Is there any functional difference (not related to things like embedded diamond grit) between a smooth-surfaced knife (or honing) steel, and one that has visible ridges? Would there be any reason to prefer one over the other?
Clarification: the type of answer I am looking for actually addresses the effect (or lack thereof) of the ridges at the microscopic scale where honing takes place.
I understand that the ridges just make the honing process faster
You can hone a knife with more or less anything. Preferably with material of a similar nature so as not to "grab" the knife edge and pull chunks off it
For a quick test, take a knife that needs honing, and use the back square edge of another knife to hone it with
The square edge bites into the burrs faster than a round edge, but can also "grab" and damage the edge
Honing is a gentle process, you are straightening the edge, and removing burrs, not really grinding the edge
Honing with material that is softer than the knifes edge, will just take longer, but generally produces a better result
The same processes are happening when a barber runs the blade over a honing leather strap, particles in the leather gentle grab the edge, and straighten it out. Any bad burrs will catch on the leather and be torn off
Keep in mind that a knife steel or a honing steel does not actually sharpen the knife, it merely re-aligns the microscopic sawtooths/burrs created on the edge of the knife from cutting to reduce the drag.
The contact point of a ridged-steel is less blunt (smaller radius on the ridge vs the steel) and might deliver more concentrated force.
with a ridged steel you can rest the knife blade and run across two adjacent ridges (creating straight contact with two small surfaces) and reduce the risk of damage (by bending the burrs the other way). a round-steel contact point would be more blunt. (we've looked at the honed edges under a stereomicroscope).
In my experience the ridged steel works better at aligning the burrs (or sawtooths).
To create a new edge or actually sharpen the knife you'd use something like a whetstone or a strap, or even high-grit (>2000) sand paper. By removing the burrs this way, you create a smooth (new) edge.
The ridges on a honing rod provide greater curvature at the point of contact between the rod and the blade. This has the effect of increasing the contact pressure (force is concentrated over a smaller arc).
Some reasons you might want to increase contact pressure:
Reasons for not using ridged rods (ie decreasing contact pressure):
Honing is a process AFTER the Stone has done it's work.
There are around, basically 4 levels of hone.
I use 600 grit Diamond. Followed by a smooth to the touch 15 yr old diamond. by a Ceramic .
I also have a $250 Butchers steel\diamond\? which is 21 1\2 in wide tapered to the sides and used. I believe on the long knives.
My first steel was a "steel" steel with lines all round, down it. I spent a month with a file then sanding papers than a smooth steel till it was like glass. Still have it 50 yrs later. and next to my 50 yr old ex army mule strap Strop. Gives my knives the BEST edge.
If you going to use a steel Use several grades of diamond ones then a ceramic or old leather belt (strop) to finish them off. Mine get the stone about twice a yr. Maybe. The diamonds do a magic job on a GOOD knife. Wustof. Kershaw. Torejo. etc. I don't know that I'd use them on real Damascus blades though?.
The Japanese blades are that hard they virtually impossible to sharpen with normal gear.
