I've been getting in some shop time recently 
rehabilitating/restoring/sharpening & tuning my bench planes - woodies, 
Stanleys & a couple of infills. I'm using tips, ideas and jigs from the 
likes of John Manners, Brent Beach & B Passaro to improve the way my 
planes perform, and I'm getting some very encouraging results! I found I 
can reliably get very fine shavings on the order of 0.001" (the limit of 
my dial calipers) on straight-grained rosewood, from several planes - an 
unprecedented precision I'll never likely need. Interestingly, none of 
the planes exhibit the "tight mouth", "superfine slit" or "fine shaving 
aperture" we read about in books, magazines, adverts and websites. The 
tightest fixed mouth I have on a bench plane is on a infill panel plane, 
about 0.053" parallel to the cutter. I consulted with one of the 
porch-dwellers recognized for his knowledge on such things, and he 
offered the advice that  '0.02" is where I would want to see it at its 
absolute max'. I have to bow to his superior knowledge and experience 
with such things. Presumably the difference between my plane & his 
recommended value is going to make a big difference working bird's eye 
maple and other gnarly stuff, and when planing 'uphill'- what Jeff 
Gorman refers to as 'tear avoidance'. That's when I'll have to resort to 
a scraper or scraper plane and others with tighter mouths can keep planing.

Yesterday I got hit with a cold, so I've stayed out of the cave. I was 
interested to see what others recommend for tightness of mouth, so I 
pulled out some books, searched the oldtools archive and a few relevant 
websites, and found - nothing. Everyone I checked - including Dunbar, 
Bill Carter, William & McConnell (Old Street Tool) - agree a fine, tight 
mouth is an important factor in bench plane performance. But none of 
them seem to quantify their recommendations, which I find more than a 
little surprising. Can anyone shed light on this? If I were to go 
shopping for a top-line  smoother (a fantasy of mine) - vintage or NIB - 
how tight should the mouth be so I can handle whatever tricky wood 
crosses my path? Inquiring minds and all that...

Don
-- 
I have tried too in my time, to be a philosopher; but I don't know how, 
cheerfulness was always breaking in. - Oliver Edwards
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