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265121 Thomas Conroy 2018‑02‑13 Re: Leather paring and knives, was: Strop
Claudio wrote:  "Re the knife used in these videos reminds me of the ones my dad
used in upholstery.  He copied an old Osborne one, making his own from discarded
Swedish steel metal cutting saw blades from a metal shop (I’m pretty sure these
were high carbon steel, not high speed steel).  These metal cutting blades were
about 1.5” by 24” and maybe 1/16”  thick and he would cut off a length,  grind
off the teeth and then make similar single bevel knives like those shown in the
video.  Watching these videos brought back memories of him showing me how to
work leather, button tuft diamond patterns, turn corners..."

Machine hacksaw blades were particularly favored paring knives and lifting*
knives by the generation of English binders who taught many of my generation of
Americans. They were mostly born around 1935 and trained in seven-year
apprenticeships or in comparably rigorous art school courses. The preference was
not just for machine hacksaw blades, but "pre-war" blades, which were said to
take a sharper edge and hold it longer than any other form of knife. I suspect
that they were finding high-carbon-steel blades, though these would have been
obsolescent in America by the 1930s.

Until quite recently lifting knives couldn't be bought; you had to grind your
own. I've made them, for myself and for half-a-dozen or a dozen students, from
old trashed hacksaw blades (25 cents with luck, but more often a dollar now);
from new Vaughan English "all-hard" or "high speed steel" hacksaw blades (the
markings differ, but they seem to be otherwise just the same); and from new
Starrett "Red Stripe" HSS blades. The first step is to snap the (12" or 14"
long) blade in half, and with an old hacksaw this will tell you if you have a
good single-steel blade or an unusable bimetallic blade. The good blade will
snap cleanly with a fine-grained crystal surface on the break; a bimetallic
blade will snap cleanly in the eight inch near the teeth, but the rest of the
width will twist and deform before breaking. My favorites are the old blades,
but this may be partly sentiment. The Vaughan blades are good, a bit hard; the
Starrett far, far too hard for this use, since it is extremely tedious to
resharpen them. Lifting the leather on the side of the book, you are cutting
through highly-abrasive binders' board, full of trash and impurities, and you
may lose the sharpness of the edge in lifting four inches; so you go through
three blades lifting on one board. Not to speak of 19th-century board, when it
was sold by weight and some manufacturers would throw sand into the pulp to
increase the weight. Fortunately, a highly refined edge isn't necessary for
lifting; a slightly saw-edged knife works as well or better than the most highly
polished, so I do touch-ups while lifting on the coarse side of a "punjab" razor
hone, equivalent to maybe a soft arkansas or an 800-grit (or coarser) water
stone.

_________________________________________________
*Lifting: in conventional reattachment of boards, the covering cloth or leather
is raised from the board along the spine edge, then the new leather is slipped
in under the flap that has been created. The same is done on the inside, for the
endpapers. There are several techniques for partly detaching the covering,
depending on the leather or paper, the board, and on how good the attachment is.
On most books at least one side of the board will have to be lifted with the
knife, which is similar to a paring knife but skewed opposite and with a smaller
skew angle. This is used to cut between the leather and board, or better,
through the board itself leaving a paper-thin layer of board still on the
leather. Any lumpiness in the cut will be seen when the work is done. And
everything you are trying to cut is crumbly.
Want some idea of how hard this is on a knife's edge, and how hard period? Take
a short 1-1/4" chisel and try to bevel the edge of a piece of eight-inch thick
cardboard with it, making the bevel an inch wide and running down to a feather
edge. Do it without going over any spot twice. And consider that to lift the
leather on an ordinary-sized book, you will need to make an even surface three
inches (not one inch) wide and nine inches long. I couldn't find any videos of
doing it; my guess is that it is too hard for the sort of binder who makes
videos, and they don't want to show the botch-up they make of it. But maybe I'm
just a cynic.
And don't even get me started on lifting an old spine that is adhered directly
to the book. I did find at least one video of this, but it was being botched, so
I averted my eyes.
Tom Conroy.
(Just let me ramble on a few more hours, eventually I will go to sleep and you
can escape)

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