My experience using a sen knife, and why I love them so much

[White Nomad]

*note: I figured this would be the place to post this but if it needs to be moved, sorry*

So I've been forging for a little bit now, and due to financial constraints, I have been mainly doing all my grinding and whatnot by hand with files and sandpaper, and only with the last year or so bought myself a small bench sander. I've been using files for a long time, but with the files I have, I've found that the process of filing a blade down and smoothing it out can be quite a tedious task. Then I discovered the sen knife.

For those who don't know, a sen knife is an old Japanese (from what I know) tool, which I can best describe as a thick drawknife for metal instead of wood. They're used to shape katanas after they'd been forged but before the heat treating. Where files make a series of small 'cuts' in the metal and make a lot of small filings, a sen scrapes the surface almost and makes a chip similar to one you'd see on a metal lathe. 

While it may just be my inaccurate judgement, I feel like i can remove a lot more metal a lot faster using a sen than regular files. I find it great for shaping bevels and just all round blade work. I would even go as far as to say I remove more metal with my sen than using my bench sander, however it's a very small model and I only have fairly cheap and basic sanding belts, and I'm not that great at using it. I believe that if you have the time and resources, you should make a sen knife and give it a try. If you do use them, let me know what you think of them.

If you do decide to make one, here are a few tips from experience; Spend time making sure the bottom of the blade is flat and that the blade itself isn't curved or warped. If the blade isn't flat and straight, you'll end up carving deep channels into the metal rather than creating a smooth surface. Another tip is to not push down into the metal too hard. All you'll do is run the blade deep into the metal and/or have the blade jump across the surface. If you make one, use a HC steel, I made mine from a chrome-vanadium masonry chisel. And finally, do anneal and soften your work piece before using hand tools on it, it's a far easier and better experience. 

Anyway, these are just by experiences and observations, if I'm wrong about something, do correct me. And if you have any questions, tips or other comments, do leave them, I'll try to reply to anything that pertains to me. 
Thanks for reading
-Novak

[George N. M.]

Dear Novak,

Is there any chance you could post photos or a video of a sen knife in action or links to someone else using one?  Your description kind of sounds to me like using a wood chisel but on metal.  My first reaction is that it would be hard to do this because of the resistance of the harder material.  I suppose the resistance depends on how much material you are taking off in each single pass.

Also, I would think any comparison with hand filing would have to consider the condition and quality of the files.  My experience is that filing with an old, dull file is frustrating because you don't move much metal but a new, sharp file is a joy to work with.

Thanks.

"By hammer and hand all arts do stand."

[Irondragon Forge ClayWorks]

I made one years ago from an old file. It is like a wood draw knife only the blade and handles are straight and the cutting edge is considerably shorter. I don't have a picture and mine seems to have sprouted legs and walked away. If you google Japanese sen knife there is a lot of info and videos on them.

[White Nomad]

It's a bit of a long video and mainly focuses on the making of a sen, but this video has some stuff in it:

 

[pnut]

Hot rasping and a sen are probably the most efficient ways to remove material by hand that I know of. I've yet to make a sen myself but the LT. at my local fire department is also a black/bladesmith and I used the one he made. I was pretty impressed with how easily and controllably it took off material. 

Pnut

[White Nomad]

I've tried hot rasping a few times, but I'm very cautious of accidentally burning myself on the hot metal. Also I find that I have sometimes accidentally bend the work piece from putting too much pressure on the filing strokes. 

[JHCC]

I made a sen a few years back, and it was a miserable failure. However, I attribute that to my own lack of skill rather than to any intrinsic deficiencies in the tool itself. 

[White Nomad]

That's fair. The first ever attempt I had at making one was horrible. It's really up to personal preference, and different tools have different uses