My edges aren't very good, until I strop, and then they are very good. What's going on?

L

leozinho

Joined
Jan 7, 2005
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Using waterstones, I'm not satisfied with my edges. I can take a simple carbon steel through a full range - Cerax 1k (get a big burr on both sides), Suheiro Rika 5k (faint burr), Kitayama 8k (I don't feel a burr here). Under a loupe the edge looks good. I'm definitely hitting the apex. Sharpie trick shows I've removed all the marker. I draw the edge over the inside of the kitchen cabinet to supposedly remove any burr.

But the edge is meh. Might shave reluctantly. Might not.

Then I can strop, maybe five to 10 passes on each side, and the edges is screaming sharp. Shaves with no resistance. I doesn't matter if I use generic green compound on leather or Shwartz CBN .5 micron on balsa, I get the same results. (Though spending more time with the CBN does improve it even more. I've whittled hair at times.)

I don't think the stropping its self is removing enough metal to explain the improvement. Maybe something to do with the wire edge? I know I shouldn't be moving from the 1k until the edge is better. So I want to do it the proper way.

Thoughts on what I'm doing wrong?

Thank you
 
It's important to know: what steel type are you sharpening? And at what hardness (if known)?

The description sounds like a weak & ductile wire edge that's flipping back & forth. Stropping aligns it, so it seems 'sharp' as long as it's aligned.

After stropping it, try drawing the edge through some wood or heavy cardboard. Cut aggressively into it - don't be shy with pressure. The idea being, if there's a weak wire there, you're trying to strip it away and leave only stable steel behind. Then check for sharpness again. If you notice the sharpness has immediately changed (for good or bad) after a deep cut through the wood or cardboard, that pretty much confirms the presence of a weak wire on the edge. It's also possible, if the edge is fully apexed, that stripping away the wire might also actually improve sharpness somewhat, and make the remaining edge more stable as well. That's ideal, but not necessarily the likely outcome, when trying this.

If you DO find there's a wire edge, go back to the stones again and sharpen as you did before. Then, BEFORE stropping, draw the edge through the wood or cardboard again, check sharpness after doing that, and then go to the strop again. See how or if the results have changed or (hopefully) improved.
 
Obsessed with Edges said:
It's important to know: what steel type are you sharpening? And at what hardness (if known)?

After stropping it, try drawing the edge through some wood or heavy cardboard. Cut aggressively into it - don't be shy with pressure. .
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Carbon steel to stainless up to S35vn- I don't have any real deal super steels. Hardness unknown. (I do notice the green stropping compound doesn't work as well as the various diamond pastes I have on S35VN. No surprise there, I guess.)

I've only lightly drawn the edge through wood to remove the wire edge. I'll use more pressure and see.

Thank you.
 
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What is your sharpening technique? One thing , and a newb myself, I have noticed is the sharpening techniques DOES make a difference. I have seen this from numerous video on sharpening but the Micheal curry video really drove it home. You can sharpening in pretty much any direction you want but before you leave the stone you want to do a stropping process on that stone. Meaning sharpen as you normally do and then before you move you "strop" on that stone. Micheal Curry says its like pushing the knife threw a sand box sharp edge first , its going to dull. Draw the knife back edge first and its going to sharpen the sharp edge. It sounds like the fine edge is laying over and its not until you strop that you straighten it up.
 
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Metal Man 007 said:
I am assuming the 5k and 8 k stones are similar in aggressiveness to the strop.
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I get pretty good swarf on even the 8k. Hard for me to think that the strop is removing nearly as much metal.

If we were talking about a super steel the waterstones couldn't handle, then the CBN paste might explain a jump in sharpness. But I just sharpened a 1055 steel hatchet. Kinda meh until I stropped it on green, and bam!
 
leozinho said:
Carbon steel to stainless up to S35vn- I don't have any real deal super steels. Hardness unknown. (I do notice the green stropping compound doesn't work as well as the various diamond pastes I have on S35VN. No surprise there, I guess.)

I've only lightly drawn the edge through wood to remove the wire edge. I'll use more pressure and see.

Thank you.
Click to expand...

I asked about steel type & hardness, because some of this flimsy wire edge behavior can happen more often with some types of steels. I've seen it in simple carbon steels like 1095 at relatively low hardness (mid-50s HRC and lower), or inexpensive stainless kitchen cutlery at similarly low hardness, for example. Could also be seen with 'better' steels that've had a bad heat treat or experienced heat damage by powered grinding. In cases like that, sometimes the heat-damaged steel can be ground away on the stones in 2 or 3 successive sharpenings, after which the steel at the edge becomes more stable.

But, even simple carbon and low-alloy stainless can escape this behavior for the most part, if heat treat is good and also if the steel makeup itself is of good purity & quality.

Also, if for some reason the sharpening stones or other media aren't well-suited to a particular steel, burring & wire edge issues can be made worse as well. This may not be the case here, but it's something to be watchful for.
 
L leozinho You may want to look at getting new lower grit stones by King they make lower git stones that cut very well and fast.

I think part of your problem is the Cerax and Rika stone,I have the Rika 5k as well and it's not as fast cutting as others I own but for normal steel it should be ok.

Look at the Venev bench stones on gritomatic they are great stones and if you decide to get those try the 100% concentration as well.
 
I have encountered this on some knives where I know I was holding the correct angle and hitting the apex yet it would not slice paper cleanly off my final stone.

Then a couple swipes on basswood with compound and it cuts fine.
I always attributed this to a tenacious burr, I rarely could feel it but something was off.

SAK’s will do this sometimes but not all the time so it may have something to do with heat treatment.

There are so many variables when sharpening and we have to make adjustments to all these things to get that sharp knife.
 
I have run into this before. I looked through my loupe before stroping and I could see the bur that I could not feel. But after a few passes on the strop it looked a lot cleaner and push cut paper
 
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Stropping can explain it without much controversy.
Sight unseen I'm guessing too much applied force on the 8k, and if it is resinoid you might want to try a trailing pass or three as the final step.
 
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