Hey fellas. I've been reading some excellent posts here about how to make a convex edge on a knife. I was just wondering, what are the pros and cons (if any) of a convex edge over a beveled edge?

a convex has greater durability over a flat or hollow ground edge, but cannot attain the maximum sharpness of a hollow grind.

practically speaking, most production knives are ground with an edge more obtuse than the convex grinds we apply at home, so there's really no loss. also, grinding a hollow ground edge to the sharpest level attainable is unrealistic since steel ground that thin will not have the rigidity to withstand real use.

The equipment you can buy to sharpen knives is mostly for a bevelled edge and if re-profiling an edge with a view to convexing it it often pays to use this equipment with diamond stones for ease of removal of the steel.

I try to go for the secondary edge at 30 degrees and the primary at 40 degrees as per the Spyderco Sharpmaker which I use after doing this along with a leather paddle strop which I will use to keep the edge.

Once you have this done you can use a belt sander or grit paper and soft surface just to convex the profile from secondary bevel to a true appleseed shape without losing the razor edge gained in the re-profile exercise.

Using a magic marker on the edge after applying it at 40 degrees lets you see how much removal you do at 30 degrees for the secondary bevel. When this profile looks right a quick pass on the belt sander for a couple of strokes convexes the two grinds nicely into a lovely tear drop shape...and you have the advantage of knowing easy touch ups with sharpmaker and paddle will keep the edge for the life of the knife.

When starting out it pays to know the angles you are sharpening at and my experience has shown that if you go for too fine an angle thinking you will get the sharpest edge possible that this does'nt work...it does'nt last and rolls easily...but some guys here just go for an angle based on feel...although they are the most experienced at doing sharpening on convex edges and probably have it "right" anyway. Remember that you always want a steeper more obtuse angle from the flat belly of the blade as it curves to the tip than you have applied to the flat....so as to preserve the strength of the tip...I usually go 50 degrees and 40 degrees on the secondary bevel here...this is the bit most commonly got wrong and you end up with a thin tip.

These angles are based on the Sharpmaker figures...if using Lansky guides remember they give an angle based on an imaginary plumb line going through to the apex of the blade....so 30 degrees is 15 degees and 40 is 25 etc. This can be confusing when you first start out.

Thank you guys. I was planning to use the tutorial for convexing by the bark river knife company website as given by one of the members here. When talking about primary/secondary edges I'm totally lost <img src="/ubbthreads/images/graemlins/paperbag.gif" alt="" /> Is the general concensus to use a system like a sharpmaker or lansky in conjunction with the mousepad and sandpaper?

Yes you can use a Lansky or Sharpmaker in conjunction with a mouse pad.

Primary and secondary edges are best understood as follows-

1/ You get your scrapyard knife which comes with a very obtuse edge geometry. Using the Lansky figures which give an angle measurement based on a single side of the edge - not based on both sides of the edge like the Spyderco Sharpmaker - the edge is probably at 30 degrees....which would be 60 degrees if you go off the Sharpamker's method of showing the angles of the rods when fitted to the given slots...saying it simple...there is two rods on the sharpmaker...so both angles or sides of the edge are included in their standard 30 degrees and 40 degrees slots for the sharpening triangle stones....on a Lansky you use only one stone and rotate the knife....so you have only the angle of one side on the Lansky.

2. The primary edge is the one you sharpen first...it becomes the primary bevel. You start with either 20 degree angle on the Lansky or 40 degree slots on the Sharpmaker. This gives you a standard single bevel edge.

3. To reduce the cutting surface of the edge and assist in slicing...you can add a shallower second bevel or secondary bevel at 15 degrees on the Lansky or 30 degrees on the Sharpmaker....THIS TRIMS THE SIDES OF THE PRIMARY BEVEL....it does not reach the apex of the edge....if an apple seed shaped edge created by a Convex technique is the best shape to an edge...a primary and secondary bevel using flat grind angles is the next best thing...this gives a V shaped grind which has the top bits of the V intersected by a shallower secondary bevel. Hope this helps.

Good explanation Steel Fan, thank you <img src="/ubbthreads/images/graemlins/cool.gif" alt="" />

If I plan on using the sandpaper method at obtaining a convex edge, what is recommended for field use (in the wilderness backpacking etc.) in keeping a convex edge sharp?

Check out this little field sharpener in this thread. Young man by the name of Simon is somewhat of a sharpening savant and he is still in high school. <img src="/ubbthreads/images/graemlins/crazy.gif" alt="" />
http://www.bladeforums.com/forums/showthread.php?p=6184227#post6184227

Now there is a young lad with a bit of ingenuity....the Altoids sharpening kit...I like it!

Personally I use an Eze Lap brass screw diamond hone for the field...it can fit into a loop on your sheath like a fire steel would do. I carry a pipe cleaner which I have cut and folded inside it so that the length of either side equates to the base and opposite sides of a triangle which when folded out at a right angle can be used as a good indication of the proper angle to hold the Eze Lap at to touch up the edge....basically using maths and tangents to determine angles....photo's are probably needed to show this clearly...so I might do some...the easy bit is having some gear that can restore the edge...the hard bit is sharpening at the right angle...my technique and gear works like the sharpmaker system...which I have also packed into my Bergan if I am away for a good while and which like the Altoids tin above...I have glued a leather strop and a mouse pad base to.

I will do some photo's tomorrow....it's dark here now in the UK.

The mini "field" sharpener is a cool idea. I guess I should attempt to put something like that together and give it a try...

Hack again?!

great info guys

Great info! Thanks. This should help alot with my sharpening of the WD.