sure of your tempering temperatures. Ovens are notoriously inaccurate.