|
KNIFE SAFETY ! Knives
are DANGEROUS!!!
They are heavy and very sharp, even after
use. Keep the
edge away from your body and keep the area clear of others
when handling knives.
Never touch the cutting edge!
To prevent personal injury and damage to the knife, always keep
knives in their holders with screws tightened.
You are aware of the dangers, but others may not be.
Never attempt to hone, polish, or service the knife in any way.
Failure to follow safety procedures may result in severe
lacerations or dismemberment.
Knife Blade Life
Knife blade life, or the time between
sharpenings, can be affected by many factors.
One important factor is the type of paper being cut.
Abrasive paper, such as recycled paper, soft paper such as
newsprint paper, and bound books can all significantly shorten knife
blade life. Also, if the
knife depth is set too deep, the knife will cut too deep into the
cutting stick and can dull the knife blade.
A knife can last anywhere between
2,000 and 5,000 cuts before it needs to be sharpened.
Cutting soft paper (such as newsprint paper) or paper with high
post-consumer recycled content can cause the knife to need sharpening
after only 2,000 to 3,000 cuts.
Cutting pure paper, such as bond paper with no recycled content, or hard
paper can allow the knife to be used for as many as 5,000 cuts before it
needs to be sharpened. In
all cases, the operator should continually check the quality of the cut
to determine when the knife blade needs to be sharpened.
Some characteristics that indicate a blade needs sharpening are:
-
The knife hesitates or stalls
while making a cut.
-
The sheets are not all cut to the
same length (usually the top few sheets are longer than the rest of
the sheets - this is sometimes called “draw”).
-
Cut marks appear on the cut face
of the paper.
-
The profile of the cut (side view)
is not perpendicular to the table.
-
The cut does not appear straight
when viewed from the top.
-
The knife makes a “rougher” sound
as it passes through paper.
-
Nicks are visible on the cutting
edge of the knife.
Cutting Stick
A worn cutting stick can affect the
cut quality of the bottom sheets.
When this happens, the cut stick can be rotated.
Usually, the stick should be rotated one or two times between knife
sharpenings.
There are 8 possible cut stick
positions. The stick can be
rotated 4 times, and then turned end to end, and rotated 4 times again.
Bevel Angle
Challenge recommends that bevel angles
for knives be in the range of 21° to 23°.
In general, a 21° bevel angle will provide better cut quality when
cutting soft paper (such as newsprint), recycled paper, or bound books.
However, 21° angle knives can become dull sooner than 23° knives,
which results in shorter knife blade life.
A knife with a 23° bevel angle, on the other hand, will not dull as
easily, and can provide satisfactory results when cutting most types of
paper.
Helpful Suggestions
It may be beneficial to purchase more
than one set of knives: one set beveled at 21° and the other at 23°.
Note: A set consists
of 3 knives: one in the
machine, one as a back up, and one at the grinder.
If the machine seems to strain but the
cut quality is still good, reduce the pile height.
You may also carefully apply glycerin to the bevel when cutting
hard, coated paper. Tie a
cloth to the end of a stick; dip the stick in glycerin, and apply.
Never apply by hand!
In lieu of glycerin you may lightly rub white bar soap along the bevel.
Lubrication will prolong the life of your machine and reduce
maintenance.
Knife Care
To prevent corrosion, knives are
coated with light oil. It
should be REMOVED WITH CARE.
While removing or installing a knife,
be careful not to allow the edge to bump against the machine.
Nicks will result.
If a knife bolt is damaged, replace
it.
Always keep knife bolts securely
tightened.
Always use the heavy-duty knife bolt
washers provided by Challenge.
Failure to do so could result in scratching or marring of the clamp
face.
Store knives in a dry environment to
prevent corrosion.
Never attempt to service a knife in
any way. |
