Convexing another!

TheKallumS

TheKallumS

Joined
Dec 17, 2012
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296
I convexed my Buck 110 and that thing is wicked, insanely sharp. I started to convex my Benchmade Mini-Barrage and it feels sharp, but it doesn't cut very well. I adjusted the angle, of course, and I went at it. The first, I was going faster than I should and it turned out horrible. I went at it for the second time and it turned out better, but it still isn't quite as sharp as I want it to be and NOOOO where near my 110.. I start on 120 grit, go to 220, then 400w/d, then 1200w/d and stop on 2500w/d grit. I strop on a rough leather belt then finish the knife on a green compound treated leather belt. What can I do to get it even around close to my 110. The Buck is 420HC steel and the BM585 is 154CM. I use a tile pad rather than a mousepad because it is think and it can hold down the paper on one end. What should I try? How can I change to get my BM sharp(er)? The edge is polished, but cuts only with lots of pressure, though my Buck glides and pops hair so easily.
 
154CM is more wear resistant that 440 so that could be an issue. (You not taking enough steel off with each grit.)
 
The BM is likely a thicker blade grind than the Buck. Buck's saber/hollow grind blades have typically been ground very thin (near the edge) in more recent years. And as mentioned, Buck's 420HC is much less wear-resistant than the 154CM. The combination of simpler steel and the thinner grind will indeed make the Buck much easier to sharpen.

It's possible the factory edge angle on the BM is also much wider (more obtuse) than the Buck's factory edge (spec'd at 26-32° inclusive on more recent knives, since about 2000 or so). Combined with the thicker overall blade grind, that means much more steel needs to come off the edge of the BM, to achieve results similar to the Buck blade.

Bottom line, it'll just take more time and a lot more patience, with the BM. Make sure to work up the burr with the coarsest grit, before moving to the next grit. Not sure how soft/firm the 'tile pad' is, but using a firmer backing under the sandpaper could help improve things as well. Firmer backing will make the abrasive work a little more aggressively, and will also reduce the chance of rounding/blunting the edge.


David
 
I switched up back to the mousepad and table and I went at it for the third time. I can tell this has took away a lot of metal because there was a chip and in the edge and now it's gone, but anyways. I took more time and looked for the burr and I finally achieved a small one and I went slow and went to a flatter and deeper angle. It curls receipt paper now. Good and very sharp. I should have went slower and longer(that's what he said... LOL) the first time and I wouldn't have ended with two bad jobs.
 
I've found varied results as well with convexing knife edges, some I've done ended up :thumbup::thumbup: and others were :foot::thumbdn:.

It definitely takes patience and dedication to make it happen consistently; and go slower and longer. :D:cool:
 
I have found convexing a knife has extremely varying results. I sent a knife to Richard J to be convexed and his edges are the bomb! I since, have liked convexed edges. I have a few knives V grind, but more that I have now convexed.
 
Yeah, anything sent to Richard J should come back pretty sharp... ;):D

I'm stil learning the whole "sharpening" thing especially with some of the higher end steels; it's a neat hobby in itself to embark on.

Some edge pics, just for fun:


Paper wheel edge:

IMAG0660.jpg



Edge Pro:

IMAG0426.jpg

IMAG0403.jpg



Mild Convex (needed to be polished still):

IMAG0394.jpg



Convexed & polished:

IMG_5924_zps51d3fc32.jpg



Covexed S90V Millie

C360_2012-08-15-17-00-17_org.jpg



All this sharpening & convexing talk reminds me, I've got an SNG that needs to be convexed LOL! :thumbup:
 
His edge work is awesome! I'm still practicing to get it down but it is getting to where I know where I want me edges. I started this morning out with a few knives. The whole polished edge thing isn't my thing. I like a more toothy feel to my edges. May not last as long, but I am okay with sharpening some more. :)
 
I completely understand why folks don't like polished edges and have definitely found that a highly polished/refined edge can tend to "skate" when used against many materials being encountered in day to day use, specifically when doing draw cuts.

I'm still trying different sharpening combinations in terms of polished versus toothy (aka less refined) edges to draw my own conclusions as to which I prefer or what works better. :D
 
When I had a polished edge on my BM585, they would shave hair, but when it came to cutting up cardboard it suffered. I turned back and went back down to 400grit, then up to 600grit and I stopped there. I found that it's sharp and toothy. I haven't stropped it yet. I don't know if I want to. My BK2 has a polished convex on it and I am thinking of putting a rough edge on it as well. The polished edge on my 110 with go through everything, so I am going to keep it as is.
 
The more 'polished' the bevels become, the more important the crispness and purity of the apex becomes, along the full length of the cutting edge. IF the apex is crisp & pure along the full length of the edge, the more effortless cutting will become, either push-cutting or slicing. A polished edge that 'skates' across a material being cut, is more likely skating because at least part of the apex has been somewhat rounded off in polishing (stropping with too-heavy pressure, or on too-soft substrate, or at a too-steep angle). If care is taken to avoid that on a polished edge that push-cuts well in all portions of the cutting edge, the slice-cutting will take care of itself.

One of my best cardboard-cutters is a Buck 112 (440C) that's been convexed & thinned near the edge, with the convex polished to above 2000 grit (mirror/near-mirror). The clean apex is what initiates the cut with minimal effort, and the slick & polished shoulders of the convex offer minimal resistance as the blade goes deeper into the material. That makes for 'scary-slick' cutting.


David
 
As posted by OWE : "That makes for 'scary-slick' cutting."

Hey David, I like that phrase better than "scary sharp", as it is much more descriptive and full of action. For my uses with my knives, a better plateau to reach than just scary sharp. Great choice of words!:thumbup:

Blessings,

Omar
 
OHALLUM said:
As posted by OWE : "That makes for 'scary-slick' cutting."

Hey David, I like that phrase better than "scary sharp", as it is much more descriptive and full of action. For my uses with my knives, a better plateau to reach than just scary sharp. Great choice of words!:thumbup:

Blessings,

Omar
Click to expand...

The 'scary slick' impression came about the first time I tried that convexed & polished Buck 112 on a cardboard box. The blade went through it like it was greased, and it actually spooked me a bit. I made a mental note to myself, from then on, I'd have to be absolutely sure to keep my hand/fingers out of the path of the blade (always a good idea, but I'd occasionally been a little lax with that when using other blades for the same task). :)


David
 
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