Hollowing out / re-grinding the main bevel of a kamisori

[cotedupy]

i.e. the mild steel or iron side, not the ura.

Has anybody got any tips about how best to do this? Assuming I don't have one of those traditional Japanese scrape-y things (are they called 'sen'?). Slip stones? Sandpaper round a bit of dowel? Power tools?

Also - at point would people think it necessary? I have this very nice old razor, shaves wonderfully, but had quite a lot of wear when I got it. It's alright on stuff like cotis and softer finishers, but I would say annoyingly sticky on harder jnats and stuff. So should I be thinking of tyring to sort that?

(@Gamma Keith - I think I've read you've done this a few times, got any tips or thoughts...?)

 

[Herrenberg]

Not an expert, but a few points.

What's worked best for me, after trying diamond files, and learning how poor my control over a Dremel can get, is sandpaper wrapped around a dowel or pencil. Some here wrap around wider things like cork or rubber tubing, but I couldn't control that well enough to not scratch up the real bevel, mess up the wear strip, etc.

"Annoyingly sticky" is one trigger point for doing this, yes, but there's a worse one: finding out there's one part of the bevel you are just not reaching very well because of the large flat area you are engaging with when honing. At that point, the choice is accepting mediocrity, using tape, or breaking out the sandpaper and the No 2 pencil. Easy choice for me because I hate the first two options.

A confounding factor is that I really like how these kamisoris with the large flat area glide over the skin.

 

[Gamma]

Nelson’s method is w/d paper on a snapple bottle. It worked for my Kamis. Radius matters though, always check.
My method was a sanding drum on a Dremel. Don’t do that.

 

[Lord Fatboy]

Nelson’s method is w/d paper on a snapple bottle. It worked for my Kamis. Radius matters though, always check.
My method was a sanding drum on a Dremel. Don’t do that.

Agree. I did the same with the Dremel. There is trial and then there is error.

 

[cotedupy]

My method was a sanding drum on a Dremel. Don’t do that.

Agree. I did the same with the Dremel. There is trial and then there is error.

and learning how poor my control over a Dremel can get

Haha! Good. I was hoping people weren't going to say I should be using a dremel, cos I'm nowhere near good enough with one to want to go anywhere near this razor. I've got access to a lot of various belt grinders n stuff, which are easier, but certainly wouldn't fancy my chances with a dremel.

But sounds like a WnD progression wrapped around something suitable is the order of the day anyway. Cheers all!

 

[cotedupy]

A confounding factor is that I really like how these kamisoris with the large flat area glide over the skin.

Oh that's an interesting observation. This is the only kamisori I have, or have ever used, so don't have anything to compare against. But certainly the thing that amazes me about it is the feel, smoothness, and lack of irritation from something that shaves as incredibly closely as it does. I'd put that down just to being a good razor and good tamahagane, but perhaps there are other factors at play too!

 

[Eastcoast30]

Well, it looks fine to me. Many used kamisoris look like that. But if it hones and shaves well, I would leave it alone. There's a lot more wear required to turn it into a flat wedge.

 

[Gamma]

Typically, it would be expected to regrind something like that. If the blade is honed correctly, those large flat areas will become very polished. If you shave with a low angle, and get 'too low' rounding a corner or curve, those mirrored sections can literally stick to your face. With perfect technique, I suppose it might not be noticed. But, ideally, you don't want to see a ton of polished surface on the Omote. If that is a typical clad Hagane/Jigane blade, take care when grinding and honing, it's easy to get carried away. Which is why there are so many worn out cheapo Kamis on fleabay....

 

[Steve56]

I used sandpaper on a water bottle to regrind one.

 

[cotedupy]

If that is a typical clad Hagane/Jigane blade, take care when grinding and honing, it's easy to get carried away. Which is why there are so many worn out cheapo Kamis on fleabay....

Yeah, that was one of my worries about using power tools. I wouldn’t really have any experience with how deep the jigane goes on kamisori. Will watch out for it!

If the blade is honed correctly, those large flat areas will become very polished

This isn’t necessarily the case. A lot depends on the cladding, the progression, the finishing stone, and how they all play together. There for instance I’ve very specifically tried to emphasise kasumi contrast between the iron and tamahagane. It’s not an easy thing to do, but you can get that effect with some effort.

 

[H Brad Boonshaft]

Find a piece of PVC or ABS plastic pipe or fitting that matches the contour or a bit larger to make a wider, shallower belly, probably about 2 inch OD.

Wrap the plastic with Yoga mat or 6mm craft foam and 220 wet and dry. You can shim with drawer liner or 1mm craft foam to adjust the contour.

Set the razor on a 12x12 yoga mat or 6mm foam to secure and cut a new belly sanding parallel to the edge and spine.

 

[Steve56]

When you’re done re-grinding the hollow, you can lay a piece of sandpaper on the hollow, grit side away from the steel, and use it to shape a little piece of uchigumori, koma, or a fingerstone to polish the hollow sword-style.

 

[J B Addis]

For the two I've done I've used a ~2" diameter cylindrical 80 grit pink Pferd die grinder bit held horizontally in a drill running at a medium-low speed. It's pretty fast but controllably so. I cleaned up the scratches with sandpaper over a cork and kasumi'd with 400 then 800 grit silicon carbide powder. I intend to make a sen the next time I have to do one though, they're fairly simply constructed tools.

 

[thp001]

Find someone you trust who owns a high quality belt grinder with the right abrasives.

 

[cotedupy]

Find someone you trust who owns a high quality belt grinder with the right abrasives.

Haha... I have *ALL* the grinders.

 

[Steve56]

Start making razors Oli, I’ll take the first one!

 

[cotedupy]

Start making razors Oli, I’ll take the first one!

Maybe one day! (Though I do sharpening rather than the grinding/production really, and also - it strikes me that a razor would be well tricky to grind. Very little margin for error. You'd probably have to get out all of your weirdest-shaped stones to hone it... )

 

[Singing in the brain]

I was looking for a thread like this some months ago.

I got a razor from a friend that i supposed needed the same treatment of ura. I tried two things and they both kinda worked. I took sandpaper to the razor and used the ura as a sanding block on a smaller stone. I had an inch of NP400 that got radiused this way. I also tried cutting a canal in wood using a gouge ( think chisel, but with an aburd smile) and then using that as a template together with sandpaper to shape what i thaught i needed.
Even if theres only a small amount of radius left, this should be enough to get a inversion of the profile.
Also tried profiling a naniwa conitioning stone and a coarse green sic-stone, and to use the now being slipstone as a base for coarse w&d.

 

[Singing in the brain]

You guys think its neccesary to get the radius exaktly or as close to the old one, or is it more imortant that it is made "more" hollow and wider and the contactpoints along the ura is made smaller? In that case a suitable half-round file or any coarse woodcarving slipstone with a narrow radius would suit just fine.

 

[cotedupy]

You guys think its neccesary to get the radius exaktly or as close to the old one, or is it more imortant that it is made "more" hollow and wider and the contactpoints along the ura is made smaller? In that case a suitable half-round file or any coarse woodcarving slipstone with a narrow radius would suit just fine.

Obviously I can't yet answer your questions here with any kind of experience-based knowledge. But just something to note - I don't think it's the 'ura' you're grinding there, it's the 'omote'. The ura is the other side, and god help you if you need to re-grind that!

In my pics in the original post: the first one shows the omote, the second is the ura.