![](https://s3images.coroflot.com/user_files/individual_files/539275_j4_arlllvhgxgj2wbc7oeumf_.jpg)
Blade grinds seem easy until you think about them. Once you realize that there are convex, concave and flat planes all intersecting each other in multiple places and along a curving profile that must remain a constant width; not to mention the fact that for aesthetics, you are trying to control how and where all those lines intersect...well, most peoples minds blank-out.
Before you look at the rest of the pictures, take a moment and see what you come up with first. If you have time, try to model it then look at the rest of this project.
![](https://s3images.coroflot.com/user_files/individual_files/539275_c0kvxlsuymayjigyfdyjez0vq.jpg)
The biggest challenge is keeping the edge a constant thickness. If that edge isn't a constant thickness then the honed edge (or secondary edge) will vary in height along the blade and just look awful.
On more complicated grind like a tanto the intersection of the tip, top and belly need to be tightly controlled for the engineered performance of the blade (the belly is hollow* (*concave) ground with a very thin honed edge for perfection in slicing while the tip is a thick flat or apple-seed* (*convex like) grind for puncture). Tight control is also needed for the aesthetics, all three grind need to converge at the sharp transition points otherwise the blade just looks wrong.
![](https://s3images.coroflot.com/user_files/individual_files/539275_gzvy0qdrz7s8qjy_zsrem3ujh.jpg)
I'll use this knife as an example. it is composed of two hollow grinds, (a top and belly that converge at the tip). Followed by a triangular secondary grind for the honed edge.
![](https://s3images.coroflot.com/user_files/individual_files/539275_6m0ifpyjuunt5lijg6txboyr3.png)
The most elegant solution I have found so far is to use a simple sweep-cut. I create a simple profile that contains all the critical information. I then make a path that follows the blade profile. This produces a double faceted feature that can change in up to 5 degrees of freedom and yet is controlled by 2-3 dimensions.
![](https://s3images.coroflot.com/user_files/individual_files/539275_ezdk2xw4aprwg_bpgo08kmrem.png)
The secondary grind is a much simpler form of the primary.
![](https://s3images.coroflot.com/user_files/individual_files/539275_bfnegj9qziwop9z3mnblgcprk.png)
The top grind is another variation on the same theme. It does however require a bit of playing with to get it to converge perfectly but it is limited to a single dimension.
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