Grohmann #R350S

[afishhunter]

Grohmann #R350S two blade jack knife.

My question:

Is it worth the time and effort to reprofile the blades to a knife-like edge geometry?
(all I have are a couple diamond plates. 400 and 600 grit, I believe.)

The paperwork that came with my #R350S, says to "sharpen" (note quotes) the blades to (an ridiculously obtuse) 50 to 60 degrees inclusive angle.
This was verified in an email I sent to Grohmann, shortly after receiving this knife.

When I was taught how to sharpen a knife, axe, hatchet, scythe, etc. 59 or 60 years ago, I was taught a knife should be sharpened to 20 degrees inclusive, by my da, uncles, great uncles, grandfathers, granny, great granny, great grandfather, and great-great granny.
Somewhere around here, I have a late 1950's early/mid 1960's sharpening guide from W.R. Case & Sons*, that also says 10DPS/20 degrees inclusive for a knife, be it a pocket knife, sheath/hunting knife, or a kitchen knife. 10DPS, give er take a degree or two for "human error".

I was also taught an axe, hatchet, tomahawk, adze, and other chopping tools should be sharpened to between 30 and 40 degrees inclusive, and the closer to 30 degrees the better.

Anyway, I've not carried this #R350S yet. I need whatever knife I pull out of my pocket to cut and slice.
Using the fingernail sharpness test, both blades slip at around 25-30 degrees anywhere along the cutting edge.
"Not. Sharp." Sharp don't slip until at least 60 degrees.
Like I said, a significant reprofiling is required.

Aside from the "my axe is sharper" factory edge geometry, it seems like a nice knife.
Well built, at any rate: Nicely centered blades, no noticeable gaps anywhere, no wiggly-wobbly blades, the blade pulls are both a "5" in my estimation. The same as a 91/93mm SAK.
Backsprings are both flush open and closed. (no half stops)
At 3 13/16 inch / 97mm closed, (according to my ruler) it isn't "too small" nor "too big".

View attachment 1431086

*at one time Case included a sharpening guide with every knife they sold.

 

[FortyTwoBlades]

I say give it a go. Worst case scenario it's too soft for so low an angle and you'll just have to stabilize the edge by microbeveling it, but as it is now you're not going to actually use if for much so you may as well turn it into an actual usable knife.

 

[Glock Guy]

Glad to see you picked up those diamond plates!

What it really boils down to is: Does the knife cut the way YOU want it to for what YOU are using it for?

If the answer is yes, then leave it as is. If not, then you need to sharpen/reprofile it. The key is to start with a higher angle (15-20 dps) because you can only take steel off - you can't put it back on. You can always raise the angle if you want, but I would recommend trying it out at the lower angle first. You might be surprised how much just putting a fresh edge on your blade changes it!

I wouldn't get too hung up on the actual angle. A lot of knives are shipped with what I would consider overly obtuse angles. I've seen ZT's and Hinderer's that are sharpened to what seems like 60 degrees inclusive. Here's the thing though - they were still sharp and were able to cut with the coarse finish on them.

Here are some quick thoughts on the angles you mentioned:

20 Inclusive (10 dps): Unless this is going to be a glorified letter opener, I would definitely NOT go this route as it would be just asking for trouble. I would not even do a high end kitchen knife that steep, much less an EDC knife that is going to cut more than paper or tape. You WILL (not might) roll an edge cutting anything even remotely hard.

30 Inclusive (15 dps): This is starting to get more robust, and will keep you from having to sharpen away your blade by fixing all the chips/rolls/etc. over time.

40 Inclusive (20 dps): This is my preferred angle for ANY type of EDC knife. It is robust enough to handle most cutting tasks like cardboard and the occasional zip-tie, and you won't have to worry about rolling an edge with that. If you do your job on the sharpening, it will be PLENTY sharp for anything you throw at it, and you'll be able to strop it back to hair popping sharp with just a few passes on a good strop. I've heard of a lot of old timers stropping those types of blades on the leg of their blue jeans, or even using the palm of their hands. I prefer a good strop though.

The other factor that plays into the cutting performance is how the edge is finished. A smooth and refined edge is great for cutting paper, but will not last long in real, everyday use. A toothier edge will serve you far better for pretty much anything other than just making a bunch of curly Q's with paper.

I would suggest reprofiling ONE of your blades to 20 dps using the 300 grit + strop, then testing it out. If you want it sharper, hit it with the 600 (+ strop again) grit, but KEEP THE SAME ANGLE.

If after that you STILL don't feel like it's cutting the way you want, then try lowering the angle another 5 degrees (15 dps) and rinse and repeat.

Good luck, and let us know how it goes!

 

[afishhunter]

Glock Guy
When I sharpen a knife, I always lay the blade flat on the stone, raise the spine just enough so the blade flats don't scrape/rub then go edge first the length of the stone. At the end of the stroke, I lay the blade flat again before lifting it, to prevent rounding the edge.
That is the method I was taught call it "60 years ago" (it might only be 59 years and a few months).

I've never been plagued with rolled edges, even when I worked in a auto repair or body shop, stripping electrical wire and cable, peeling critters and reducing them to freezer size pieces, or whittling/carving up to and including seasoned oak.

On the rare occasions I did roll an edge, a dry leather strop fixed it after a couple swipes.

 

[Obsessed with Edges]

For traditional knives in simple steels like these, the sweet spot for me is somewhere in the 25°-30° inclusive ballpark. Going much below 25° inclusive, these softish steels tend to get a little too delicate for me to have confidence in for the full range of normal EDC tasks. Things like very light contact against something hard will dent/roll the thin edge very easily.

BUT, if you dedicate such an edge to very specific fine-slicing tasks done at a light touch, these low-angle edges can be very fun to use. The secondary upside is, if it does roll a bit, a very thin edge like this is also easy to touch up or realign when it's needed.

 

[sodak]

Reprofiling those blades should be fast because they are thin. While diamonds work well for that, if you want to reprofile faster, a silicone carbide stone from Home Depot will be even faster (around $10), because as long as you use lubricant, you can bear down on the stone as hard as you want to. You'll only expose fresh abrasives as they wear away. Diamonds, once stripped out of it's matrix from too much pressure, leaves you with nothing.

I like diamonds for sharpening just fine, but for reprofiling, silicone or a water stone and that's a 10 min job per blade.

 

[bucketstove]

What it really boils down to is: Does the knife cut the way YOU want it to for what YOU are using it for?
...
20 Inclusive (10 dps): Unless this is going to be a glorified letter opener, I would definitely NOT go this route as it would be just asking for trouble. I would not even do a high end kitchen knife that steep, much less an EDC knife that is going to cut more than paper or tape. You WILL (not might) roll an edge cutting anything even remotely hard.
...

Hi
angle + thickness is key
10dps at 1mm is pretty robust
whats-the-lowest-functionable-angle-by-steel-type.1587190/#post-18129004 ..... Extreme Regrind , ~6DPS with 10dps microbevel, no damage in 50 slices into pine, hardwood flooring and plywood the edge eventually gets damaged while cutting metal (steel food can)