Blade chips when sharpening

B

brasileiro

Joined
Aug 26, 2011
Messages
250
Hi folks.
Im using a homemade sharpening jig and have no problem with some soft steel.
Yesterday I was going to sharp a new blade that I never had sharp before and it constantly chip on some areas when sharpening not a large ship, a bit small but is chip.
Im using diamond stones with no lubricant.
Also I’m using leading and trailing strokes (rubbing).
The pressure is just the weight of stone and arm +- 160 grams.
Should I use just tracking stroke?
Is the slurry (metal dust that stay on the bevel) the main reason for it?
I wash my stones every time I’ll sharp an other blade and clean with brush each pass on entire bevel: I work one bevel from heel to tip and brush the stone and the knife.

Thanks.
 
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What steel is it? Or, if that's not known, what brand/model is the knife? Without knowing the specific steel type or hardness, it'll be difficult to say what's causing the chipping. Even then, it could also just be a bad heat treat for the blade, or damage due to overheating of the steel during grinding, which ruins the temper and may not be fixable.

In very general terms, if the steel is chipping, going finer in grit (try Fine/EF/EEF), lighter in pressure, and maybe wetting the hone with a lubricant of some kind, may reduce the chance of chipping. Very brittle steels (and ceramic blades, etc) will tend to chip more on coarser grit, and more so, if pressure applied is too heavy for it.


David
 
The steel is unknown for me. It’s a Faberware kitchen knife hollow grind.
It also show some rust stain spot. Not deep but oranger at surface.
I know how to clean and storage a blade but aim not the only one who is working with it. So...
7T62o79.jpg

Do you believe 160 grams at 1000 grit is still too much?
Thanks.
 
most kitchen knives aren't high hardness steels unless you search out high end knives ... and most probably sharpen better on a non diamond stones ...

but if diamond stones are what you have I would use the finer grit stones and light strokes ... diamonds don't need much pressure to cut fast and may be what is causing the chipping ... or it may just be a poor heat treat in an unknown knife and steel type.
 
JJ_Colt45 said:
most kitchen knives aren't high hardness steels unless you search out high end knives ... and most probably sharpen better on a non diamond stones ...

but if diamond stones are what you have I would use the finer grit stones and light strokes ... diamonds don't need much pressure to cut fast and may be what is causing the chipping ... or it may just be a poor heat treat in an unknown knife and steel type.
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Well, I’m not using pressure over the weight of the systems arm and hardware.
I have another stones as show in the picture but I like diamond finish.
Maybe I’ll have to come back to ceramic stones and see what happen.
Thanks.
1mRG3l0.jpg
 
I have had a similar problem on cheap knives like that before. Usually is a good warning that the edge isn't going to be stable at the angle you are at. Try increasing the edge angle to 20 to 25 degrees per side. Also use very light pressure when sharpening.
 
Per bluntcut's post above^, flattening the edge to remove the damaged steel and re-setting the bevels might work. It may just be that the existing edge might've been overheated & damaged by some prior resharpening (factory, elsewhere). Removing the damaged portion might get you back into some healthier steel behind the existing edge, which should hopefully be more stable and strong.

As otherwise mentioned earlier, I wouldn't think a Farberware kitchen knife in (what should be) low-alloy stainless should be hard enough to actually chip. They're generally too soft/ductile for that (mid-high 50s HRC), and would much more likely roll or deform (dent, etc) by impact on anything hard. So, if it's chipping now, I'd bet it's due to some grinding/overheating damage done in a prior sharpening of the edge.

Thinking back, I have some older 'inexpensive' Japanese-made kitchen knives that behaved kind of like this, in my first few tries at sharpening them. Seemed to be some weak or damaged steel near the edge, which would just sort of crumble away when the edge was made very thin or fine. After maybe the 3rd/4th complete reprofiling of the edges on them, they seemed to stabilize and finally hold the edge I was trying to give them all along.
 
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Does the hollow grind "fade" near the bolster? Looks like a slope.

That is the fingerprint of really cheap made blades with craptacular steel. Crappy geometry, crappy steel, crappy chips, lots of work to remedy that isn't worth it.

That F brand quality ranges from recycle into paper clips to barely mediocre.

Jim
 
Ok. I’ll try a steep angle first. The original angle is 18.35 dps minus the FFG blade angle. If doesn’t work I’ll try grind the stress area and rebevel it.
 
microtech85 said:
It could be your diamond stone. Inspect the surface for any defects. A bump in the stone can definitely cause that. I had a defect on a dmt stone that was doing something similar.
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I don’t think so because it just happen on this blade until now. The stones are already smooth. But thanks for advise.
 
Spideyjg said:
Does the hollow grind "fade" near the bolster? Looks like a slope.

That is the fingerprint of really cheap made blades with craptacular steel. Crappy geometry, crappy steel, crappy chips, lots of work to remedy that isn't worth it.

That F brand quality ranges from recycle into paper clips to barely mediocre.

Jim
Click to expand...
As you and Obsessed and Cap and Colt told, I’m leading to think like you because I already sharpen a Zwillinger chefs knife a nothing like chip happen.
The chip itself doesn’t disturb my tasks but as I’m in learning curve I’m having to be perfectionist.

Thanks.
 
Notice also how in the hollow grind there are striations almost like a picket fence from whatever they ground it with. Run you nail along it and it feels like a file almost. The chips may line up with the valleys.

Got to smooth it out but again is lots of work on sketchy steel.

Jim
 
This has happened to me twice in about 40+ years, and the chips were much larger, deeper into the edge. Both times it was a chisel grind on diamond. DMT interrupted 600 mesh?

Neither knife was “cheap.” One was Wenger 440C.
Both had larger edge angles, were thicker behind the edge than V grind or double hollow ground.

I had to get them off diamonds to repair—which took a long time.

Hope you figure it out.
 
B brasileiro , sorry to hear about your problems with chipping edges. Nice rig you got there, congrats! Apparently you are already experienced with the rig and everything, hundreds of hours of guided-rod sharpening. Me too. I still use my diamond whetstones (Lansky type) for fast effective grinding of certain blade sections or for reprofiling but i was never happy with their performance as fine sharpeners. I prefer the sharpening performance of my Apex-compatible CN whetstones by Ruixin and Adaee. Nice soft stones. Will not chip the edge unless you accidentally hit the stone against the knife edge hah.
 
me2 said:
Had the edge been steeled with a grooved or smooth steel? That can cause what you're describing.
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Do you mean steeled with steel rod like butcher steel? No, I just sharpened and stroped it. I don’t have steel rod at home. I can’t see any advantage on steeling a blade unless you have a ton of work to do at once and don’t have time to touch up an edge.
 
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