A process for machining glass by placing a rotating carbide working surface under minimum pressure against an area of glass to be worked is described. Concurrently the region between the working surface and the area of glass is wet with a lubricant consisting essentially of a petroleum carrier, a complex mixture of esters and a complex mixture of naturally occurring aromatic oils

Rice, S. H.

English

NASA Technical Reports Server

[111 4,303,705 
Rice [45] May 17, 1983 
[54] 
[75] Inventor: Stephen H. Rice, Waldorf, Md. 
[73] Assignee: The United States of America as 
METHOD FOR MILLING AND DRILLING 
GLASS 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 173,520 
[22] Filed: Jul. 30, 1980 
[51] Int. Cl.3 ......................... B23B 35/00; B23C 3/00 
[52] U.S. C1. ...................................... 409/131; 125/20; 
408/1 R;408/61 
[58] Field of Search ....................... 409/131, 132, 135; 
29/557, 558; 408/1, 59, 144, 60, 61; 125/20, 38 
1561 References Cited 
U.S. PATENT DOCUMENTS 
2,010,257 8/1935 Fehse .................................. 408/1 X 
2,478,846 8/1949 Smith .................................... 48/59  
FOREIGN PATENT DOCUMENTS 
49-36375 9/1914 Japan ...................................... 408/1 
OTHER PUBLICATIONS 
“Tap Magic Cutting Fluids”, The Steco Corporation, 
2330 Cantrell Rd., Little Rock Ark. 
Primary Examiner-Z. R. Bilinsky 
Attorney, Agent, or Firm-John 0. Tresansky; John R. 
Manning; Robert E. Bushnell 
1571 ABSTRACT 
A process for machining glass by placing a rotating 
carbide working surface under minimum pressure 
against an area of glass to be worked and concurrently 
wetting the region between the working surface and the 
area of glass with a lubricant cohsisting essentially of a 
petroleum carrier, a complex mixture of esters and a 
complex mixture of naturally ocCurring aromatic oils. 
7 Claims, 1 Drawing Figure 
FIRST POINT 
ANGLE 12 \ 
BIT 
https://ntrs.nasa.gov/search.jsp?R=19830018787 2020-03-22T00:43:50+00:00Z
U.S. Patent May 17, 1983 
FIRST POINT 
SHANK 27 
4,383,985 
BIT 
4,383,785 
2 1 
processes unsuitable for performing fine machining 
details. 
STATEMENT OF INVENTION 
METHOD FOR MILLING AND DRILLING GLASS 
ORIGIN OF THE INVENTION 
5 Accordingly, it is an object of the invention to pro- The invention described herein was made by an em- 
manufactured and used by or for the Government for 
governmental purposes without the payment of any 
royalties thereon or therefor. 
DESCRIPTION 
vide an improved process for machining glass. 
glass to close tolerances. 
10 and cheaply machining glass. 
ployee Of the United States Government and may be Another object is to provide a process for machining 
A further object is to provide a process for reliably 
It is still another object to provide a process for ma- 
chining glass to smaller dimensions than possible with 
prior art processes. 1. Technical Field The invention to the machining Of glass and, It is still another object to provide a quick process for 
more particularly, to a process for milling and drilling 15 machining glass. 
glass. 
great enough to enable it to be put to certain useful 
purposes. Its rigidity, or hardness, however, has limited Yet another object is to provide a process that re- 
the suitability of glass for machining, thereby restricted 2o duces the extent of chipping along the edges and rims of 
its usefulness. Additionally, when machined, its hard- machined of glass. 
ness causes chipping and cracking in regions adjoining A further object is to provide a process for making 
the area worked. This characteristic eliminates the pos- machined regions with smooth wall surfaces in glass. 
sibility of machining glass with any degree of precision Briefly, the foregoing and other objects are achieved 
except ~ with diamond grinding wheels. 25 by a machining process wherein the area of the glass to 
be worked is subiected to a rotating carbide workpiece 
It is yet another object to provide a process that 
has been defined as a liquid whose rigidity is reduces the occurrence of fracture during machining of 
glass. 
2. Background Art 
Currently, there are several methods in use for per- 
forming such machining operations on glass as drilling 
glass sheet stock. The quickest, although perhaps, least 
accurate, involves little more than directing a low speed 
projectile, such as a BB size shot discharged from an air 
gun against the area of glass to be drilled. When viewed 
from the side of impact, typically the projectile makes a 
circular hole with a moderately chipped rim. The ob- 
verse or exit side, however, is invariably marred by a 
rough conic crater having a base diameter several times 
the diameter of the circular hole. Cracking of a large 
adjoining area is quite common. 
A more accurate method commonly practiced by 
glaziers uses a case hardened ceramic drill bit driven 
either by a brace or by a slowly turned hand-powered 
drill. Very little pressure is applied to the drill bit. The 
working surface of the drill bit is kept wet with a light 
lubricating oil or, perhaps, turpentine. Once the very tip 
of the drill bit pierces the glass sheet, the drill is re- 
moved and reapplied, again with very little pressure, to 
the obverse side of the glass sheet and the hole is com- 
pleted. The inaccuracy or wobble of a hand-powered 
drill bit limits the possibility of precision and restricts 
this method to holes larger than one-eight of an inch in 
diameter. 
A more precise and expensive method, practiced 
mainly in optical instrument shops, uses a hollow core, 
diamond faced drill bit. While being applied against 
glass stock, water is forced through the hollow core to 
cool the region worked and to flush loose glass particles 
from the hole. However, diamond tool bits have a ten- 
dency to mar the walls of a hole with cut patterns and 
extensively chip the entrance and exit rims. Addition- 
placed with a minimum pressure against the area of the 
glass to be worked and which is being wetted by a 
lubricant consisting essentially of a petroleum carrier, a 
30 complex mixture of esters and a complex mixture of 
naturally occurring, purified aromatic oils. 
BRIEF DESCRIFTION OF THE DRAWING 
The invention will be more readily appreciated when 
35 considered in conjunction with the accompanying soli- 
tary FIGURE wherein a front view of a carbide drill bit 
40 
45 
50 
55 
ally, the risk of fracture is fairly high. The necessity of 60 
a hollow core mandates a lower limit upon the bit diam- 
eter of about 0.125 inches. 
A lack of precision due to extensive chipping occur- 
ring along rims and or machined surfaces is one of the 
chief disadvantages of these prior art methods. Their 65 
unreliability caused by the high risk of fracture during 
machining, is another disadvantage. Furthermore, the 
relatively large dimensions of the tools used make these 
is shown. 
DETAILED DESCRIPTION OF THE 
INVENTION 
In accordance with the invention, a glass workpiece 
is mounted on a soft wax layer for uniform support and 
the wax is allowed to cool before machining begins. A 
tool with a hard working surface such as tantalum car- 
bide or tungsten carbide, preferably one made of solid 
carbide, is mounted in a small Jacobs type chuck of a 
precision type bench drill press or a horizontal milling 
machine. The working surface of the tool and the sur- 
face of the glass to be worked are wetted with a lubri- 
cant made of a complex mixture of synthetic esters, a 
complex mixture of aromatic oils of plant origin ar- 
ranged with a definite distribution, and a middle molec- 
ular weight petroleum distillate carrier. The tool is 
driven in high speed rotation, preferable at 1,800 or 
greater revolution per minute, and gently placed against 
the surface of the glass. While in contact with the glass, 
the region between the working surface of the tool and 
the region of the glass worked is kept wet with the 
lubricant. Little or no pressure is applied to the tool 
during machining. With the exception of heat generated 
by the frictional forces of machining, the process is 
conducted while the glass workpiece is at room temper- 
ature. If a deep hole is to be drilled, it is well to periodi- 
cally raise the tool bit in order to clear the hole of glass 
dust and particles although blind holes of less than one 
inch in depth and one-sixteenth inch diameter have been 
drilled in a single pass. Similarly, if a deep groove is to 
be milled, it is desirable to make a series of step passes, 
4,383,785 
3 4 
each 0.005 to 0.010 inches in depth. Generally, it is The detailed description refers to glass generally. The 
preferable to drill a pilot hole before such operations as process disclosed is known to work with plate glass, 
machining a central groove in one face of a glass work- window glass, Pyrex glass, crown glass, Cervit glass, 
piece. and Zerodur glass. 
One type of solid carbide drill bit 10 used with partic- 5 The foregoing detailed discussion describes a room 
ular success in this process is a “Spacedrill” circuit temperatme process for machining glass to precision 
board drill, size 50, SHCB, manufactured by Space tolerances. The tools used are commercially available 
Implements Company of Burbank, Calif. This Particular and have a hardness greater than that of the glass ma- 
tool is a double fluted drill 6-G a body 20 wth two chined, but not as great as the diamond faced tools 
flutes 16) ground with two adjoining Point angles 12914 10 previously used. At least one formulation of the lubri- 
at the end opposite the drill h n k  27- This type of drill cant is also commercially available. Generally, it is best 
bit is shown in the drawing. End mills and d l  of the to keep the region between the working surface of the 
other tools used in machining the glass examplars were tool and the worked surface of the glass wet with the 
also commercially available items obtained from a shop lubricant during a machining operation by periodically 
tool crib. l5 squirting a small quantity of lubricant at the region to 
The lubricant described in COnJUnCtiOn with the de- 
description is Znanufactured and commercially 
distributed by Steco Corporation, 3400 Asher Avenue, 
replenish lubricant displaced by the region by the tool 
and absorbed by glass dust. In lieu of intermittent appli- 
cation of the lubricant, a continuous stream of lubricant 
Little Rock, Ark., under the name of ‘TAP MAGIC 
for aluminum.” 
The general nature of the invention having been set 
forth, the following illustrative examples are presented 
as typical embodiments thereof. It will be understood 
that the invention is not limited to these examples, but is 
susceptible to various modifications that will be recog- 25 
nized by one of ordinary skill in the arts. The dimen- 
sions stated were, where indicated, taken from the tool 
dimension or obtained by use of shop gauges. 
EXAMPLE 1 
may be directed at the region worked. compa~son 
2o with the dimensions of machined regions, the extent of 
chipping along edges and rims is invariably negligible. 
this process allows machining of adjacent 
regions separated by as little as o.oo2 inches of wall 
thickness. Typical applications for this process include 
drilling mounting bolt holes in curved Cervit mirror 
blanks, drilling feed-through sensor instrument holes in 
fiber optic bundles, and milling precision grooves in 
blocks of crown glass. 
What is claimed and desired to be secured by issue of 
A glass m~croscope slide about one sixteenth of an 30 a Letters Patent of the United states, is: 
inch thick was coated with a warm layer of red wax and ’. A process for machining glass, comprising the steps 
a second, identical microscope slide was placed on top 
move air bubbles from the wax layer between them. 35 
When cooled to temperature, a few drops ofTAP 
MAGIC for aluminum were squirted onto the exposed 
surface of the top slide. A series of six adjacent 0.018 
diameter holes were drilled along a straight line, 
through both slides. The tool used was a Spacedrill 40 
point angles. For the first adjacent two holes, wall 
thickness was about 0.009 of an inch; wall thickness 
between the penultimate and last holes was about 0.002 
of an inch. Both slides were free of fractures. Entry and 45 Of: 
exit rims of all twelve holes exhibited very little or no 
chipping. Visual inspection showed the walls of the 
holes to be of uniform smoothness. 
EXAMPLE 2 
A near cube of crown glass about two inches to a side 
was mounted in the manner described in Example 1, on 
a warm layer of blanchard wax. When cooled, a one 
half inch wide groove was milled across two-thirds of 
one face of the cube with a double fluted, solid carbide 55 
end mill rotating at about 1800 revolutions per minute. 
The end mill was periodically wetted with a squirt of 
TAP MAGIC @ for aluminum during milling. Succes- 
sive passes increased the depth of the groove to seven 
thirty-seconds of an inch. Visual inspection revealed the 60 hundreds of motions per minute, 
rim between the face and walls of the groove to be 
uniformly finely chipped to the extent of creating an 
extremely fine level along the rim. The walls were uni- 
formly smooth. The base or floor of the groove con- 
tained periodic occlusions. The rim, walls and floor of 65 
the groove felt smooth to a firm touch of the fmger. A 
jobe block 0.001 of an inch thicker than the diameter of 
the end mill could not be inserted into the groove. 
Of: 
of the wax layer. The two slides were pressed to re- placing a carbide working surface of a solid too1 
against an area OF a glass workpiece; 
wetting the working surface with a lubricant consist- 
ing essentially of a middle molecular weight petro- 
leum distillate carrier, a complex mixture of esters, 
and a complex mixture of naturally occurring aro- 
matic Oils; and 
motion and minimal pressure against said glass 
workpiece area. 
2. A Process for machining glassy comprising the steps 
Placing a rotating carbide Working surface subject to 
minimum pressure against an area of glass to be 
worked; 
wetting the region between the working surface and 
the area to be worked with a lubricant consisting 
essentially of a mixture of a middle molecular 
weight petroleum distillate, a complex mixture of 
synthetic esters, and a complex mixture of natural 
occurring, purified aromatic oils. 
3. The Process set forth in Claims 1 or 2, wherein said 
carbide working surface is a double fluted drill ground 
with a plurality of adjoining point angles. 
4. The process set forth in claims 1 or 2 wherein said 
working surface is driven at a speed on the order of 
5. The process set forth in claim 3 wherein the drill 
6. A process for machining glass, comprising the steps 
driving a tool having a working surface of a material 
exhibiting a hardness greater than glass with con- 
tinuous motion and minimal pressure against a glass 
workpiece; and 
double fluted, circuit board drill with two adjoining driving said wetted Working Surface With COntinUOUS 
50 
has a diameter between 0.125 and 0.018 inches. 
of: 
4,3 83,785 
5 6 
wetting the region between said working surface and 
said glass workpiece with a liquid phase lubricant 
consisting essentially of a complex mixture of syn- 
thetic esters, a complex mixture of purified are- 
matic oils of plant origin arranged with a definite 
distribution, and a middle molecular weight petro- 
leum distillate carrier. 
7. The process of claim 6 wherein said tool is solid. 
5 * * * * *  
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Method for milling and drilling glass

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