Thread: Sharpening knives with CBN wheel and strop wheel on slow grinder

Right-on. From memory, Autosol particles are in the range of 3-6 micron; 3 micron is size of the smaller ones.
The Tormek honing paste for leather wheel is the other way - 3 micron is the larger abrasive particles.
Generally, you get shallower scratches and keener edge than might be anticipated for a particular grit size.

It is interesting to see on your illustrations that the scratches from the initial edge-setting still reach the edge apex after honing - every single scratch does, forming a distinctive micro-serration. Definitely to advantage in knives, though the woodworkers would keep honing till the the scratches are smoothed away at the apex.

Certainly those scratches propagating to the edge can be removed by longer and more careful honing. Since this honing is done by hand, I suspect that I set slightly larger angle than I have during original sharpening, and as a result only the very edge is getting honed. If I set a smaller angle, then I would not get edge honed at all.

When I saw a new thread of yours with an attachment, I told myself "Ah-ha, again some good photos from Ilya!" - and wasn't disappointed
Certainly you did hone at some 20+ degree, otherwise you would never get rid of the burr.
If you honed at exactly the same angle you set the edge on the CBN wheel, you would have raised a micro-burr - but on your final photo the edge is almost completely deburred. Well, I can see a tiny foil edge at the very apex, but I have to seriously strain my eyes to see it, and this foil doesn't look as a burr to me, but rather as a stretched apex.

It's similar to deburring by high-angle stopping used by straight razor barbers last century - just they didn't use abrasives on their strops.

The trick is to have that angle increase within the right range, as too steep will round the edge.
We found out the best honing of knives is achieved at +0.4-0.5 degrees, and Tormek sets honing angle at +0.46° on its leather wheel for chisels.
And under the "best" honing angle is meant the best compromise between the time spent and quality of the edge achieved, as if you continue for too long even under this shallow plus-angle, you may eventually round the edge, especially freehand I suspect

I've got a CBN question to you - the leaflet to my CBN wheels says to avoid high carbon steels - the kitchen knives you sharpen on yours are of stainless steel, aren't they?

Thanks, KnifeGrinders, I never knew this about honing, was doing things intuitively.

Some of my knives are no-name and I don't know anything about their steel, but they are softer then my most used - victorinox kitchen knives, which say they are using "high carbon stainless steel". Shown edge is from the victorinox knife.

I though they would be stainless - this confirms our observations that no matter how high carbon contents is, it is OK to grind on CBN as long as the alloy is stainless.
On the one hand, we grind on CBN wheels high-end alloys like M390 or S290 where carbon contents nears 2% w/o issues, on the other 1095 steel with 0.95% carbon plugs the CBN pores.


Thank you for sharing your experience as it contests the general misconception that from that coarse grit straight to honing is too big of a jump.
Obviously, it depends on what abrasive is used for the honing.
Your sequence is a simple yet effective 2-step sharpening routine for mainstream kitchen knives.
We use somewhat similar approach in bulk sharpening for commercial kitchens etc, but using paper wheels with 5-micron diamond paste instead of leather - which shortens the sharpening cycle to under 3 min per blade. Interestingly, I guess 5-micron diamond crystals crashed at high RPM the paper wheel runs at, will give an abrasive mix similar in grit to Autosol you use.

Thanks to your post, I see a microscopical evidence we've been doing it right.

Which Autosol?

Originally Posted by woodPixel

Which Autosol?

It is "Metal Polish" https://autosol.com.au/product-range/metal-polish-75ml/

You can grind any steel on a CBN wheel! I have - O1, A2, D2, M2, M4, CPM-3V, PM-V11.

What you have to avoid is unhardened steel. That will gum up the grit.

Regards from Perth

Derek

Originally Posted by derekcohen

You can grind any steel on a CBN wheel! I have - O1, A2, D2, M2, M4, CPM-3V, PM-V11.

What you have to avoid is unhardened steel. That will gum up the grit.

Regards from Perth

Derek

Much appreciated, Derek

Originally Posted by derekcohen

You can grind any steel on a CBN wheel! I have - O1, A2, D2, M2, M4, CPM-3V, PM-V11.

What you have to avoid is unhardened steel. That will gum up the grit.

Regards from Perth

Derek

Agreed, basically everything except TC

Originally Posted by dai sensei

Agreed, basically everything except TC

Pardon my ignorance, what is "TC"?

Tungsten Carbide

Thank you, Neil.
I guess i know the answer - yet could you confirm - the TC won't gum up the CBN wheel, just a diamond wheel will grind the TC better - is this correct?