Bevel angle vs sharpness

[SteveG]

Welcome to the forum Mr. Steve.
 
I’m sure you will enjoy your PT50!  It’s amazing how informative the thing is.  I sharpened for years without one, and now I would feel lost without it.
 
Everything you say makes sense to me.  Subjectively people do indeed say a thinner bevel cuts better or at least requires less effort to make the cut.  From my experience nothing beats a thin blade with an acute bevel for ease of cutting, and it makes sense for the reasons you speak of. 
 
I’m wondering something slightly different and that is the sharpness of the edge without consideration of the ease of cutting something.   I’m pretty sure that the answer is going to be above my pay grade, and has something to do with the properties of steel or something along those lines.
 
My suspicion is that for any particular type of steel there is an optimal bevel angle at which the edge can be the sharpest, i.e. thinnest.

Just curious- what kind of stuff do you sharpen?

Thanks for the warm welcome!

I've only had the PT50 for one day, but I anticipated how useful it would be, and I'm overjoyed with what I'm seeing so far - having numerical feedback instead of subjective is incredibly helpful.

I'm a woodworker, so I mostly sharpen plane blades, chisels, lathe tools, and that sort of thing. I don't have any problems there, either with jigs or freehand, as far as my own needs are concerned. But I have several carving tools which I normally just strop, but are getting to the point where they need more than that, and I question my freehand skills. I also have a few knives, which I also sharpen sometimes with jigs, sometimes freehand. The freehand isn't too consistent, but it doesn't bother me as far as the usefulness of the knives, but I'm determined to improve my sharpening skills, hence the PT50.

I believe you're right about the steel making a difference, as far as the minimum width/radius you can theoretically achieve on an edge.  I think the grain structure makes a difference (on my woodworking tools, I can get O1 sharper than A2, using the identical jigs/methods - that's been a subjective judgement until now, I'll need to prove that with measurements soon).  I have also read that some carbides, notably vanadium carbide, have grains over a micron in diameter, so they're fairly easy to tear out when honing or polishing with grits larger than that, and impossible to reduce with finer grains unless you're using something harder than the VC, such as CBN or diamond. But I'm still not clear how the geometry fits in. There's a lot to learn, and every time I start to think I "get it,' I find something that tells me I clearly don't.

In woodworking, the bevel angle is more a function of use than of the steel (then again, there are only a few steel types most woodworks deal with). For hard use (chopping), big angles.  For paring, small angles. The second consideration is the wood (soft or hard).  Pretty simple until you start carving, or something like that.