9CR13MOV and sharpening

B

Bugout Bill

Joined
Jan 2, 2013
Messages
1,508
I've been slumming lately in my knife purchases, and my most recent acquisition was an Inron MY803. It proved to be a fairly nice knife, lockup was good and fit and finish was decent. I was fairly unhappy with the edge, though. I made the perhaps unwise choice to re-profile the knife to 30 degrees by free-handing on the brown sharpmaker stones. After doing what I think was a half decent job at re-profiling it, I used the Sharpmaker to put a 30 degree edge on it.

After going from medium to fine, and then stropping the knife, the edge is no better than the factory one. What happened? Did I mess up the edge, or does 9Cr13MOV simply not take that good of an edge?
 
Personally, I'd find it very challenging to re-profile any edge on the ceramics alone, as with the Sharpmaker. So many passes have to be made to remove that much metal, and more passes usually means (for me) more inconsistency creeping into the process. Very hard to maintain consistent angle and pressure throughout that span of time & effort, and a rounded apex is almost always the result. It's a lot easier to quickly set a clean & crisp bevel on an appropriately coarse stone, forming the burr in the process, and leave the refinement steps to the Sharpmaker. If done this way, bevels are usually a lot more uniform, and there's much less chance of rounding off the finished edge. I'm betting this is what's getting in your way here. The Sharpmaker is at it's absolute best when it's used as a refinement tool only, after a good, crisp set of bevels are already set.


David
 
Obsessed with Edges said:
Personally, I'd find it very challenging to re-profile any edge on the ceramics alone, as with the Sharpmaker. So many passes have to be made to remove that much metal, and more passes usually means (for me) more inconsistency creeping into the process. Very hard to maintain consistent angle and pressure throughout that span of time & effort, and a rounded apex is almost always the result. It's a lot easier to quickly set a clean & crisp bevel on an appropriately coarse stone, forming the burr in the process, and leave the refinement steps to the Sharpmaker. If done this way, bevels are usually a lot more uniform, and there's much less chance of rounding off the finished edge. I'm betting this is what's getting in your way here. The Sharpmaker is at it's absolute best when it's used as a refinement tool only, after a good, crisp set of bevels are already set.


David
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Thank you for the imput. I'm still very much a novice to freehand sharpening, so I'm sure plenty of inconsistency crept into the process. The Sharpmaker is the only real sharpening resource I have at the moment, other than a brick. I probably bit off a bit more than I could chew, but the knife is still respectably sharp.
 
Bugout Bill said:
Thank you for the imput. I'm still very much a novice to freehand sharpening, so I'm sure plenty of inconsistency crept into the process. The Sharpmaker is the only real sharpening resource I have at the moment, other than a brick. I probably bit off a bit more than I could chew, but the knife is still respectably sharp.
Click to expand...

If you're relatively comfortable with the Sharpmaker, and would like to continue to rely mainly on it, you might pick up some medium or coarse grit wet/dry sandpaper; something like 220-400 grit. Many here have used the sandpaper stuck to or wrapped around the Sharpmaker's rods to provide the extra coarseness needed for re-bevelling blades. The sandpaper is the silicon carbide type (3M and Norton are both good brands), and it will handle the 9Cr13MoV easily. When money's limited, the sandpaper is an easy solution if you don't need to re-profile very often. It works even better if firmly stuck to a hard backing (more like a stone), so using some light or temporary adhesive on the back of it is helpful.

Another option that's not too expensive, is to use an angle guide on your blade, like DMT's Aligner clamp ($10-$15). Used in conjunction with a simple coarse/fine bench stone (maybe silicon carbide or aluminum oxide), it's an easy way to set some quick bevels for a new edge. The Aligner clamp works GREAT in this fashion, and it takes the variability out of angle control. That'll go the furthest in ensuring the finished edge will be as sharp as possible.


David
 
Obsessed with Edges said:
If you're relatively comfortable with the Sharpmaker, and would like to continue to rely mainly on it, you might pick up some medium or coarse grit wet/dry sandpaper; something like 220-400 grit. Many here have used the sandpaper stuck to or wrapped around the Sharpmaker's rods to provide the extra coarseness needed for re-bevelling blades. The sandpaper is the silicon carbide type (3M and Norton are both good brands), and it will handle the 9Cr13MoV easily. When money's limited, the sandpaper is an easy solution if you don't need to re-profile very often. It works even better if firmly stuck to a hard backing (more like a stone), so using some light or temporary adhesive on the back of it is helpful.

Another option that's not too expensive, is to use an angle guide on your blade, like DMT's Aligner clamp ($10-$15). Used in conjunction with a simple coarse/fine bench stone (maybe silicon carbide or aluminum oxide), it's an easy way to set some quick bevels for a new edge. The Aligner clamp works GREAT in this fashion, and it takes the variability out of angle control. That'll go the furthest in ensuring the finished edge will be as sharp as possible.


David
Click to expand...

Thank you for the advice, I'm gonna have to take a look at the DMT aligner clamp. I've got a knife on order that is going to need re-profiling when I get it, I was more using the Inron for practice. How good of an edge does 9CR take, though? Is it closer to 440C than 8cr?
 
You might try laying the stones flat on the underside of the sharpmaker and sharpen freehand. Lay the bevel flat on the stones with the edge towards you and use edge trailing strokes. Not to much pressure and keep the edge perpendicular to the ends of the stones. Tip to heel or heel to tip. I find it a bit more comfortable to work with the stones across the body left to right as opposed to pointing away from you.
 
I have a blade with the 9CR steel that is sharp enough to push cut phone book paper without any sound or any rough edges on the paper. In other words, it is SHARP! It holds its edge very well, and when it does need re-sharpening, it is quite easy to do, and a lot of times all it takes is a good stropping with some green compound. Your knife steel is not your trouble. OWE gave some great advice about what happened to your blade. Hang in there and Good Luck.

Blessings,

Omar
 
pjwoolw said:
You might try laying the stones flat on the underside of the sharpmaker and sharpen freehand. Lay the bevel flat on the stones with the edge towards you and use edge trailing strokes. Not to much pressure and keep the edge perpendicular to the ends of the stones. Tip to heel or heel to tip. I find it a bit more comfortable to work with the stones across the body left to right as opposed to pointing away from you.
Click to expand...

This is actually how I did it. It worked ok, I know I removed metal, but I don't really think I re-profiled it that well. I'm going to look into getting the DMT aligner clamp and a cheapish bench-stone like OWE recommended. I don't really trust my freehand abilities well enough to re-profile without a guide. The fact that I scratched up the blade a little has me a little irritated though. They scratches aren't too bad, but will metal polish be enough to remove them?
 
Keep working at it. Freehand skills come with practice. One day the light bulb will go on in your head and it becomes second nature. Scratches happen. You could try to polish them out. If its a big concern going forward use some masking tape to protect the blade. Use the sharpie trick on the blade for reference. An old and cheap method for angle consistency is to glue some pennies together and lay the spine on top of them to use as reference . A stack of two, three and four should do it.
 
pjwoolw said:
Keep working at it. Freehand skills come with practice. One day the light bulb will go on in your head and it becomes second nature. Scratches happen. You could try to polish them out. If its a big concern going forward use some masking tape to protect the blade. Use the sharpie trick on the blade for reference. An old and cheap method for angle consistency is to glue some pennies together and lay the spine on top of them to use as reference . A stack of two, three and four should do it.
Click to expand...

I used the sharpie method and that seemed to work.
 
Bugout Bill said:
Thank you for the advice, I'm gonna have to take a look at the DMT aligner clamp. I've got a knife on order that is going to need re-profiling when I get it, I was more using the Inron for practice. How good of an edge does 9CR take, though? Is it closer to 440C than 8cr?
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I have several blades in 8Cr13MoV (from A.G. Russell), and they take great edges. Assuming a good heat treat and a reputable maker, I'd hope the 9Cr would be at least as good. Should be higher carbon content (better edge-holding) than the 8Cr, and closer to 440C in that respect. So, I'd expect it to be pretty good. I'd assume it should be a bit easier to sharpen than 440C, which has a little more carbon and very high chromium (16-18%), compared to ~13% chromium in the 9Cr13MoV. The extra carbon + chromium in 440C will form more carbides, which tend to make the steel more abrasion-resistant, and therefore a little slower to sharpen up (though with today's tools, even 440C isn't very hard to sharpen).


David
 
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