Stropping success! ... and frustration.

[pialia]

I just thought I'd share my recent stropping success with you folks and ask a question about thicker blades.

First off, I just picked up my DLT strop kit with bark river compounds from the post office and went to work on my Spyderco Sage. Starting off it would barely cut paper cleanly, now it cuts phonebook paper with ease and I would have no trouble shaving my legs with it I got a bit more confident after finishing my Mora which was completely destroyed, I used the 400, 600 and 1000 grit sandpaper followed by some work on the Sharpmaker and strops. It is now as sharp or sharper than my Sage.

Now it was time for my friend's full sized Kabar which was basically in the same state as my Mora. I could easily get a working edge on this one, but no matter how much I tried to finish it off with the ultra fines on the sharpmaker or the green strop compound, it wouldn't really get scary sharp.

Any ideas why this might be? Am I just too much of a newbie who couldn't really get the angles right due to the thicker blade? The Mora was no problem so I'm sort of confused. I'm guessing I might have to reprofile it slightly to set the shoulders back a bit in order to get a sharper angle on the bevel. This, however, is kind of out of my comfort zone and I'm not planning on trying it out for the first time on a friend's knife.

Any and all help is appreciated!

 

[Robs92XJ]

When you say "not scary sharp", what do you mean exactly? Will it cut newsprint or shave arm hair? Will the edge "catch" on your fingernail or a plastic pen and not slip off?

The KaBar will have a more obtuse edge than the Spyderco or the Mora, but it should still be able to shave and slice paper well. So don't concentrate on reprofiling. Go back to a coarser sandpaper and make sure you are apexing the edge from both sides; formation of a burr on each side will be the evidence. Then, make sure you remove the burr with very light alternating passes before going to the higher grits. The edge should be very sharp even straight off of the coarse paper- it should have no trouble slicing newsprint. If you are not getting it right on the coarse grit you won't get it much better with higher grits.

If you aren't sure you're matching the angle properly, use the "sharpie" trick, it really works.

Once you're through with the 1000 grit, it should easily shave. If not, you either have a burr remaining on the edge or you did not apex the edge on the lower grits. Fix those issues with sandpaper, then once its good and sharp, lightly strop. I find it pretty easy to overstrop an edge when they are at obtuse angles, so use very light pressure and do not raise the spine up too much, you want the leather to barely brush the very edge. You don't need more than a few passes in each direction.

 

[HeavyHanded]

What test(s) are you using to determine the Kabar isn't as sharp as the others?
You're correct in thinking the geometry of the back bevel might be most of the issue (I'm reasonably certain it is). Can it shave some arm hair but not cut paper well? The Kabar might have an inclusinve angle in the high 30s to low 40s - I'm not familiar with the Sage, but if like other Spydercos it has approx 30 degree inclusive, the Mora is about mid 20s inclusive - these knives will cut better with a lot less fuss. IMHO more obtuse edges perform much better with a less refined edge unless we're talking about a hatchet or other dedicated chopper - in which case the more refined the better. You can get a fairly obtuse edge (anything over upper 30 degrees inclusive) to cut well at the edge, meaning it might shave hair fairly well, but they won't perform very well at tasks requiring a complete pass through of the material to be cut (like crosscutting newspaper or even cutting heavy fabric). Grinding down the backbevel on that Kabar is going to be real chore but well worth it. If the kabar has been around for a while and only had the primary edge sharpened then its cutting efficiency will really be suffering. Does it perform light chopping tasks with good efficiency?

Shaves hair but performs poorly on variety of cutting tests = poor geometry. Grind back bevel or prep with coarser edge and retry.

Doesn't shave hair and performs poorly on variety of cutting tests = failure to properly grind new apex or edge rounded under the strop.

 

[confucius37]

also consider that the Mora is a Scandi grind (i'm assuming its a scandi) and thus much easier to keep the angle when using a strop and sand paper setup. When you go to a grind that has a secondary bevel, its much harder to keep a consistent angle with strop and sand paper

 

[pialia]

Great tips, thanks a lot. I'll probably do some more work on it tonight and see if I can't do a better job. My friend pretty much gave the Kabar to me to help my learning process, figuring that the carbon steal wouldn't be too much of a hassle. I'm glad I'm not playing around with something more high end.

In its current state it will cut the type of paper you have in your printer, not shave hair nor cut phonebook-type paper.

I'll update with results when I've played around with it a bit more.

Thanks

Update:

Gave it another go, this time tying the sandpaper to the sharpie rods. Pretty much instant success. It now push cuts phonebook paper I'm a little disappointed in myself in that I wasn't able to freehand sharpen the Kabar, all though I have freehanded before and had very good results. I blame the Kabar grind!