Blades dull after 2 weeks

[Elite Edge]

Good day all.

I sharpened knives at a ghost kitchen two or three weeks ago, and the blades were super sharp when I left. However, the client called to say that the blades were already dull. Is this possible at all? They are cutting on food-grade plastic cutting boards and boneless chicken breasts and pickles only.

He says they are currently stored in a bucket after washing but gently placed into the bucket

That is about as much info as I can get. Any suggestions? Would greatly appreciate 

Can my sharpening angle have anything to do with it? I tend to give commercial knives a wide angle of 60 degress total, 30 each side to make sure the edge is not too fine to last longer and used the 220 stone grader to give the blade more bite

[Herman Trivilino]

Are they using a honing rod to refine the edge? They should be doing that on a regular basis. I hone mine every time I use it. I've heard good things about ceramic honing rods.

You might want to talk to other restaurant managers to find out how often they have their knives sharpened, and what practices they use to keep them sharp. Certainly the knives should never be washed in an automatic dishwasher. I knew a sushi chef who sharpened his knife at the end of every shift.

I'm guessing that you might want to lower the angle to 50^o, as 60^o seem too blunt.

[Elite Edge]

Thanks so much, at 60 degrees they were super sharp and passed paper and thumbnail test.

[kwakster]

From your post i would say that it's the overly large edge angle, although the type of plastic the cutting boards are made from could also play a role.

In contrast to what most people think a narrower edge angle lasts longer (within reason)

What i've found is that many generic stainless steel kitchen knives can handle a sharpening angle of ~25 degrees inclusive (when used with care for some time on a reasonable quality cutting board), which if then deburred on the Tormek leather wheel their apex will come out at ~30 degrees inclusive due to the "give" in the leather wheel, which will micro-convex (and thus strengthen) it just enough.
If however i find that my customer is an ignoramus/brute/Shrek/idiot then i increase my sharpening angle to ~30 inclusive,of which the apex will measure ~35 degrees inclusive after deburring.

My own rule of thumb: (the edge should be) as thin as possible, but thick enough.

The knife wielder can then use a good quality (mirror-) steel on that edge, and later maybe a good ceramic rod to prolong the knife's useful sharpness before you get a new request to perform your magic on the knives again.

The happiest customers are those that need your services the least, but most likely they will be your returning customers

[Elite Edge]

Thank you

[3D Anvil]

Yes, I agree that the very high edge angle is the cause of rapid dulling.  An edge bevel is essentially a triangle, with the acute angle forming the apex.  The wider that triangle is, the faster the apex will widen out through abrasion. 

On the other hand, a very thin triangle is more susceptible to rolling and chipping, so you have to balance acuteness versus edge stability.

Personally, I use 15° per side for most kitchen knives, but I know many pro sharpeners do 17°, and some go as low as 10-12°.  It's something I'd explore with your client.   

[tgbto]

I concur with 3D Anvil and kwakster.

The late Wootz, in his research, found that the highest edge retention comes with the lowest angle the knife can handle while not failing. Of course, an acute angle means risks of chipping with hard steels (and low resistance anyway to lateral damage on softer steels).

15dps (30° inclusive) seems to work a treat with most knives.

[John_B]

14-15° per side is how most knives arrive from mainstream manufacturers. Flexible filet knives often are near 11° and need the Long Knife Jig. I normally use these angles and hone at 1.5-2° more. Proper daily care will also extend the time where the blade has acceptable sharpness.

[Ken S]

When I was designing the kenjig, I asked Stig of Tormek for advice for a "one size fits all" angle setting. He suggested 15°.

Ken

[RichColvin]

I would also explore how they use the knives on the cutting boards.  In particular, do the sweep the cut parts with the cutting edge up or down.  It is very common to not flip the knife, and sweeping the board with the cutting edge down will quickly dull the knife.