Fingernail profile on carving gouges?

I am an inexperienced wood carver, but I have accumulated a good number of vintage carving gouges. Attachment 517164
Old tools seem to pile up on my workbench.
A lot of these tools came from two estates, one a violin maker and the other a sculptor.
In both cases about 1/2 of their shallow gouges #6 and below have fingernail profiles.
This seems counter to the advice given on the internet, recommending a straight 90 degree profile for all the gouges.
What am I missing? Is instrument carving that different from general wood carving?

The two gouges on the left were the violin maker's, and the two on the right were the sculptor's.
The two in the center are straight profiles for reference.

I don't know the answer, but I can hazard a couple of guesses. I cannot recall in any old texts on carving, having instructions on grinding with anything other than a straight edge, maintaining sharp corners. But like you I see convex edges all of the time with old tools. Some of these have likely been botched in the grinding by inexperienced hands, but there are so many like it the some of them must've been purposefully ground that way. I can't think of any real advantage to that way of grinding, maybe for stab cuts (like egg and dart molding, for instance, it may help a bit).
So, my guesses are:

The owner used a power grinder and gradually removed the corners by not varying the pressure against the wheel (the corners grind away in a flash). Then after losing a corner, they just 'went with it.' grinding in a fair curve, rather than grinding back straight and losing a measurable amount of blade length each time.

or

When you hold the gouge in carving position, the edge, when ground straight across will be angled in such a way that the corners will be in front of the bottom of the arc. Try this to see. If the edge is ground convex, like all of yours pictured, then if held in carving position, the full sweep of the edge will be presented to the wood more vertically. I am not sure this is a good thing, but maybe it is for some cuts.

I have done the odd bit of lutherie and cannot see why this type of grind would be particularly advantageous, profiling violin backs and soundboards, as well as archtop guitars are really no different from general woodcarving. The gouges in instrument-making are really only roughing tools, the fine work is typically done with finger planes, often with toothed irons for fiddleback maple, as well as shaped scrapers.

Lotta words to say, "huh...beats me..."

DC

I also have no idea why someone would have such a grind on a large gouge. I do have a small gouge with a finger nail grind I use for cutting in brusso quadrant hinges. Maybe someone was thinking of using it for spindle turning?
Good Luck

I have found that fingernail profiles on gouges are very useful in some cases- especially when doing relief carving. At the end of a stopped channel or, with the gouge inverted, finishing the end of a rounded or curved raised area (like an eyeball or a leaf vein) where is joins a flat area, the thumbnail or "nosed" gouge will cut flush to the surface the shape joins without the "wings" of the blade cutting in past the end of the cut. OK, hard to put into words, but take a nosed gouge, turn it over, and touch it to a flat board, tilting it until the whole cutting surface is in contact. You can see that the negative air space between the gouge and the board is what you could shape without overcutting the board below.

Another example is making a fingernail recess to open and close a sliding door: first make the stop cut (preferably with a nosed flat chisel or skew to make it deeper in the center), then with the gouge belly- down, you tilt the back up until the nosed edge looks straight across from above, then make the cut. This allows you to make that almost conical cut with one stroke and without overcutting the sides where it hits to stop cut.

I have a set of old flat crank-necked gouges from a patternmaker's tools and they are all nosed, with the radius of the blade edge matching the curve of the gouge. The grinding was done on a radius (the heel of the grind is consistent distance from the edge), so that professional at least saw a need for it.

I just took a class with Mary May last weekend. She talked about the convex edges and said that in most cases you want flat edges and sharp corners, but some rounded edges come in handy when carving beads, grapes, and similar things. I once bought a set of Pfeil gouges, all straight gouges, 3, 5, and 7s, with widths of 10, 14, and 20mm in each sweep. Every one had the same rounded edge. None looked used. So somebody thinks it's the way it ought to be done.