Help me fix the uneven edge angles on my dull benchmade

[JonM]

I have a very very simple problem that hopefully has a very simple answer. I bought a benchmade 940 about a month or so ago and have been very happy with it in every aspect except for its sharpness. It came to me not sharp enough to shave hair, and it took me several days on a sharpmaker to get it to that point. I attempted to put on a 30 degree back bevel with a 40 degree microbevel. unfortunately, the blade lost its shaving-sharpness over a few weeks of light use cutting up cardboard boxes, paper, and carving wood while camping.

I recently used a sharpie to cover the edge of the blade before using the sharpmaker, and I noticed that while one side had its sharpie removed almost immediately, the other side only had its sharpie removed along the shoulder, leaving the very edge still covered. I initially suspected that I had overdone it with the microbevel, and decided to ditch it in favor of a 30 degree edge, but after literally thousands of swipes on the course stones over a few days, the edge seems to be in exactly the same condition.

This leads me to wonder if I am making a mistake by sharpening both sides equally. In order to correct for the blunter angle on one side, does that mean that I should sharpen only that side until I can take off all of the sharpie before I resume sharpening both sides equally? I have not yet been able to remove

The course sharpmaker stones seem to be almost useless for the task of grinding down shoulders. In frustration with the lack of results I have been getting (I can only shave with pressure, the edge reflects light under a light source, and gets snagged or rips when cutting paper) I ordered a set of diamond rods for the sharpmaker today.

Anyways, I guess I am just looking for any input you guys can give me on correcting the uneven edge angles. I think I am going to ditch the microbevel idea for now (I always fear that I am overdoing it and messing up my edge) and just go for a 30 degree edge. I just want to be able to justify carrying around my 940 osborne, as it is such a beauty of a knife, but I just can see myself doing that when my 30$ tenacious seems to be twice as sharp as it is. As mentioned before, my main question is whether I should sharpen both sides equally when re profiling to 30 degrees, or if I should only focus on the side that is too thick? I tried a search of bladeforums through google, and found several threads about uneven edge angles, but non of them seemed to include step by step info on correcting them, speciffically with a spyderco sharpmaker. Do you guys think that the diamond rods will do the trick when they come in a few days, or is it possible that I am just doing something wrong? Just for backround info, I have used the sharpmaker to get great edges on other knives, especially spyderco's.

Thanks in advance,
JonM

PS. Do you guys know if cutting paper will dull your knives unusually fast? I get knife OCD at times and will sometimes fill up half of a wastebasket with paper ribbons in a night. I will wander around the house half-asleep at three A.M. and cutting up magazines and scratch-paper while intermitantly attempting to shave my leg hair as if cutting up everything in the recycle bin will make the blade sharper.

 

[Jason B.]

Once you get the diamond rods your problems will be over, use them the to set a completely new edge then refine with the other stones and finish with a strop. The brown ceramic stones are not a coarse stone and do not remove enough material to be effective at a reprofile, also how often do you clean your ceramics?

Using a stright 30 will work just fine and when its starts to dull you can do a micro at 40 if you like but there is really no need unless you do heavy work with you knife.


Most factory knives have uneven edges and when using a system that has set angles you must set the knife to the sharpener or like you have found out your edges don't come out like they should.

 

[Roger999]

Keep going on the side that is thicker, when you reach the edge, you can start alternating strokes again, you could try wrapping coarse sandpaper around the rods to speed up the process.

 

[walkingsapien]

You need to create a burr along the whole length of the blade by using a coarse stone on the thicker edge. Once you have created a burr then swap sides and use equal polishing on both sides with a fine stone. You can then add a final micro bevel with a fine/ultra fine, only a couple of runs.

You need to create the burr first.

 

[OldDude1]

Greetings JonM: The 940 is my favorite medium duty knife. I have two of them and have experienced the unequal factory bevels and the less than stellar out of the box sharpness. Both have been used to cut MANY yards of corrugated box cardboard. In my limited experience, this is what I have found: It takes a ridiculously long time to re-profile the s30v steel down to a 30 degree edge using only the medium Sharpmaker stones. Once done however, touch-ups are quick and easy. The factory edge was relatively course and in initial use seemed to be prone to "micro chipping". It seemed to dull quickly for a steel of this quality. After re-profiling and re-sharpening the S30v blade steel keeps an edge measurably longer and the "micro chipping" problem has disappeared. The extreme cutting edge may have been softened by friction generated heat during it's factory belt sharpening. The re-sharpening may have exposed fresh harder steel. For cardboard, a 30 degree POLISHED inclusive edge works quite well for me. The polished aspect may be important. Cardboard, is surprisingly abrasive. Some of us use cardboard as a strop. Recycled cardboard is even more abrasive. It appears to have all the dirt, grit and impurities from it's previous incarnations locked within the fibers of the new box. Some glossy magazine paper contains a type of clay as a finishing agent that is also abrasive. I found the modified tanto blade shape conducive to using only the tip when cutting boxes. This concentrated the abrasion in a small section of the edge resulting in accelerated localized dulling. The rest of the edge was still very sharp. Using the tip to open boxes and the rest of the blade to break them down when empty solved this problem. A re-profiled 30 degree polished edge, cuts paper and cardboard very well, is long lasting and easy to maintain. Don't round the tanto tip by slipping off the ceramic rods. OldDude1

 

[Dog of War]

Good advice given already. I'll just add that something you may want to watch for is the edge being off-center. Unfortunately this can be very hard to tell until after you've reworked the edges to the same angle ... what you'll find is that after you've taken the primary edge bevel on each side to, say, 30 degrees, the bevel on one side may be noticeably bigger/wider than the other. Now, this isn't a big deal in terms of how the knife is going to cut, but on a sweet piece like a 940 it can look kind of, well, you know....

Anyway, you can watch out for this as you're working out the edges, and the thing to do is just start doing more work on the side with the narrower bevel, which will help center the edge to the blade. And over time as you resharpen, if you make it a point to work primarily on the narrower bevel (if this happens; it may not) it will eventually work itself out.

 

[OldDude1]

Thanks Dog of War. I saw this on my BM 930 after re-profiling on a Sharpmaker. I thought it was my imagination. Cool. I learned something today. Thanks. OldDude1

 

[Dog of War]

Thanks Dog of War. I saw this on my BM 930 after re-profiling on a Sharpmaker. I thought it was my imagination. Cool. I learned something today. Thanks. OldDude1

You're welcome, OldDude. We all gotta share, you know: most the world just doesn't understand what it's like to be a blade enthusiast.

 

[Jason B.]

Good advice given already. I'll just add that something you may want to watch for is the edge being off-center. Unfortunately this can be very hard to tell until after you've reworked the edges to the same angle ... what you'll find is that after you've taken the primary edge bevel on each side to, say, 30 degrees, the bevel on one side may be noticeably bigger/wider than the other. Now, this isn't a big deal in terms of how the knife is going to cut, but on a sweet piece like a 940 it can look kind of, well, you know....

Anyway, you can watch out for this as you're working out the edges, and the thing to do is just start doing more work on the side with the narrower bevel, which will help center the edge to the blade. And over time as you resharpen, if you make it a point to work primarily on the narrower bevel (if this happens; it may not) it will eventually work itself out.

Usually when you hit 15 or less per side you will start to notice that a lot of knives have different size bevels, this problem is not with the edge grind itself but the main grind of the knife is not perfect. Sometimes it will just be spots of the knife where the bevel is a different size, If the bevel is larger then the grind on that side is thicker and is the bevel is small the grind is thin.

 

[JonM]

Thanks for all of the great responses! I have definitely learned a thing or two from all of your replies. It is good to know that the sharpmaker is optimal for knives that already have a matching edge geometry. This definitely makes sense as I have been able to get very good edges on my spydercos in relatively short time frames. Once I get the diamond rods and re profile, I expect that it will be a much quicker and easier process to get an edge back on my osborne.

Someone mentioned that putting on a micro bevel only takes a few swipes on the fine rod. I now know that I was going about it all wrong by using dozens of swipes on each rod. It may take a little bit of work to correct this, but at least I may be able to expose better steel in the process. (I also noticed that the very edge seemed a little easy to chip and make course)

Also, you mentioned OldDude, that I needed to be careful not to round the tip by sliding off the rods. Unfortunately, I already have dulled the tip somewhat doing exactly this. Do you or anyone else have any advice on resharpening the tip? I am about do search youtube on the topic and I'm sure I will find some useful info, but it would be cool to hear any advice specific to the sharpmaker.

 

[Jason B.]

At the end of the sharpening stroke stop at the tip, if you do this the not sharp tip will become sharp again.

 

[Dog of War]

Usually when you hit 15 or less per side you will start to notice that a lot of knives have different size bevels, this problem is not with the edge grind itself but the main grind of the knife is not perfect. Sometimes it will just be spots of the knife where the bevel is a different size, If the bevel is larger then the grind on that side is thicker and is the bevel is small the grind is thin.

Yes, it's interesting what all you can discover about a beautiful new blade, once you decide to give it a proper edge. Too bad it isn't as easy to correct for a bad main grind as it is an off center edge. With Benchmades, while I've run into off center edges several times -- few ambidextrous sharpeners at their plant, I guess -- their blade main grinds have generally been good ... but then it's been several years since I had a new Benchmade, so that could have changed.