How To How to sharpen a half moon shaped blade

K

knifeaficionado

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Jul 30, 2016
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Hello,

I have this project. In the picture below you can see the shape, it's around one inch radius. The desired outcome would be similar to what you can see in the first image(the sides don't have to be straight, though).
The blade will start as 0.06 inch thick flat piece of metal that looks like the second picture.

I would like to get some ideas to get this done right.


Thanks!

blade2.png


blad.png
 
What Don said. Or, if you have a 2x72 and a small wheel holder, I'd make the blade to match the closest small wheel diameter and use that.

The "right" way to do it would be to dress a radius on a surface grinding wheel and use a sine plate to set your angle. If you have a surface grinder, but no radius dresser, you can dress it with a norbide stick. If you don't have a sine plate, you can tilt your magnet.
 
Thanks, much appreciated.
What kind of drum sander I shoud use? There's so many machine types and sanding bits... It would need to grind already hardened steel.
Any idea on the price range of the proper tool?
 
If this a one time affair, you can probably get by using fine sandpaper wrapped arround a dowel or a deep socket of the approiate diameter, and hand sanding. If you want power you can buy drumb sanders from most woodworking supply places: Wood craft, Rockler, Homedepot, Lowes etc.
Jim
 
Yeah, you could probably rough it in with a half round file, get it closer with a drum in a drill press and finish by hand sanding.
 
I would need something fool proof and for several blades.

What kind of drum sanding piece would work for hardened steel? I assume drum sander in a drill press is a good way to go as long as it's the right size.
 
Depending on the size, gesswein sells some drum sleeves with 3m cubitron ceramic grit. Those would probably be my choice if available in the size you need.
The cheap AO ones I've used tend to strip the grit off pretty fast on steel. Like I'd expect using a couple per blade.
 
Geoff Flato said:
Depending on the size, gesswein sells some drum sleeves with 3m cubitron ceramic grit. Those would probably be my choice if available in the size you need.
The cheap AO ones I've used tend to strip the grit off pretty fast on steel. Like I'd expect using a couple per blade.
Click to expand...

Those would probably work well, do you have a link for those as I didn't find them on gesswein.com
 
Unfortunately not, it's something I saw on there a few weeks ago, but didn't bookmark or order, so I don't have a part number. Their site sucks to navigate so it'd be as hard for me as you.
A search for "sanding sleeves" might give something
 
Any suggestions on how to finish the blade for ideal smoothness and sharpness after going through it with a 120 grit drum sander?
 
Geoff Flato said:
A piece of the right size wooden dowel wrapped with sandpaper
Click to expand...

That sounds smart. Do you have any suggestions on how to attach the sandpaper? I was thinking maybe cutting a vertical line towards the center of the dowel's radius and folding in the paper, might need some glue though.

What would knifemaker commonly do to finish the blade's edge?
 
I'd just wrap the paper around a regular dowel. Keep moving it to a fresh part of the sandpaper as needed.

As for the edge everyone does it differently.
Something like that I'd just hand sand the inside bevel as discussed, and then lap the back flat with a piece of 600-1500 grit sandpaper on a piece of glass or granite.
Find sandpaper on a hard backer is common practice for sharpening the blades in woodworking hand planes, I see no reason it wouldn't work for this
 
I use a larger round wooden dowel I cut a slot vertically in and then put a piece of sandpaper in it and twist it around until tight and then start sanding the bevel and tear of a strip as it wears to reveal fresh paper as I need--easy to change paper an keep it fresh doesn't seem to critical on the diameter i usually use like a two inch stick.
 
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