Thanks Joe, always appreciate your comments.
Rando, I actually wrote a long and involved answer to your questions 2 days ago on my iPad and just when I was about ready to hit the submit button my iPad battery died. It was a great answer, perfectly crafted. It was like running a 3 hour carving project that came out perfectly, flipping it over to add a keyhole and plunging though the face. So it took me a few days to recover from that.
So I will try to answer it again today as I sit here and watch the accumulating snow here in New York.
Yes, the bottom of any plane needs to be very flat, better than the .005", probably closer to .001", especially in the area around the mouth where the blade comes through. And, No, you can't get that on a Shark, but I think I get very close. I use a 1/4' downcut bit and take only 0.050 in Z per pass. The two halves come together very well with the three locating pins, but still not flat enough. I have about 10 or 12 planes of both metal and wood. I flatten them all on a granite surface plate that is probably .0005" flat with a sheet of 220 sandpaper on it. For the maple block plane, this took about 5 minutes. I draw a squiggly pencil line over the complete bottom, then rub away until it is all gone. I keep one perfect straight edge that I purchased just to check things like this and it looks perfect to me, no light. I have not run and indicator on it yet, but I will try that.
Metal planes of the Bailey design have many adjustments to get the blade edge perfectly aligned with the plane bottom. With a wooden plane you use a small brass hammer. Tap the blade to advance it, tap the front of the plane to retract it, tap the sides to change the angle, finally tap the wedge after each adjustment to set it. It takes getting used to but it works well. The point is that the perpendicularity of the blade bed to the plane sole (bottom) is not that critical because of all this adjustability. Blade edges can be out of square also, so many of these variables can be overcome with adjustments. The shark does give a much better locating of the blade bed to the plane sole than other methods of wood plane manufacture.
To help mitigate the Shark issues besides the light passes mentioned above, I have calculated before that the entire bed is about 0.0285" out of flat due to axis deflections on my shark Pro Plus. (see page 2 here for that calculation
http://www.cncsharktalk.com/viewtopic.p ... 0&start=10) so I'm a corner cutter. I don't cut corners, but I keep these small parts located in the lower left corner which lessens the effect of the deflections. I also have a stiffer Z carriage since I rebuilt mine with the aluminum Hangover design discussed here
http://www.cncsharktalk.com/viewtopic.php?f=4&t=4371.
Regarding the finish I haven't seen or felt that effect. Wooden hand planes are traditionally finished with Boiled Linseed Oil which I feel evaporates or absorbs into the wood quickly. I didn't use that on the maple blockplane as I used a wipe on Polyurethane on this one. Also its use is largely concentrated on working end grain, adding corner chamfers, or forming radius on corners, so the surface contact is minimal in these case.
Most woodworkers actually put a light coat of 3 in One oil on the surface of their metal planes to help lower friction. I've also seen paraffin wax used. You don't want to use either of those on you last pass before finishing for sure. I sharpen my plane blades then do a final honing with a 4000 grit waterstone. You can't get that type of surface finish on wood with sandpaper, its stunning the first time you experience it.
I'll add a pic of the plane bottom and see if I can find my indicators.