Manual Knife Flattening & Thinning?

[eveled]

Eli Chaps If thinning is the goal especially on a wide knife. A plain old hand held 4inch carpenters belt sander will do a good job. Mount it in a bench vise. I did a cleaver like that it came out great. Go slow take a lot of breaks it will get hot.

I can’t justify a knife makers bench belt sander, but the carpenters one is more useful for other stuff.

If I realized how deep some of the scratches on my Buck 104 were I definitely would have started with the belt sander. I won’t make that mistake again.

 

[Eli Chaps]

Eli Chaps If thinning is the goal especially on a wide knife. A plain old hand held 4inch carpenters belt sander will do a good job. Mount it in a bench vise. I did a cleaver like that it came out great. Go slow take a lot of breaks it will get hot.

I can’t justify a knife makers bench belt sander, but the carpenters one is more useful for other stuff.

If I realized how deep some of the scratches on my Buck 104 were I definitely would have started with the belt sander. I won’t make that mistake again.

Yeah I think that's what I would do next time and recommend to others. I'll smooth out the scratches in this one until I'm satisfied and be happy with the experience gained.

 

[bgentry]

It looks like you are making good progress. It also looks a bit inconsistent from top to bottom, like the middle is getting most of the attention. I'm not sure how you have the sand paper set up for sanding. On a sanding block, by hand, glued to a flat surface, etc.

It's my firm belief, that to make it look good cosmetically, you need some give to the substrate. Something like a sanding block that is made of foam or rubber. Or a sanding belt in a belt sander.

Years ago, after buying Murray Carter's sharpening videos, I took my favorite kitchen knife, a Richmond Artifex 240mm Gyuto, and laid it flat on a 1000 grit waterstone. I then tried to do Murray's "thin the knife before every sharpening" method. I'm sure it removed metal. Because it scratched the daylights out of my blade. It was left looking pretty sorry. Murray says that gives the knife character. I say it just makes it plain ugly if you stop at the 1000 grit. Even if you go to 6000 grit (as he suggests) it's STILL ugly because the blade is not flat and a stone will not conform to the valleys and dips in a knife blade. It will only scratch the peaks.

A few months ago I bought my Kalamazoo 1x42 belt sander and have been having a blast with it. At some point I pulled out my favorite Richmond and tried to make it look better with ScotchBrite belts. I quickly realized that I needed actual metal removal to get the big scratches out.

I believe I used 180 grit followed by 280 grit and then some medium ScotchBrite. I was pretty happy with the results. It's by no means perfect, but it's actually a bit thinner now, and has a pleasing matte type finish.

Here's the blade part way through the process:

https://drive.google.com/file/d/1XdKsobpuD9D-FM46W3AQ4d7z1MEpRGiu/view?usp=sharing

...and the final finish on the blade:

https://drive.google.com/file/d/1yCpaxz7fNyg0oxi9o0QJOgYlH8pWtjzw/view?usp=sharing

A belt sander makes this MUCH faster. It also has the side benefits of:

Making a very consistent scratch pattern from top to bottom because the belt is flexible.
Seemingly imparting a finer finish than the belt would imply because it's moving so fast.
Did I mention it's faster and easier?

Brian.

 

[Eli Chaps]

Thanks Brian.

I was wrapping the paper around a sharpening stone.

In good light it is actually pretty even although there is a spot on side near the tip that I could work some more.

And yes, for a knife this size, power is the way to go.

HeavyHanded warned me but I dove in anyway.

 

[HeavyHanded]

Thanks Brian.

I was wrapping the paper around a sharpening stone.

In good light it is actually pretty even although there is a spot on side near the tip that I could work some more.

And yes, for a knife this size, power is the way to go.

HeavyHanded warned me but I dove in anyway.

I picked up some metal grinding belts for my 3x21 handheld and blocked it in on my benchtop. This works great for initial phases of thinning everything - have done hatchets, several knives.

 

[tinfoil hat timmy]

Nice job.

I usually use a DMT plate with soapy water for something like flattening. Believe it or not, I did this with a stripped (not factory finished secondary bevels!) BUSSE COMBAT NMFSH, it was a CHORE. Its kind of intimidating seeing how much work lies ahead on something like that, I wish I had pics of it. It was a fun time.

I've done this to a good many knives and so far never found any production models that were perfectly flat... flat stones/plates don't lie.

I start out with sandpaper on a known flat surface, or diamond plate just to see what I'm dealing with. If it's close to being flat (rare), and not a great deal of metal needs to be removed, I'll use ~180 grit till I'm close to the thinness I want, then refine from there.
If it's not close to flat (most), or a lot of metal needs to be removed, even if it is flat, I'll take it to a 100 grit sic stone to get it close, then ~180 on known flat or diamond plate, and so on.

Speaking of flat surfaces for sandpaper, I recently acquired this, and really like it.

Depending on blade steel and how much needs to be removed, it can take a lot of sandpaper. This is why I value a coarse sic stone so much.

The coarse sand paper I wear out can be used in the finishing stages.

Abrasives I've used are most all grades, grits, and type of sandpaper, silicon carbide stones, aluminum oxide stones, & diamond plates. All paper used dry.
Nothing powered for me, I'm in no hurry, and take my time.

I'm always surprised how many premium blades are so far from flat.

What is the tool that you acquired? Could you explain about it and tell us what it is? I have a guess, but guessing is less fun.

 

[jpm2]

Nice job.

I usually use a DMT plate with soapy water for something like flattening. Believe it or not, I did this with a stripped (not factory finished secondary bevels!) BUSSE COMBAT NMFSH, it was a CHORE. Its kind of intimidating seeing how much work lies ahead on something like that, I wish I had pics of it. It was a fun time.

What is the tool that you acquired? Could you explain about it and tell us what it is? I have a guess, but guessing is less fun.

In the past, I used sandpaper on a diamond plate when I needed something flat to grind on.
Been meaning to build something like this for years, never got around to it.
It's a little pricey, but I have an endless supply of various sandpaper (mostly used), and use it several times a week. It saves a lot of wear and tear on my stones & plates when re-shaping knives and other stuff.
I should do an update in this thread about it. There's other ideas for sandpaper holders in that same thread.

 

[eveled]

Eli Chaps here is my set up. Although the manual doesnt say to put it in a vise, it does say it can be used on metal for a satin finish. There is even a replacement softer graphite pad to replace the steel shoe for that purpose. (I don’t have that) If anyone tries this it is at your own risk, do not lock the trigger down, if the sander vibrates loose out if the jaws it could be a disaster.

The clever had a bad factory plunge line. It seemed it didn’t go deep enough into the machine There was an arc of full thickness blade from spine to edge, the first 1/4” of the edge was as thick as the spine. This is how I fixed it. 120 grit aluminum oxide belt.