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Re: [BKARTS] Restoring Second-hand Board Shears



>I have known board shears to be damaged when a user who
>didn't know enough to keep the blades pulled together
>readjusted the blade setting into tight contact all along,

If the contact is adjusted too tight, the blades can cut each other. Also
if they are not set precisely parallel. Pulling the blade when cutting can
also damage the blades. Proper blade alignment is critical to good cutting.
Bill Minter's board shears video is well worth the price!

When teaching board shear adjustment and use I make a point of telling the
students NOT to pull the blade when making a cut on paper, and only to
exert enough pressure when cutting board to keep the blade from splaying
outward. In my shop the blade is adjusted so it makes a light whooshing
sound as it closes, and cuts a piece of tissue paper the length of the
blade without any pressure on the blade at all. If the blades are not
making proper contact their entire length, I shim the curved blade with
paper or playing cards.

When cutting paper or card stock on a Jacques shears I do not even hold the
blade. I just give it a gentle push downwards and let the weight of the
blade do the cutting. I have seen blades ruined by people pulling the
curved blade against the fixed blade, with the result that the blades cut
each other, causing an undesirable bevel on the flat side of the blade.
That, of course, causes people to pull even harder to make it cut.  Then it
has to be removed from the cutting table and sent out to be reground. Some
commecial operators in the grinding business  reinstall the blades so they
will not cut without pulling. That makes them get a bevel on the flat side
again. So then they grind down the flat side of the blade again. Soon they
have to replace the blade, and that ain't cheap! I suggest to everyone to
do your own blade alignment.

I have never had to replace a blade on any of my shears and I do not remove
the blade for sharpening. If the blade were to get a nick in it because
someone left a ruler in the wrong place on the cutting table, I can
understand the necessity of grinding it down.  But for regular maintenance
I simply use an oilstone on the curved blade bevel while it is in place.
Then I gently stone the flat side just to remove the burr, if one forms.
The fixed blade rarely needs any sharpening, but a light touch with the
stone on the top (horizontal) surface (and burr removal on the vertical) is
useful now and then. Taking too much off the vertical face of the fixed
blade (as is done by commercial grinders) necessitates redrilling to recess
the screw heads and premature blade replacement. If the horizontal plane of
the fixed blade gets worn down it's easy enough raise it with the adjusting
screws. After sharpening I wipe the blade with alcohol to remove any
residue from the oilstone.

What I have observed to be the most critical issue, on a properly adjusted
shears, is the posture of the operator. I recommend balancing the body
vertically on one leg, with just enough pressure exerted on the foot clamp
with the other leg to keep the paper from slipping. If the motion of the
arm is not influenced by the body leaning toward or away from the blade,
one can sweep down in line with the cut, without pushing the blade away or
pulling it in harder than necessary for the thickness of the material being
cut.

When students get rough edges on their boards while cutting, it wastes a
lot of time sanding to get a usable board, and may require a recut if too
much material is removed or the sanding causes the squareness of the board
to be lost. Correcting their posture generally results in crisp board edges
the correct size with a single cut..

--
 Richard
 http://minsky.com
 http://www.centerforbookarts.org

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