Hapstone v8 sharpening help

[dflores]

So I previously had a v7 that I sold and thought I would try again with a v8. My problem has always been having a very wide bevel at the tip of the knife. I believe it’s me not positioning the knife correctly on the table. If anyone can help a bit with some tips on blade positioning that would be great. Tried searching but couldn’t pin down something specific for the issue.

 

[kreisler]

That's the advantage of freehanding. Let's say you buy a blade (with pronounced 3D-bellies in several directions, like the Fox Suru) and the factory used robots to create an even-width bevel along the entire edge lenth (unfortunately this was not the case with the Suru lol). Then it is very easy to maintain this even bevel geometry by freehanding: one adjusts the freehand sharpening angle mini section after mini section (see Michael Christy on the youtube), always matching the factory angle. This works, as long as the thickness behind the edge doesn't change.

 

[dflores]

I did section sharpening on a kitchen knife and it turned out better, but the problem I have is with knives with pronounced bellies like a traditional drop point. I saw some videos where they position the tips behind the edge of the table which changed the angle. I sharpened a prong knife under 4” the way they say in instructions with the edge off the front and straight from heel to top and it destroyed the edge with a very large bevel at the tip. I think I’m going to see if goodwill or any place has some cheap used folders for sale and try the tip behind the table works out better.

 

[c7m2p3]

Most of the time this is due to either clamping the blade wrong, or the actual knife grind not being perfectly consistent throughout the edge. As the blade gets towards the tip there is less room to thin down to an acute angle so there can be more material at the apex that must be ground away which results in a wider bevel.

Contrary to popular belief, the angle does not actually change the further you get from the pivot. There have been a few threads with people far better at geometry and math here that explain it with numbers and graphs far better than I could. I am sure I could dig up those threads if there is interest for them.

At the end of the day your options are as follows: You could change your angle and essentially try and sharpen the knife in two stages. Back toward the heel to the middle of the knife, then do the sharpie trick and reset your angle from the middle of the knife to the tip in order to keep a roughly consistent bevel width. You could just forget about it and just sharpen at one angle and have a wider bevel at the tip which will require some strenuous grinding on your part towards the tip of the blade. Or, you could try and find some method of "shimming" the knife so that it sits in the clamp or jaws of the guided system in such a way that towards the heel of the blade you are at one angle (20 degrees lets say) and toward the tip it is slightly more steep (say 22 degrees). Good luck