Sharpening carbon steel.

williamsld8

williamsld8

Joined
Sep 19, 2010
Messages
226
I keep reading that carbon steel is the easiest steel to sharpen. I have only owned/sharpened stainless steel blades until now. None of my stainless blades have ever given me trouble once I moved from Arkansas stones to using Norton/store brand Crystolon/Grey oil stones, and then DMT stones. Well after getting a carbon steel knife, sharpening it is proving to be very difficult for me, using either the DMT stones or the oil stones. Yes I said even using DMT stones I am struggling to sharpen carbon steel. Shouldn't carbon steel on diamonds pretty much scrape away like butter on the sidewalk??
 
What kind of carbon steels are you working on? I've done 1095, 52100, 5160, and CPM-M4 and they seem to be quite responsive.
 
i sharpen a lot of knives and some carbon steel knives can be a bear when doing them by hand. the knives i make can take a long time to put the initial edge on even with a belt sander. you might want to try a different method for sharpening like the paper wheels. they work very well and you can go from butter knife dull to shaving sharp in minutes. here is a link to the wheels and a post you might find interesting. http://www.bladeforums.com/forums/showpost.php?p=9207988&postcount=710

what brand of knife are you trying to sharpen?
 
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Diamonds are great on S110V but for 1095 the advantage of speed and edge quality is lost. The fact that the diamonds are going through the steel like warm butter is actually the problem, the depth of cut and excessive deformation/burring will make the edge very toothy and harder to finish cleanly.

The Sic stones won't be all that different, they were made to cut very hard steels so they too will be aggressive on "softer steels" causing difficulties getting that crisp and sharp edge. Something a little less aggressive like aluminum oxide stones, wet/dry sandpaper, waterstones, or Arkansas stones would be a big help in getting a clean and sharp edge.
 
I finish my carbon steel blades (Carbon V, 1070, 52100, W9 (Krupp steel used by Roselli)) on an ancient hard Arkansas bench stone that I inherited from a great-uncle who was a carpenter. It seems to impart a micro-toothy edge that cuts amazingly well.
 
I've had good luck with 1095 on just about every kind of abrasive, from diamonds to wet/dry, King waterstones, Norton waterstones, India stones, SiC.

I can't say for sure what you need to do, only what I do. I always (Heh, heh) use a lubricant. I have had not so good luck putting really coarse edges on 1095, its too prone to what Verhoeven called pressure burring and the normal burrs at 80, 120 220 grit are tenacious (but can be dealt with if desired). In my personal experience it takes from a 600 grit edge on up very well and fairly easily - just beware the burr. This steel can and will hold a burr or wire edge and have you hopping mad trying to get rid of it all the way. If I've raised a burr on one part of the edge but not along the whole length I'll start flipping it side for side anyway just to avoid making it any larger than necessary.

I haven't ever had a real problem getting materials to "bite" on it, but when heat-treated to a high RC it can be as tough as 154cm - so a bit of patience is in order. Even with the diamond stones I use a drop or two of dish soap and a drop or three of water. They're a lot easier to clean and don't require lapping, but even a diamond plate can get loaded up a bit.
 
Which DMT hones do you have (what grit)? As Knifenut mentioned, diamond will be very aggressive on this steel. I've often started with a higher grit (finer), when using diamond on less abrasion-resistant steels. Coarser grits will really chew the steel up, if pressure is just a little heavy. Maintaining consistent angle is all the more important too, as just one pass at a different angle can completely wipe out a previously good bevel. If the blade is relatively small, and you're not trying to completely re-bevel, starting with a Fine grit (25 micron/red) is often as coarse as is needed, and should be done with very light pressure. If you have an EF or EEF DMT, you might even try one of those first. Using the diamond hone with some lubrication (like water + dish soap) can help too, in regulating pressure.

Wet/dry sandpaper, at 400/600 grit or higher, can also work very well. It's still quite aggressive with 1095, and starting at a higher grit will make it easier to get a feel for it, without doing excessive damage. If you're uncomfortable with using diamond, this might be the preferable way to start. Using it wet, on hard backing, will smooth the process, and make it easier to maintain light pressure. I think sandpaper is a great way to 'train' the hands for the right pressure with an edge-leading stroke, as it's very easy to cut or tear the paper if pressure is excessive.
 
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I am grateful for all the input. This all makes a lot of sense. But I should have clarified that the problem isn't that the abrasives are too agressively cutting and. I'm struggling with the edge, I'm struggling to rebevel the blade. And it's a small blade. Using XC, C, or F, I'm getting the same result of the steel just laughing at me after each pass.
 
Is this the Bear & Son folder you posted about in Traditional? With the slight recurve in the blade?

If so, I think the sandpaper on a slightly curved backing would help the most here. Any cylindrical surface, like a jar, PVC pipe, etc. would do for the backing. Let me know if that's the one, and I'll fill in some more details on what you might do.
 
It sure is that Bear and Son little trapper! Good guessing fellas! You're doing great, except I already got the recurve part out of it. Now I'm reprofiling. Problem is I'm watching the scratch pattern and the edge for burrs and everything, I'm seeing no progress. Interestingly enough, when I change abrasives I get a little response. I went from diamond to SiC stone, and got a small change, then plateaued. Then from that stone to SiC paper on hard backing (don't want to convex this) and got a response again, and plateaued. Moved back to diamonds and it reacted again for a bit. This observation baffles me to be honest. Why does it seem to work for a bit, then all of a sudden cross its arms and say "No more"?
 
What grits of sandpaper do you have? I'm still inclined to recommend staying with grits that aren't too coarse, for this small blade. At a minimum, I'd also stick with one abrasive. I don't think switching back & forth between diamond and SiC is doing you any good at this point. A couple more questions, so I have a clearer picture of what you're doing:

1. Are you trying for a shallower (narrower) bevel angle, or are you just trying to recreate the bevel at the 'factory' angle, after straightening out the recurve?
I ask this, because I've often found it much harder to put a really keen edge on the (usually) obtuse/thick factory bevels of small blades. I always try to re-bevel to a shallower angle, as that will make a wider bevel that's much easier to keep in flush contact with the hone.

2. What stroke/motion are you using (sweeping heel-to-tip, circular, edge-trailing, etc.)?
With my smaller pocketknives, I've had good luck using sort of a 'diagonal' heel-to-tip, edge-leading stroke. In other words, I orient the blade somewhat diagonal to the edge of the hone/paper, and sweeping the blade from heel-to-tip. I keep my index finger on the blade, near the heel, to keep the blade in flush contact through the stroke. With the blade diagonally-oriented this way, you're sort of 'pulling' the heel of the blade towards you, as you sweep the blade across the hone/paper. I find this method better for controlling the angle, especially on a small knife.

Some like to use a 'circular' motion on the hone, as it can be a good way to keep the angle more consistent. I sometimes do it this way, especially when initially removing a lot of metal to re-bevel. But this might seem awkward for others, and if so, might create more problems than it solves.
 
I alternate between the diagonal sweeping motion you described and placing the straight edge sideways across the stone and sweeping straight forward and then sweeping to get the belly and tip in at the end. Once I set a scratch pattern using one of these techniques, I'll go to the other if I'm still trying for heavy metal removal. If I'm focusing more on refining I'll stick to the diagonal sweeping. And when I have tried the sandpaper, I use 600 grit wet/dry SiC. I have used the circular motion back when I first got into sharpening, about 6ish years ago. But I didn't care for that too much. I think the thing that has me so troubled is that I'm using the same materials and methods I use on all my other blades, which are stainless, and always with great results. This is the first time I have experienced this.
 
As with my earlier recommendation about sticking to one abrasive type, I'd recommend doing the same with the stroke/motion used. You mentioned earlier, that you can produce an improvement initially, and then it goes away (plateaus). Does this happen when/after switching to the alternate stroke? I ask, because personally, I'd find it very difficult to maintain a consistent angle if I were alternating my stroke/motion. I'd also pay very close attention to when you reach that 'optimum' point, and then STOP. Take a close look at the edge, with magnification, to see what that 'good' edge looks like. Proceed very carefully from there on. Something that helps in this regard, is to continue with the same motion/stroke, but do so with a finer grit at even lighter pressure. When I sharpen, I tend to think of the process as 'sneaking up' on the apex of the edge, just far enough to begin to produce the burr, and then going very, very gently after that, at finer grit and lighter pressure. I suspect that you're overshooting, in a sense, when you've found that your good edge has gone away, all-of-a-sudden.
 
I will probably stick to the diagonal sweeping motion then, as I had a tiny suspicion about this as well. And to answer your question, the plateauing usually happens after sticking with a stroke on one abrasive for a bit and working toward getting a burr, and then realize I have been working for forever and not seen one. Also, that "feel" of the abrasive removing metal (I know you know what feeling I'm talking about ;)) goes away around this same time. Thought it could be loading, but then I clean the stone I'm using and nothing comes off it.
 
williamsld8 said:
I will probably stick to the diagonal sweeping motion then, as I had a tiny suspicion about this as well. And to answer your question, the plateauing usually happens after sticking with a stroke on one abrasive for a bit and working toward getting a burr, and then realize I have been working for forever and not seen one. Also, that "feel" of the abrasive removing metal (I know you know what feeling I'm talking about ;)) goes away around this same time. Thought it could be loading, but then I clean the stone I'm using and nothing comes off it.
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The bolded part above sort of emphasizes what I was getting at, about 'sneaking up' on the apex & burr formation. I think it'd help greatly to stop after every 5-10 strokes & look at the edge under magnification, so you can see when you're getting close to the apex. It may be you are getting the burr, but not noticing it when it happens, and then scrubbing it off.

The mention of 'feeling' the metal being removed reminded me of something. Part of the advantage of taking it very slowly & lightly, is in feeling the edge 'bite' into the hone when the apex is reached. Ordinarily, until that happens, the feeling will seem kind of slippery on the hone. When the bevel is ground down to a point where the edge finally is flush to the hone, the edge will feel like it's trying to 'dig in' to the abrasive. That's the thing to watch for, and the indicator to stop and inspect for the beginning of the burr formation, and then switch to a strategy of very lightly cleaning up & removing the burr.
 
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I think this is what I need. I'm going to give it another shot on the SiC stone, on the fine side. My DMT stones are the diafolds, but the stone is an 8 inch stone I can set down and have more surface area. I'll let you know how it works out.
 
williamsld8 said:
I think this is what I need. I'm going to give it another shot on the SiC stone, on the fine side. My DMT stones are the diafolds, but the stone is an 8 inch stone I can set down and have more surface area. I'll let you know how it works out.
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Your situation has given me an opportunity to check some things. I have a smallish Moore Maker 2-blade double-lockback trapper (by Camillus) with 1095 blades. I also have two DiaFolds (C/F and EF/EEF), which I've set up with my MagnaGuide & Aligner clamp. I'm re-bevelling the smaller blade of the two (a narrow California clip, with a 'hint' of recurve, by the way). Being that I'm using the clamp & guide, I feel I can get a gauge of the aggressiveness of the DiaFold hones, without the added variation in angle distorting my results.

What I mentioned earlier, about the possibility of not detecting the burr when it forms, and then scrubbing it off, is ringing true with my setup. The diamond on these hones is scrubbing metal away from the edge VERY quickly. Knifenut mentioned earlier about the diamonds going through the steel like 'warm butter'. That description is dead-on, based on what I'm seeing here. I mentioned feeling for the edge 'biting' into the hone, when reaching the apex, and I'm finding that just ONE additional pass on the hone, past that point, is quickly erasing whatever burr was forming. I'm finishing most of the work with my EF/EEF DiaFold, just to slow the process a little bit. In your case, I think opting for your SiC hone will will help you here (for now). The diamonds can still be used for jobs like this, but it's critical to make sure pressure is feather-light, especially on a very small blade. There really is a big difference in how much you can 'lean into' the hone, when comparing the diamond hones to other abrasives used on simpler steels.

I'm going to re-emphasize going VERY, VERY light & slow, and checking the edge frequently, with the DiaFolds, if using them on small blades of simple carbon or stainless steel.
 
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