Convex grind...first

rad148

rad148

Joined
Mar 5, 2001
Messages
1,086
Nope, not a "how do you do it?" post.
Just did a convex on a 52100 blade. Have learned how to in all other grinds and have some very sharp blades.
But this convex shape is something else. Stayed away from it for several years thinking I would not be able to, but used two mouse pads and dry sandpaper and am totally impressed :) ie Big smile.
Had to drop to 400 grit to get an initial burr on the edge length, then up to 1000, 200 at a time. (note: original blade came not so sharp).
Didn't take that long (about 1 hour) and is only my first try. Right now will part cigarete paper (edge or width) as though not there. Chopped some wood and other odds and ends and then stropped it on a leather jacket sleeve and that is all it took. Am beginning to delude myself that I may actually have a knack for free hand sharpeninng. Still, have read many say that convex is the easiest to sharpen and keep sharp, even out in the field.
Think I can do better the next time (more practice) and wonder what going up to 2000 grit will bring.
Question though (dumb one). When doing the the tip (upswept after the belly)? Should I be turning the blade to be perpindicular to the grind as normal sharpening or keep the blade straight. Is only the last 1/2" of the tip that is not super sharp right now.
Rad
 
I primary sharpen my convex blades the same way as flat or hollowgrinds - why have different methods. I have had some flat ground blades that I had trouble with the last 1/2" or so - probably because of the original grind - and found the best way was to change the angle for the last bit - I find this works well on butchers knives that become too thick as they are ground down.
 
rad148 :

When doing the the tip (upswept after the belly)? Should I be turning the blade to be perpindicular to the grind as normal sharpening or keep the blade straight.
Click to expand...

If you don't turn it, a very acute angle will be applied, which will take some time to form. But this does leave the tip very nice for ease of penetration and precision work. If you rotate the tip, the same angle forms as along the main blade body.

-Cliff
 
I like to rotate the blade so that the edge is perpendicular to my stropping motion. I've accidentally rounded blade tips when I didn't rotate the blade.
 
Tks Cliff,
As always your opinion is much respected. As you mentioned it leave s the tip very, very, pointy sharp which is what I did at first, and yes, the point rivals my most pointed spear point, Wayne Clarke grind that penetrates to a depth upparalled. So I have have seen this and wonder which is best...guess as always is what you want out of the finished blade.
JDEEBLADE also noticed your comment and guess it all comes down to experience once again. Please send me several of your blades so that I can practice ok? :D (sigh..in my dreams eh?).
Still, as mentioned this is my first try on convex, and the result is amazing, perhaps cause of the steel use? (by an MS?).
If this is what I can expect from Convex grinds, believe that I will transform all flat grinds to convex also.
I have other grinds that do not penetrate nearly as well when chopping or just cutting. Push cuts are are way above standard.
Makes me wonder why all blades are not convex. But suppose there is a very good reason for this.
Again..tks much Cliff. Not often do I get a response from somone of your caliber and appreciate your input greatly.

Buzzbait. Know excatly what you mean, and found this on other types of grinds, much to my chagrin. Is still a challenge I am trying to work around.
Hollow grind is cool, flat grind is cool, but wow, this convex put a whole new meaning to sharp and utility. Totally destroyed the edge yesterdy (well my relatives did) but took them a couple of hours to do so. Again, stroping brought it back to razor sharp. I am totally impressed. Each grind is meant for a certain task though. However...this hollow grid seems to suit all my needs, so far any way. Have not had a chance to try skinning with it yet, though think the blade shape would be perfect for this task.
Now am beginning to understand comments by others who like convex grind, almost as it is a well kept secret. Imagine that blade makers either love or hate this grind.
Rad
Tks for all comments and suggestions. Gotta love this forum.
 
I don't really think that convex grinds are a secret. It’s just that manufacturers have moved away from convex grinds, for production cost and aesthetic reasons, so users no longer even see knives with convex grinds. Outside of the high-end knife market, convex grinds are nearly impossible to find. You can’t exactly walk down to your local sporting goods store or WalMart, and find a convex ground blade. The best that most people can do to their existing knives, which sounds like you have done, is to leave the primary grind mostly intact, and merely convex the edge bevel. This will work for both hollow and flat grinds.

With that said, you are probably experiencing a few unintentional changes as a result of the convexing. Convexing an existing edge often results in a higher and thinner overall edge bevel, which dramatically increases cutting efficiency. It also leads to a higher level of polish than you normally get with a knife sharpener. These two changes are not directly attributable to the convex shape, but a helpful byproduct of the work. The same edge thinning and polishing can be done with normal “V shaped” edge bevels, but not as easily without machinery.

The actual change of the edge to a convex shape should result in two major differences. First, the rounded edge bevels tends to be a little more robust than a similar “V shape”; and as you noticed, the convex shape is MUCH easier to maintain with a little training. Stropping will often be all that is required to maintain the edge. I personally find the ease of maintenance to be the largest benefit.

A full convex grind is a totally different animal, with many more benefits and drawbacks as compared to hollow and flat grinds. This is where you get into wedging and substrate parting effects, which seem to be much more complicated.

It is amazing how people marvel at the increased cutting efficiency of a convex edge bevel. The thinning of the blade alone is enough to blow peoples’ minds. We’ve gotten so used to thick edged tactical prybars that we’ve forgotten just how much better a knife cuts when the blade is even slightly thinner behind the edge. This thinning completely transformed my Spyderco Military from a mediocre performer to an outright cutting machine. The convex shape of the edge allowed me to thin the blade with no loss of edge durability.

If anybody really wants to experience a full convex grind, a highly suggest that they look into a Blackjack knife from knifeware.com. Ken Warner makes some sensational convex ground knives, that won’t break your budget. They’re even small enough for everyday carry. I love my Blackjack Small, and am looking hard at the new Blackjack Slick. These models are often overlooked by knife users, but happen to be far superior in performance to most tactical production knives. If you’re not convinced by me, call Knifeware and talk to Ken Warner on the phone. He’s an even bigger convex grind fanatic that I am!!!! Ken really knows his knives.
 
Originally posted by rad148
Think I can do better the next time (more practice) and wonder what going up to 2000 grit will bring.
Click to expand...
I'm no sharpening expert, but from personal experience, the 2000 grit will put a really smooth finish on the edge. While this is good for push cutting, it won't have as much "grip" or "bite."
 
The main problem with convex grinds is you sit around watching TV stopping away at mousepads on perfectly sharp knives night after night, and your wife and friends begin to glance ever further askance at you. It does, however, keep the in-laws at bay.
 
I just acquired a Black Jack Trail Guide II ($99 from New Graham). It's my first convex edge blade, and while I haven't had a chance to put it through all the paces yet, my initial impressions can be summed up in one word: "wow". Man, this is a heckuva knife, especially considering the price. Fit and finish are just excellent and the thing cuts like crazy. I'm going to have to do a little research to figure out how to sharpen it properly, though.
 
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