5.13.
GLASS KNIFE MANUFACTURE
157
result from breaks which intersect very close to a corner so that a diagonal
score should be very nearly aimed toward this.
The novice handling glass may experience difficulties for a number of
trivial reasons. Difficulties in scoring may result from not holding the
glazier's scoring tool so that the wheel is vertical to the glass. Also it
should be realized that these wheels do get dull in time and cease to
function properly. A good wheel should require very little vertical pressure to make a deep score line. When a fairly rapid score is made with
a good wheel, there will be a slight "sizzling" or "hissing" sound. If inexperienced people mishandle a glazier's tool, and bear down too heavily
upon it, they are apt to flatten spots in its edge which then will not score
properly, and thus it may become impossible to achieve a fully continuous score line.
Another group of problems relate to maintaining the pliers in proper
order. The fulcrum and the pressure points must be of an appropriate
thickness. If strips of tape are used to create these points, they can be
expected to flatten after a few uses, and they must be renewed periodically. Almost every time a piece of glass is broken it can be expected that
some glass chips will be left more or less embedded in the tape, and
these must be carefully rubbed away. We have had the lips of pliers become slightly bent so that they were no longer truly parallel with each
other, and thus did not make proper contact with the glass. Regrinding
then was necessary to re-establish proper linear contact with the glass.
Experiments utilizing more refined glass breaking equipment than handsqueezed pliers (see below) have indicated that the height adjustment
of the fulcrum and the pressure points is quite critical, and must be
varied for different types of glass, as well as when different glass thicknesses are used. Thus it is that the beginner would do well to limit himself to a particular sort of glass until he has gained experience.
the front face of the knife so that the last | to \ inch will be a "free break." When more
simply shaped triangular knives are required, squares of glass are bisected diagonally.
(b) The modified glazier's pliers are positioned so that the fulcrum lies just below
the score line, and the jaws are in the middle of the score line, in the center of the
glass.
(c) Gently increasing pressure breaks the glass as slowly as possible, with the "free
break" deflecting to whichever side of the corner the original score line pointed to.
(d) The completed knife, which can be expected to have a more acute angle, and to
improve, the closer to the corner of the glass rectangle the "free break" terminates.
GLASS KNIFE MANUFACTURE
157
result from breaks which intersect very close to a corner so that a diagonal
score should be very nearly aimed toward this.
The novice handling glass may experience difficulties for a number of
trivial reasons. Difficulties in scoring may result from not holding the
glazier's scoring tool so that the wheel is vertical to the glass. Also it
should be realized that these wheels do get dull in time and cease to
function properly. A good wheel should require very little vertical pressure to make a deep score line. When a fairly rapid score is made with
a good wheel, there will be a slight "sizzling" or "hissing" sound. If inexperienced people mishandle a glazier's tool, and bear down too heavily
upon it, they are apt to flatten spots in its edge which then will not score
properly, and thus it may become impossible to achieve a fully continuous score line.
Another group of problems relate to maintaining the pliers in proper
order. The fulcrum and the pressure points must be of an appropriate
thickness. If strips of tape are used to create these points, they can be
expected to flatten after a few uses, and they must be renewed periodically. Almost every time a piece of glass is broken it can be expected that
some glass chips will be left more or less embedded in the tape, and
these must be carefully rubbed away. We have had the lips of pliers become slightly bent so that they were no longer truly parallel with each
other, and thus did not make proper contact with the glass. Regrinding
then was necessary to re-establish proper linear contact with the glass.
Experiments utilizing more refined glass breaking equipment than handsqueezed pliers (see below) have indicated that the height adjustment
of the fulcrum and the pressure points is quite critical, and must be
varied for different types of glass, as well as when different glass thicknesses are used. Thus it is that the beginner would do well to limit himself to a particular sort of glass until he has gained experience.
the front face of the knife so that the last | to \ inch will be a "free break." When more
simply shaped triangular knives are required, squares of glass are bisected diagonally.
(b) The modified glazier's pliers are positioned so that the fulcrum lies just below
the score line, and the jaws are in the middle of the score line, in the center of the
glass.
(c) Gently increasing pressure breaks the glass as slowly as possible, with the "free
break" deflecting to whichever side of the corner the original score line pointed to.
(d) The completed knife, which can be expected to have a more acute angle, and to
improve, the closer to the corner of the glass rectangle the "free break" terminates.