Convex edge sharpening and reprofiling question

[thombrogan]

From all of the talk about 52100 and Buzzbait's suggestion about putting wet/dry paper on mousepads, I want to know:

How does a guy without a slack-belt grinder resharpen a flat-ground blade to a convex edge?

Would you triple or quadruple bevel it and then go to the wet/dry papered mousepad to finish up and smooth out the edge?

Also, when sharpening with a charged mousepad (gosh, I feel I've entered a new depth of weird), do you push slightly into the pad and pull the blade away or what?

I just got my book and guides from RazorEdge Systems and believe that could make a pseudo-convex edge with the guides (I can't sharpen, but I'm out to mimick the greats nonetheless), but don't know how to finish the job.

Thanks for reading.

 

[Don Luis]

I had an old Hi-Carbon Barlow with double bevels at 15 and 20 degrees. I just worked it on a mousepad with 320 grit sand paper, raising the spine just a little bit (didn´t want to scratch the blade) with little pressure spine first and it got a convex edge in a few passes, then I used 600 and 1500 grits and strop to get it scary sharp.

 

[Cliff Stamp]

thombrogan :

[without a slack-belt grinder - resharpen a flat-ground blade to a convex edge]

Would you triple or quadruple bevel it and then go to the wet/dry papered mousepad to finish up and smooth out the edge?

The easiest way is to let it happen naturally. Every time you sharpen with sandpaper on the mousepad the edge will take on a more convex shape. As this happens you can press lighter and lighter as the shoulder gets reduced. In the beginning you might want to use a marker on the edge to insure you are using the right force, but the technique is very forgiving and you don't need to be very exact.

If you don't want to wait, then yes, just apply a more acute edge bevel than the existing one and cut down on the shoulder of the current edge. This assumes of course you want the convex edge to be more of an acute profile than the existing one. If you want it to be thicker than you would apply a more obtuse secondary edge bevel and press down hard on the mousepad when sharpening. The more you press down, the more extreme the curvature you will get.

... do you push slightly into the pad and pull the blade away

Yes. This can be prone to high burr formation though, unless the steel is hard (60+ RC) and fine grained (which 52100 is usually though). You will want to use high quality sandpaper and clean it so it doesn't get excessively clogged. You can just brush or blow the grit and steel dust off periodically.

If you do get large burrs you will want to stop after you switch abrasives and do a very light edge leading stroke at a slightly elevated angle to remove the burr. This is generally only necessary after the first coarsest paper, unless the steel is soft and coarse grained.

-Cliff

 

[thombrogan]

Thanks Luis and Cliff!

I'm actually going to do this to an M2-bladed Nimravus, but I want to own a Marbles or a Blackjack, soon, too.

Thanks so much!

 

[Cliff Stamp]

M2 is a very difficult to machine steel, much more so than 52100, but isn't very prone to floppy burr formation. It will take some time to get into the proper shape but the actual sharpening will be fine as the edge should form crisp and clean.

-Cliff

 

[thombrogan]

That's very heartening. Soon, I'll have the ultimate kitchen knife. Impervious to everything but moisture!

I've actually developed floppy burrs with M2 using my Sharpmaker on my Nimravus, Nimravus Cub, and Ares 730CFHS. Maybe it's the curse of the Angry Allen, but I think that's pilot error and too much force on my part.

 

[Cliff Stamp]

That is probably characteristic of Benchmades heat treating rather than M2. There are lots of other things that can induce burr formation though such as clogged or worn hones, and pressing too hard. You have the match the force to the steel. The soft and easy to machine ones demand a very light touch. M2 should never fall into this class though, it makes no sense to heat treat it in that manner.

-Cliff

 

[thombrogan]

That'd be from pressing too hard. I scraped the diamond coating free from their metal Sharpmaker sleeves, so the burr problem was probably a result of pressing too hard. When I reprofiled another M2 Benchmade, I used lighter force and had much better results.

Now to get me some wet/dry paper and some extra mousepads.

Thanks again!