Oilless fluid for scoring glass

A cutting fluid is disclosed comprising one or more halogenated hydrocarbons dissolved in one or more paraffin, naphtha, or aromatic solvents. Use of the cutting fluid produces a glass edge with increased edge strength compared with a cut edge produced by dry scoring. The cutting fluid is completely evaporative, leaving no residue, thus eliminating the need for washing. Further, use of the cutting fluid extends the useful life of the cutting tool. Blends are formulated to meet specific evaporation rates required by variations in wareroom equipment and practices.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to the art of cutting glass and 
particularly to the art of scoring glass in the presence of a fluid. 
2. Description of the Prior Art 
The cutting of individual glass articles from a large glass sheet or ribbon 
is generally accomplished by moving a glass-cutting tool across the 
surface of the glass with sufficient force to effect a score in the 
surface of the glass. This may be done with no fluid (dry scoring) or in 
the presence of a fluid. Cutting fluids may be used for the purpose of 
lubricating the cutting wheel and axle and the glass, but are now 
generally used primarily to prevent or retard healing of the score. It is 
known that healing is retarded by excluding atmospheric moisture from a 
score. Therefore, cutting fluids are typically in the form of oils or oils 
mixed with solvents. 
U.S. Pat. Nos. 3,894,456 and 3,914,180 to Boller et al. disclose a cutting 
fluid which comprises methyl chloroform and a non-volatile hydrocarbon 
oil. The methyl chloroform acts as a cutting tool lubricant, then, being 
highly volatile, evaporates. The hydrocarbon oil, being non-volatile, 
forms a residue which binds wing chips along the edge of the score thus 
preventing spalling. An emulsifying agent may be added to the cutting 
fluid to aid washability for removal of the non-volatile oil from the 
glass surface. 
Belgian Pat No. 819,914 to Simpkin et al. discloses a cutting fluid 
comprising a hydrophobic cutting oil and a hydrophobic organic solvent. 
The oil is thought to reduce lateral cracks produced along the score by 
water vapor in the atmosphere and consequently to reduce the force 
required subsequently to snap the glass score while the solvent acts as a 
thinner and is removed by evaporation. 
SUMMARY OF THE INVENTION 
The present invention relates to an improved glass cutting fluid which 
contains no oil and leaves no residue on the glass surface, thereby 
eliminating the need for washing. More particularly, this invention 
relates to a method of cutting glass employing an oilless cutting fluid 
which produces a spall-free cut glass edge having increased edge strength 
over an edge cut by dry scoring and which also extends the useful life of 
the cutting tool. 
The primary component of the improved glass cutting fluid of the present 
invention is a halogenated hydrocarbon. The cutting fluid of the present 
invention may consist essentially of a liquid halogenated hydrocarbon or 
may comprise a halogenated hydrocarbon and a paraffin, naphtha or aromatic 
solvent. The cutting fluid need not contain an emulsifying agent to render 
the fluid water-washable since the cutting fluid is essentially completely 
removed by evaporation. Solutions or blends are adjusted for evaporation 
rates to meet the specific conditions imposed by production procedures and 
both automatic and manual operation equipment. 
The method of cutting glass of the present invention involves effecting a 
score on the surface of the glass in the presence of the cutting fluid of 
the present invention and propagating the score to produce a cut through 
the glass. The cut edge of glass scored by the method of the present 
invention has increased edge strength compared with a cut edge of glass 
scored in the absence of the cutting fluid of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A cutting fluid is applied at the interface of a scoring tool edge and a 
major surface of a sheet of glass, supported on a substantially flat 
surface, along the intended scoring path. The cutting fluid comprises a 
halogenated hydrocarbon, preferably a chlorinated hydrocarbon such as 
1,1,1-trichloroethane or perchloroethylene. The halogenated hydrocarbon is 
preferably used in combination with a paraffin, naphtha or aromatic 
solvent in order to permit adjustment of evaporation rate, fire 
resistence, cost and the like to satisfy specific needs of a cutting 
operation. A naphtha solvent is preferred for cutting flat glass in a 
primary glass manufacturing factory in which high speed, automatic cutting 
is accomplished. 
The cutting fluid preferably comprises from 2 to 98 percent by volume 
halogenated hydrocarbon and from 98 to 2 percent by volume solvent. 
Selection of cutting fluid components and proportions will vary with such 
factors as cutting process, design of cutting and wareroom systems and 
materials, and desired score quality and edge strength. 
The cutting fluid may be applied as a liquid or mist according to any of 
the techniques known in the glass cutting art. Preferably, the cutting 
fluid is applied continuously, such as by flowing down the cutting tool 
and transferring to the glass surface being scored. 
The cutting tool is preferably a cutting wheel made from steel or tungsten 
carbide or other material having suitable properties. The cutting wheel 
has a glass contact edge with a cutting angle preferably between about 
115.degree. and 155.degree.. The cutting wheel is moved across the surface 
of the glass along the intended scoring path with sufficient force to 
effect a score, i.e., to produce a major vent in the glass essentially 
perpendicular to the glass surface. 
The range of force sufficient to effect a score which can be consistently 
opened without causing lateral vents to erupt with the glass surface 
adjacent the score (spalling) is the working range of wheel load. Use of 
the cutting fluids of the present invention expands the working range by 
allowing the use of higher wheel loads. Since it has been found that wheel 
load must be increased as the wheel wears to obtain acceptable score 
quality, expansion of the working range as in the present invention 
extends the useful life of the cutting wheel. 
After the glass surface is scored, the score is propagated to produce a cut 
through the glass such as by applying a bending moment about the score 
causing the glass to fracture with a resultant smooth, straight, strong, 
spall-free edge perpendicular to the major surfaces of the glass. 
Preferably the scored glass is opened either manually using glass 
cut-running pliers commonly employed in the art or is opened mechanically 
by snapping. 
Since the cutting fluid of the present invention is completely removed by 
evaporation, the cut glass edge is free of any residue and does not 
require washing. The cut glass edge exhibits greater edge strength than 
the cut edge of glass scored without the cutting fluid of the present 
invention. 
The invention may be further illustrated by the specific examples which 
follow. 
EXAMPLE I 
A cutting fluid is prepared having a composition of 75 percent by volume 
1,1,1-trichloroethane and 25 percent by volume of a naphtha solvent 
available from Ashland Chemical Co. under the designation Rule 66 Mineral 
Spirits (7 percent aromatics). Test strips of 7/32 inch (6 millimeter) 
thick soda-lime-silica float glass measuring 4 by 26 inches (about 100 by 
800 millimeters) are cleaned with a solution of a commercial glass 
cleaner. A test strip is placed atop a wooden sled which travels along the 
base of a scoring apparatus beneath a cutting head positioned midway down 
the length of the base. A six pound load is applied to the horizontal pan 
affixed to the top of the cutting head which is equipped with a 7/32 inch 
(6 millimeter) diameter tungsten carbide cutting wheel having a 180 grit 
surface finish (regular grind) and a 145.degree. cutting angle. A film of 
cutting fluid approximately twice the width of the cutting wheel is 
applied at the midpoint of the width of the glass strip along its entire 
length. The sled bearing the glass test strip is then driven at a rate of 
1 foot per second beneath the cutting wheel to effect a score on the glass 
surface along the path of the cutting fluid. The same procedure is carried 
out with additional test strips. After the scores are opened, using 
conventional glass score opening apparatus, the edge strengths of the cut 
edges are measured by beam load testing. The samples, which bear no 
residue since the cutting fluid is completely evaporative, are placed on a 
Baldwin Tester loading at a rate of 1000 pounds per square inch per minute 
until glass failure. The samples exhibit an average edge strength of 
13,218 pounds per square inch, an increase of 43 percent over the edge 
strength of 9270 pounds per square inch measured for the cut edges of 
glass scored with no cutting fluid. 
EXAMPLE II 
A large sheet of 7/32 inch (6 millimeter) float glass is cleaned as in 
Example I. A cutting fluid essentially of dichlorobenzene of which about 
80 percent is orthodichlorobenzene is applied to the surface defining a 
rectangular scoring pattern measuring 36 by 48 inches. The glass is cut by 
picture-frame scoring and opening using the same type cutting wheel and 
load (145.degree. and 6 pounds) as in Example I. Edge strength of the cut 
edge is measured by thermal loading to permit effective measurement of 120 
inches of cut edge as opposed to 10 inches by beam loading. Thermal 
loading is accomplished by placing on the sample a 341/2 inch by 461/2 
inch heating blanket and electrically heating until glass failure. The 
stress at breakage is estimated from the mirror radius at the origin. The 
edge strength of the sample scored with dichlorobenzene is 9000 pounds per 
square inch compared with 6770 pounds per square inch for the cut edge of 
glass scored with no cutting fluid. 
EXAMPLE III 
Test glass strips are cleaned, scored and opened as in Example I except 
that the cutting fluid comprises 75 percent by volume 
1,1,1-trichloroethane and 25 percent by volume of a paraffin solvent 
available from Sun Oil Company under the designation Sun T Mineral Spirits 
(aliphatic hydrocarbon). The edge strengths of the cut edges are measured 
by beam load testing as in Example I and average 12,350 pounds per square 
inch, an increase of 27 percent over the edge strength of 9700 pounds per 
square inch for the cut edges of glass scored with no fluid. 
EXAMPLE IV 
To determine the effect of cutting fluids of the present invention on the 
working ranges of cutting wheels, scores are made through a fluid 
comprising 75 percent by volume 1,1,1-trichloroethane and 25 percent by 
volume naphtha as in Example I but under wheel loads varying from 3 to 26 
pounds using cutting wheels having 134.degree., 145.degree. and 
150.degree. cutting angles. Using a 7/32 inch (6 millimeter) tungsten 
carbide cutting wheel with a 134.degree. cutting angle, acceptable scores 
are made under wheel loads ranging from 4 to 14 pounds compared with a 
working range of 4 to 10 pounds when no fluid is employed. Using the 
145.degree. cutting wheel, the working range with the cutting fluid of the 
present invention is from 5 to 16 pounds compared with a working range of 
from 5 to 12 pounds with no fluid. The working range for the 150.degree. 
cutting wheel is from 8 to 16 pounds when no fluid is used and is extended 
to a range of from 7 to 20 pounds when the cutting fluid of the present 
invention is employed. 
The test strips scored at wheel loads within the working ranges of the 
cutting wheels are opened and the edge strengths of the cut edges measured 
as in Example I. FIG. 3 is a comparison of the cut edge strength versus 
wheel load between dry scoring and scoring with the cutting fluid of this 
example. 
Cutting fluids and a method for performing a glass cutting operation using 
such fluids have been disclosed herein. Numerous variations and 
modifications of the cutting fluid compositions and method will become 
obvious to those skilled in the art. Such variations and modifications 
fall within the spirit and scope of the present invention and are intended 
to be within the scope of the appended claims.