Manually Thinning K390?

[Eli Chaps]

I'm a freehand sharpener and while my edges are not BBB, Michael Christy, etc. level, I get my knives plenty sharp for their purposes.

After diving into Japanese cutlery, I've entered a phase of liking to play around with my knives to find what works best for the knife, me and it's purpose. This includes thinning. That might be just a certain distance up from the edge bevel or the whole primary grind.

What I haven't done, is messed with a high-vanadium alloy steel in this way. I have my S90V Manix that I could play with but the thought of a K390 Endela workhorse/experiment knife is really intriguing to me.

I do a lot of my current thinning, including on my J-knives, on sandpaper. Well, at least to set things. I don't polish and surface scratches or mars don't bother me a bit. It's why I don't have pretty things.

I have a spread of plated diamond stones, but man they can leave deep scratches, well beyond surface. Right now, I'm not investing in vitrified stones or power sanders.

What do you use? Should I leave it alone and just keep playing around with my more amicable steels?

[Wandering_About]

140 grit Atoma plate for the heavy work on reprofiling things like K390, S110V, Maxamet, and honestly anything else also, for me. It is a weapon! Does leave deep scratch marks though. My strategy tends to be to "kiss" the edge with the scratches of the 140 plate, then move to a 400 and raise then remove a burr with that to actually apex the edge. Usually I'm finishing with a 1000 grit stone, but suit yourself on the grit progression.

K390 has done quite well in my experience with a pretty thin edge. Thin edges, to me, are where you really get to know the differences between steels.

[Eli Chaps]

140 grit Atoma plate for the heavy work on reprofiling things like K390, S110V, Maxamet, and honestly anything else also, for me. It is a weapon! Does leave deep scratch marks though. My strategy tends to be to "kiss" the edge with the scratches of the 140 plate, then move to a 400 and raise then remove a burr with that to actually apex the edge. Usually I'm finishing with a 1000 grit stone, but suit yourself on the grit progression.

K390 has done quite well in my experience with a pretty thin edge. Thin edges, to me, are where you really get to know the differences between steels.

Thank you. Are you mostly thinning the edge then and not the full flat?

[Wandering_About]

140 grit Atoma plate for the heavy work on reprofiling things like K390, S110V, Maxamet, and honestly anything else also, for me. It is a weapon! Does leave deep scratch marks though. My strategy tends to be to "kiss" the edge with the scratches of the 140 plate, then move to a 400 and raise then remove a burr with that to actually apex the edge. Usually I'm finishing with a 1000 grit stone, but suit yourself on the grit progression.

K390 has done quite well in my experience with a pretty thin edge. Thin edges, to me, are where you really get to know the differences between steels.

Thank you. Are you mostly thinning the edge then and not the full flat?

Yes, I only thin edges. Have never done thinning on a primary bevel (which is often called a "regrind").

[Eli Chaps]

140 grit Atoma plate for the heavy work on reprofiling things like K390, S110V, Maxamet, and honestly anything else also, for me. It is a weapon! Does leave deep scratch marks though. My strategy tends to be to "kiss" the edge with the scratches of the 140 plate, then move to a 400 and raise then remove a burr with that to actually apex the edge. Usually I'm finishing with a 1000 grit stone, but suit yourself on the grit progression.

K390 has done quite well in my experience with a pretty thin edge. Thin edges, to me, are where you really get to know the differences between steels.

Thank you. Are you mostly thinning the edge then and not the full flat?

Yes, I only thin edges. Have never done thinning on a primary bevel (which is often called a "regrind").

Cool. I just connected the dots with your pictures I saw before. Thanks for input!

[Brock O Lee]

I've thinned out the primary grinds (FFG's) by hand for a bunch of steels, from Superblue and 52100, to S30V, M4, S90V and S110V etc.

I suspect K390 will feel very similar to M4, which is completely doable.

There may be better ways, but I used DMT plates in XC and C for bulk removal, and finished most of them on 140 grit SiC for a finish very similar to the factory finished satin FFGs.

Here are a few:
viewtopic.php?p=1043842#p1043842

[Eli Chaps]

I've thinned out the primary grinds (FFG's) by hand for a bunch of steels, from Superblue and 52100, to S30V, M4, S90V and S110V etc.

I suspect K390 will feel very similar to M4, which is completely doable.

There may be better ways, but I used DMT plates in XC and C for bulk removal, and finished most of them on 140 grit SiC for a finish very similar to the factory finished satin FFGs.

Here are a few:
viewtopic.php?p=1043842#p1043842

Thank you.

[vivi]

https://www.harborfreight.com/3-piece-2 ... 36799.html

I use the 180 grit plate to shape the bevel, then depending on the knife finish with that stone or polish up to 260 grit.

They shape K390 just fine, and leave a toothy edge that'll slice for months without any touch-up.

[Bill1170]

Thinning the primary bevel by hand with diamond plates does work, but it’s a lot of elbow grease required. Just like any other sanding/grinding task, you need to work successively finer grits, fully erasing the scratches from the coarser grit that came before, prior to moving up to a finer grit.

[ZrowsN1s]

I use a WE 130. With K390 if scratch marks dont bother you, start with as low a grit possible. Reprofiling the edge is gonna take a while. I use 50 grit diamond until I get near the edge, then 80, 150, 200, 400, 600, 800, 1000, 1500, 2200, 3000 and strop with 1 and .5 micron paste on leather. I spend the most time with the 400-800 stones. First getting out the deep scratches from the 50 grit, then refining. The 800 grit edge would probably be what most people prefer for a working edge, but I like to slightly polish that edge with the higher grits. I spend a 1/10th of the time with the higher grits than I do with 400-800 grits. On repeat sharpenings I only use the higher grits starting with 800. For me with K390 12-13dps is a good angle.

[Wartstein]

...
I do a lot of my current thinning, including on my J-knives, on sandpaper. Well, at least to set things. I don't polish and surface scratches or mars don't bother me a bit. It's why I don't have pretty things.
....

May I ask what kind of / grit of sandpaper you use for that?

I also don´t care for my knives being "pretty" (or actually like the look of used / scratched / patina-ed blades), and thin out on sandpaper too occasionally. Currently, though this is not exactly "thinning behind the edge or the whole blade", I thin / smooth out the shoulders of the H1 Pac Salt grind where the hollow grind meets the upper, rectangular part of the blade) to make it cut smoother through matter with larger diameter.

(Sorry, a bit off topic as I just realized)

[Eli Chaps]

...
I do a lot of my current thinning, including on my J-knives, on sandpaper. Well, at least to set things. I don't polish and surface scratches or mars don't bother me a bit. It's why I don't have pretty things.
....

May I ask what kind of / grit of sandpaper you use for that?

I also don´t care for my knives being "pretty" (or actually like the look of used / scratched / patina-ed blades), and thin out on sandpaper too occasionally. Currently, though this is not exactly "thinning behind the edge or the whole blade", I thin / smooth out the shoulders of the H1 Pac Salt grind where the hollow grind meets the upper, rectangular part of the blade) to make it cut smoother through matter with larger diameter.

(Sorry, a bit off topic as I just realized)

Usually just wet/dry SiC for the low grits and AlOx if it goes up some. There's some nice 3M paper out there with soft backing but I never seem to have any on hand.

[Matus]

Thinning the whole flat grind will be a majo PITA as you will have a very large area where blade is contacting the stone (diamond plate, really). Do as on better made kitchen knives (none if them have a full flat grind as that is about the worst one can make on a kitchen knife) - and add a very gentle convex over say 5 mm from the cutting edge and blend it into the edge ‘grind’.

[Wartstein]

Usually just wet/dry SiC for the low grits and AlOx if it goes up some. There's some nice 3M paper out there with soft backing but I never seem to have any on hand.

Thanks, appreciate it!

[Baron Mind]

Yea, diamond plates will work. Thinning the entire blade will take a long long time. Apply pressure towards the edge bevel for more immediate results.