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My method for grinding very long blades


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I want to share the method I use to grind our long rapier blades (up to 47" plus Ricasso and tang). First the distal taper, then the bevel.

 

To save time and belts, I ordered the last batch of blades waterjet cut so the outline is there already.

 

I scribe the edge centerline with a center-scribe tool I made, then I twist one of the eccentrical legs (see picture, the lege on the left) and can easily scribe the impact edge on both sides symmetrical to the centerline.

 

Center_Scribe.jpg

 

Then the blade gets mounted on a support made of square profile tube with threads that take finely threaded bolts which enable me to adjust the distal taper along the blade. These bolts are spaced at 10cm = 3.9". To the sides of these bolts are smaller threads (M5 = 0.2") which take the clamping bars. With this support, I grind the distal taper on a table with a limit stop so there's no need to measure, just grind until the support hits the stop.

The clamping bars need to be moved once, to reach every spot along the blade.

 

Distal_Bolt.jpg

 

Grind_Support.jpg

 

After doing this on both sides (with doubling of the taper for the other side), I grind the bevels with the help of a jig made of two steel plates, two hinges (squeezed in the vise to eliminate play), a limit stop, an adjustable guide angle and an angle adjustment bolt. The angle can easily be checked with the super-handy digital angle meter. I simply put the jig on the belt grinder table and slide the support with the blade along the guide, then readjust the angle and grind again. This is repeated along the full length of the blade, usually I readjust the angle every 3" or so. A typical rapier blade ranges from 30° down to 10° bevel angle. From the top the remaining impact edge can be seen quite well.

 

Bevel_Jig.jpgBevel_Jig_Hinges.jpgBevel_Grinding.jpg

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any chance you could show it in action?

 

-Gabriel

The fundamental cause of trouble is that the stupid are cocksure, while the intelligent are full of doubt. -Bertrand Russell, philosopher
follow me on Instagram @raggedravenforge

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I SHOULD try something like this. But it seems like I always end up going back to free-handing it. I feel like I can usually get it right that way.. but I'm sure jigs like this speed it up quite a bit. I just can't get used to using them.

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Thanks a bunch! :D

That last picture, would I be right in thinking that the edge being worked -the upper- would also have to be aligned horizontally, in other words perpendicular to the direction of grinding to avoid the bevel just fading to nothing as the blade width narrows?
Wouldn't this alignment out of center give problems with the bolts that support the proper distal taper running into different parts of fullers and even bevels in the narrowest cases?
I have a feeling I would add to the bolts with a flat bar that can be adjusted in both ends and then supported along it's length.

(provided you want the same angle along the entire length, I see that you stop and adjust since you go from 30 to 10)

Edited by Steffen Dahlberg
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While grinding the angle I always watch the scribed lines of the edges from above (which is my alignment). It is tricky in my case, where the angle of the bevel changes continually along the blade. Yet, practically it works really well. If the angle is correct and I don't grind over the scribed edge, the bevel is correct. I use a finer belt here, like a 120grit or so to not mess it up.

 

As for the video request, my camera takes good still pictures but really crap videos. I also need a second person to hold the camera. I hope I can borrow a proper camera soon and film it.

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  • 6 months later...

Finally another update on grinding rapier blades. I have developed the angle grinding setup a step further. Now There is a spring loaded linear table that adjusts the distance to the belt and a goniometer to adjust the angle of the blade. The blade is mounted on a U-profile as before, which runs in ball bearings without play. The accuracy of the finished blade is within 1/20 of a millimeter

 

No need for files anymore :D I just need to finish the surfaces with sandpaper.

 

Goniometer.JPG

Goniometer_Angle.JPG

Goniometer_Action.JPG

Blade_Angle.JPG

Ground_Blade.JPG

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