xt7wdb7vpn3z https://exploreuk.uky.edu/dips/xt7wdb7vpn3z/data/mets.xml  Nighman, C. E. 1940 Other contributors: Kiessling, O. E. (Oscar Edward), 1901- ; National Research Project on Reemployment Opportunities and Recent Changes in Industrial Techniques (U.S.); United States. Bureau of Mines. xiii, 158 p. : ill. ; 26 cm. Mineral technology and output per man studies ; report no. E-11. UK holds archival copy for ASERL Collaborative Federal Depository Program libraries. Call number FW 4.7:E-11. books  English Philadelphia, Pa. : Work Projects Administration, National Research Project in cooperation with Dept. of the Interior, Bureau of Mines This digital resource may be freely searched and displayed in accordance with U. S. copyright laws. Maryland Works Progress Administration Publications Rock Drilling by C.E. Nighman and O.E. Kiessling text Rock Drilling by C.E. Nighman and O.E. Kiessling 1940 1940 2015 true xt7wdb7vpn3z section xt7wdb7vpn3z *  . ‘
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FEDERAL WORKS AGENCY lg
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F. C. HARRINGTON CORRINGTON GILL g
Commissioner Assistant Commissioner i
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NATIONAL RESEARCH PROJECT f
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Reemployment Opportunities and Recent Changes hi?
in Industrial Techniques_ L {
DAVID WEINTRAUB ‘  
Director `Kf
In cooperation with cmg
UNITED STATES DEPARTMENT OF THE INTERIOR `§
BUREAU OF MINES .§
JOHN W. FINCH, Director ' zi?
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Mineral Technology and Output. Per Man Studies  
" O. E. Kiessling, Economist in Charge ·` iw N_, , §
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  MODERN JACKHAMMER DRILLS AT A SURFACE OPERATION
  This hand—held machine weighs about 5IO pounds and_is actuated by com-
  pressed air. The hammer strikes the drill steel, which is automatically
  rotatedi about 2,000 blows per minute. The jackhammer is‘used principally
¥ to dril holes in a downward direction.
F
§I The deyelopment of the jackhammer repres_ented one of the greatest
I; advances in drilling technology. I It not only is widely used in mining and A
S. quarrying but is employed extens1vely for many other types of work. with
I this too a man can drill at least 20 times as rapidly as he could by hand.
 
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MINERAL TECHNOLOGY AND OUTPUT PER MAN STUDIES  
R O C K D R I I. L I N G  
5E
by  
C. E. Nighman ·  
and §
O. E. Kiessling  
I E
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WORK PROJECTS ADMINISTRATION, NATIONAL RESEARCH PROJECT `  
In cooperation with  
DEPARTMENT OF THE INTERIOR, BUREAU OF MINES  
Report No. E—11  
lv
Phzladelyihw., Penrzsylv<1n1a .  
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February 1Q4O  
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  ` THE WPA NATIONAL RESEARCH PROJECT `
  _ ` ON REEMPLOYMENT OPPORTUNITIES AND RECENT CHANGES
  . IN INDUSTRIAL TECHNIQUES
15V
  Under the authority grantedby the President in the Execu-
  t1ve Order which created the Works Progress Adm1n1strat1on,
i ’ Administrator Harry L. Hopkins authorized the establishment
§ `Z of a research program for the purpose of collecting and ana-
1; lyzlng data bearlngon problems of employment, unemployment,
; and relief. Accordlngly, the National Research Program was
established In October 1935 under the supervlslon of Corrington
  Gill, Assistant Administrator of the NPA, who appointed the
  directors of the Individual studies or projects.
  The Project on ReempIoymentOpp0rtun1t1es andRecent Changes
, ln Industrial Techniques was organized In December 1935 to
,’j f‘ 1nqu1re,w1th the cooperat1on of Industry, labor, and govern-
fx l mentaland private agencles, lntothe extent of recent changes
» in 1ndustr1al techniques and to evaluate the effects of these
· changes on the volume of employment and unemployment. David
` V. Weintraub and Irving Kaplan, members of the research staff
’.‘’ of the Divlslonof Research, Statlstlcs, and Flnancewere ap-
·   pointed, respectively, Dlrectorand Associate Dlrector of the
  Project. The task set for them was to assemble and organize
F, lf the existing data wh1ch bear on the problem and to augment
  S these data by fleld surveys and analyses.
  To th1s end, many governmental agencies whlchare the col-
`, ¤— lectors and reposltorles of pertlnent Informatlonwere lnvltea
" · to cooperate. The cooperatlng agencies of the Unlted States
j , Government Include the Department of Agriculture, the Bureau
§  of Mlnes of the Department of the Interior, the Bureau of
    Labor Statlstlcs of the Department of Labor, the Rallroad
I T; Retirement Board, the Lioclal Security Board, the Bureau of
{ ` Internal Revenue of the Department of the Treasury, the De-
  partment of Commerce, the Federal Trade Commission, and the
 ` Tariff Commission.
  The followlng private agencles joined wlth the National
I yl Research Project 1n conducting special studies: the Indus-
  = trial Research Department of the University of Pennsylvanla,
§ the National Bureau of Economlc Research, Inc., the Employ-
  ment Stablllzatlon Research Institute of the Unlverslty of
  Minnesota, and the Agricultural Economics Departments In the
5* IY Agrlcultural Experiment Stations of California, Illinois,
  Iowa, and New York.
  Since September 1, 1939, the Project has been sponsored
2, by the National Resources Plannlng Board, Executlve Office
,' of the President, washington, D. C.
; l5r£;$=;;_
35

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1%
FEDERAL WORKS AGENCY  
.\ WORK PROJECTS ADMINISTRATION  
1734 New YORK Avenue Nw. K 3;*
wAsH|NGTON,¤.c. i
F.c.HARR1NGT0N f
comnussmnan or wonx r-noiscrs I ;§
4
February 5, 1940 hg
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Colonel F. C. Harrington g
Commissioner of Work Projects %
S i r :  
, ji
One of the most time-consuming operations in the f
extraction of minerals is that devoted to the drilling Q
of holes preparatory to blasting. A great deal of y
effort has therefore been concentrated on the improve- %
ment of drilling techniques. Since the introduction §
of the first practical mechanical rock drill, about ·§
1865, the progress of drilling technology has been Nt
rapid and has increased labor productivity in all gf
fields of mining. The report herewith transmitted is ‘y%
concerned with the types of advance that have been `I
made in drilling technology, with the rate at which Ԥ
drilling has been mechanized, and with the effects ff
of its mechanization on production, employment, and ·`é
output per man. I.?
Since about 1917, total employment in mining has il?
been decreasing and the increased productivity of 1
labor in drilling has doubtless contributed to this ag
decline. For example, the rate of drilling under- E
ground with hand methods was about 4 feet per driller- ,;
shift. About 1910 the piston drill was putting down 1.
holes at the rate of roughly 2O feet per man-shift. ji
The hammer drill which replaced the piston drill ac- L
complished at least 80 feet per man-shift. E
Changes in drilling methods have also reduced the E
proportion of the mine labor force engaged in drill- §
ling and brought about changes in the nature of the Q
drilling job itself and in the aptitudes and skills E
required of the driller. Strength and endurance are i
no longer so important as quick reaction time and E
training in the use of mechanical devices. Individual i
experience and skill are not so necessary as they once Q
were. To an increasing extent the drill operator g
2
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    _· ' . · V . ‘ r ., ’ r nn _— ' y .; Q.
é., drills in accordance with specifications prepared by
y A mine technicians.
l§_ It may be assumed that the demand for minerals
{ f will maintain a moderate increase with the growth
’} _ of population and the continued expansion of industry.
§· The outlook for the near future, however, indicates a
yl minor reduction in the labor force employed in mineral
§· drilling unless the production increase is greater
ji. than anticipated. That is, it is likely that the
ti tendency of greater production to increase employment
gh will be more than offset by technical advances con~
Q tinuing along lines followed in the recent past.
é Over a longer period forces of depletion will
éy necessitate the working of lower—grade deposits and
{_. the drilling and breaking of much greater tonnages of
j· ore and rock in order to obtain a given amount of
;* commercially useful product. In spite of the expected
gw continuance of advance in drilling techniques, and
k‘· assuming that the United States will continue to pro-
vide its own mineral supplies, it appears that long-
, time forces will make for an increase in the number of
{ _ men employed in drilling at mines.
A @T` Respectfully yours,
Eli 6* ° »f   ·
gy Carrington Gill
{ A Assistant Commissioner
 
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CONTENTS ,4*};
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Chapter Page g
Ll
Pammcs ...................... xi  
ACKNOWLEDGMENTS .................. xiii Q
Z  
I. INTRODUCTION ................... 1 i
The stimulus for drill mechanization ...... 1 pg
The function of drilling ............ 3 `lg
Scope of the study ............... 4 §
. [
II. THE TRANSITION FROM HAND TO MECHANIZED DRILLING. . 6 Q
Hand-drilling methods .............. 6 Q
The auger drill ................ 6 E
The churn drill ................ 7 ' f
The hammer-and—drill ............. 10 1
The Empire drill ............... 11 §
Transition to mechanical drills ......... 12 g
Factors retarding mechanization ........ 15 %
Extension of mechanization .......... 17 -g
III. ROCK DRILLS USED UNDERGROUND ........... 18 tai
The piston rock drill .............. 18 id!
Development of the piston drill ....... . 19 pf
Disadvantages of the piston drill ....... 22 ji
Hammer drills ............... . . . 24 Qi
Hammer—drill development ........... 24 4.%
Types of hammer drills ............ 25 ·`T
The drifter drill .............. 25 ‘_§
The stoper ....... . ......... 28 ,'
Hand—held hammer drills ........... 31 isp
The plugger ................ 32 ~`§
The jackhammer .............. 32 Z 5
The power auger drill .............. 34 ~q
he
Changes in motive power, materials, and parts. . 37 x A
Changes in motive power ............ 37 , E
Changes in materials and parts ........ 39 y T
Improvements in drill steel ......... 39 S
Changes in the shapes of drill bits ..... 44 E
Detachable bits ............... 45 i
IV. DEVELOPMENT OF SURFACE-DRILLING TECHNIQUES .... 49 5
Y!
Prospecting drills ............... 51 Q
The power churn drill ............. 51 T
Modern churn drills ............. 55 E
Rotary-type drills .............. 56 `§
The diamond drill .............. 56 lg
The calyx drill ............... 63 E
The hydraulic rotary drill ......... 65 {
5
vii ?
 
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  · viii CONTENTS
3 V Chapter Page
E-. Blasthole drills .`.............. B9
§_· Blasthole drilling in general—type quarries. . 7O
Q 1 Motive power ................ 71
`*· The piston drill .............. 73
x
f`i The portable churn drill .......... 74
if The drifter drill .............. 77
§
i Drilling and cutting in dimension-stone
@,` quarries ................. 79
i' Hand drilling ................ 79
£ g Rotary drills and modifications ....... 30
5 Piston drills ................ 93
; “ Hammer drills ................ B4
Q Special dimension-stone quarry machines. . . 95
q: The channeler ............... 85
T T The wire saw ............... B8
_l` Elasthole drilling in open-cut metal mines . . 90
‘£ Blasthole drilling in open—cut iron mines. . 90
Q Blasthole drilling in open—cut copper mines 95
*j¥ Importance of variety of drills ......... 108
i V. PROGRESS IN OUTPUT PER MAN IN ROCK DRILLING .... 110
2 Difficulties of measuring output ........ 110
‘_. Factors affecting footage drilled ........ 111
:_‘ Rock or ore characteristics .......... 111
al Effective drilling time per shift ....... 113
E Depth, inclination, and diameter of hole . . . 115
'i Removal of cuttings .............. 117
§»` Air pressure ................. 117
i-I Shape and quality of drill bits ........ 118
Q Skill of driller and management ........ 119
i Changing footage per man-shift in rock drilling 120
i Underground drilling ............. 121
1 V Hand drilling ................ 121
J Piston drilling ............... 121
Q ; Hammer drilling ............... 122
i.: Surface drilling at mines and general-type
*’ quarries ................. 123
Q · Prospect work ................ 123
3 * The diamond drill ............. 124
3 The calyx and shot drills ......... 124
i q The churn drill .............. 126
i"` Blasthole drilling ............. 129
iw Hand drilling ............... 130
i V Piston drilling .............. 130
§ Hammer drilling .............. 131
§_ Churn drilling .............. 181
iig Summary of surface blasthole drilling rates 132
E A Drilling and cutting at dimension—stone
{ quarries ................. 133
E Hand and ordinary power drills ....... 133
g' Channeling machine ............. 135
{ Wire saw ............. . .... 136
%.
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CONTENTS ix  
A
Chapter Page g
VI. ROCK-DRILLING PROGRESS AND EMPLOYMENT IN MINING. . 138 3
;{
General character of technological advance l
in rock drilling .............. 138 i
Volume of employment .............. 140 _ E
Changing occupations and skills ......... 142 E
Relative decline of drilling labor ...... 143 f
Changing skills ........ . ....... 144 `-{
l
Health and safety ................ 148 §
Outlook for employment in drilling ....... 153 E
L
s
5
CHARTS AND ILLUSTRATIONS {
Figure E
` E
Modern jackhammer drills at a surface {
operation ................ Frontispiece i
1. Drilling with a hand auger ............. 7 §
1
_ 2. Hand churn drills ................. 9 i
3. Double—jacking underground ............. 11 ` ¥
4. Couch's rock—drilling machine ........... 13 Egg
5. Later models of the piston drill .......... 21 ·p%
6. Late—model drifters in an American gold mine .... 28 fi
7. Automatic—rotating wet stoper ........... 29 K;
B. A wet jackhammer in an underground mine ...... 33 ¤.§
9. A jackhammer auger in an iron mine ......... 37 jh?
10. A 4-wing cross bit forged on hollow drill steel . . 44 é
11. Handling drill steel underground .......... 47 _-§
12. Two stages in churn-drill development ....... 54 _.€
13. An early portable American diamond drill ...... 58 · Q
14. A recent one-man portable diamond drill ...... 82 ME
15. A battery of calyx drills ............. 85 g g
16. Modern portable hydraulic rotary drill used for ~ 8
prospecting ................... 67 _
é
17. Early piston drill in a quarry. . .... . .... 73 j
18. Derrick—mounted drifter drill ........... 78 Q
19. A modern bar channeler in a granite quarry ..... 81 é
20. Direct-acting channelers .............. B7 i
21. Wire saw in a slate quarry ............. 89 Q
22- Electric churn drill at an iron mine. . . . .... 94 Q
23. Toe—hole drilling at an open~cut copper mine .... 98 .E
24. A steam—driven traction churn drill sampling ore E
at an open—cut copper mine ............ 108 §
25. A western hand—drilling contest .......... 146 g
E
a
 
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Ei » X c0NTENTs
g _ CHARTS AND ILLUSTRATIONS—Continued
Q °` Figure Page
]% . 26. Drilling in cramped quarters with a wet stoper. . . 148
$`_ 27. Upward trend in drilling speeds indicated by
gy results achieved under test conditions ...... 155
ii 1
%,j TEXT TABLES
!` Table
;   1. Chronology of introduction and adoption of A
3 ~ rock-drilling machines in underground mining
‘ in the United States ............... 14
_: 2. Chronology of introduction and adoption of
° V rock—drilling and cutting machines for surface
.i_ work in mining and quarrying in the
ip United States .................. 15
Q 3. Amounts and properties of some drill—steel
”Qi — constituents ................... 42
` 4. Cost of drilling and reaming with hand, steam,
and compressed-air drills at an Ohio quarry . . . 72
{ 5. Current use of major types of power drills
,2 and cutters ................... 1OB
Eid 6. Variations in hardness of material related to
C i` drilling speeds at the Soudan Mine, Minnesota,
§~ 1939 ....................... 112
g` 7. Relative output per driller-shift in blasthole
1-· drilling in open—cut workings as measured
Ep by volume of hole ................ 132
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PREFACE Q
This Project's reports have repeatedly pointed out that the kinds of i
technical changes introduced and the rates at which they have been in— i
corporated into industrial practice have had important effects on the i
volume of production as well as of employment. ln the extractive in- E
dustries advances in the methods used in drilling operations have been E
an important feature of these changes. Progress in this aspect of min- E é -
eral technology has affected all the mineral industries and has been i
l closely related to technological developments in such other phases of i E
mine operation as loading and transportation of ore and rock. The de- §
velopment of drilling technology in the bituminous—coal industry and in E
petroleum and natural—gas production has been covered in other National ‘ E
Research Project reports.l This report deals with rock drilling in other E
important mineral industries. cl
The first rock—drilling machines, though heavy and cumbersome. brought i
about enormous increases in the output per driller. As the machines were it
improved, as new types were developed, and as nanagement and labor became i"%
familiar with them, their use became general in the mineral industries. ,Yl
By 1909 all the basic types now used had become available. Further tech— pg
nical progress centered on improvements of motive power, materials, and `§
parts and the adaptation of machines to the requirements set by the yi
widely different conditions encountered in the various types of mining. _?
These later types of change are believed to have had, in the aggregate, g
as large an effect in increasing the productivity of drilling labor as jj;
did the initial shift frcm hand to machine work. fg
Advances in rock—drilling technology and gains in drilling productivity i 5
have been closely related to technological progress in such other mining E
operations as blasting, loading, transportation, and methods of extrac— p E
tion. The direct relation between rock—drilling mechanization and mining . E
employment is therefore difficult to trace. The immediate result of the g
increased output per man in drilling tended to be a contraction of total g
employment, but this has been largely offset by other factors. ln the E
first place, the lower drilling costs which have resulted from mechani— j
zation and the improvement of equipment have been an important factor in  
the vastly increased mineral production. This production increase, vital ` é
——  ii
lwillard E. Hotchkiss, F. G. Tryon, and Others, Mecizanization, Employment, and  
Output par Man in Bitwninous-Coal Mining QQPA National Research Frcject in comers- gg
tion with U. S. Department of the Interior, Bureau of Mines, Report N0. E—9,  
Aug. 1939); O. E. Kiessling, H. O. Rogers, and Others, Technology, Employment, ard .
Output per Man in Petroleum and Natural-Gos Production (HFA National Research Q
§;ggIe€tNOl·nEc-q%pepi§}iop9gv91)th U. S. Department of the Interior, Bureau of Mines,  
xi §
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   " " ’ ` ‘ · v_ _ _, _ _  _____r r___ _, -  i  V V   {EE · Q.  
 
i} I . .
  ‘ x11 PREFACE
g _ in supplying the needs of an expanding industrial economy, increased the
§_.` total amount of drilling to be done. Another offsetting factor has been
E'- the long—time tendency for grade of ore to decline. After the richest
ii. ores are exploited, a proportionally greater amount of drilling is re-
;;· quired to obtain a given quantity of commercially useful product from
i progressively lower—grade deposits. Similarly, as the most accessible
g‘. deposits are mined, a greater volume of drilling is necessary to remove
$`p overburden or to develop underground workings. These tendencies have
Q M operated in the past and may be expected to influence the volume of
  drilling labor in the future.
l_j This report was prepared by C. E. Nighman, of the National Research
A i Project, and O. E. Kiessling, of the United States Bureau of Mines, as one
ini of a series of studies conducted by the National Research Project in
l cooperation with the Bureau of Mines under the direction of Dr. Kiessling.
1
f T The manuscript was edited and prepared for publication under the direc—
i` tion of Edmund J. Stone.
I Divin Wrinranua
ill; PMILADELPHIA A
N·i February 6, 1940
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ACKNOWLEDGMENTS i
Acknowledgment is made of important assistance given by officials of §
the U. S. Bureau of Mines. Helpful suggestions and criticisns were supe i
plied by Charles F. Jackson, Chief Engineer, and McHenry Mosier, Senior g
Mining Engineer, Mining Division; and by E. D. Gardner, Supervising A {
Engineer, Southwest Experiment Station, Tucson, Arizona. Information é
` regarding technical aspects of nonmetallic operations was kindly fur- - é
nished by Oliver Bo les, Assistant Chief Engineer, Nonmetals Division. §
Data regarding the effect of drilling practices on the health and safety I g
of workers were supplied by Daniel Harrington, Chief, Health and Safety i
Branch. W. W. Adams, Supervising Statistician, and M. E. Kolhos and {
Virginia Wrenn, Employment Statistics Section, gave major assistance in ; E
assembling material on employment and accidents in mines and quarries. {
Mabel E. Winslow, Information Division, read the manuscript and suggested é
mmmom mpmwwems. §
The following members of the staff of the WPA National Research Project _·§
made contributions that are not otherwise noted. P. J. Wester, Marguerite a %
lane, and L. D. Nierenberg carried out special assignments connected with QQ
the preparation of the manuscript. Cooke Settle prepared the graphic lg;
material. r`I
Thanks are also extended to Dr. R. R. Sayers, Chief, Industrial Health °§
Division, U. S. Public Health Service, who gave many suggestions re- Pkg
garding the health and safety aspects of rock drilling that were help— 5
ful in the preparation of the study. Indebtedness is also expressed to _?
F. G. Tryon, Chief, Research Section, Bituminous Coal Division, U. S. A?
Department of the Interior, who served in a consulting capacity during I 5
the initial stages of the study. I E
Manufacturers of rock—drilling and quarrying equipment generously sup- i  
plied test and operating data and many of the photographs that have been · E
incorporated in the text. The cooperation of the following concerns 3
is cordially acknowledged; Bucyrus—Erie Co., South Milwaukee, Wis.: é
Chicago Pneumatic Tool Co., New York, N. Y.; The Cleveland Rock Drill E
Co., Cleveland, Ohio; Gardner—Denver Co., Quincy, Ill.; Howells Mining §
Drill Co., Plymouth, Pa.; Independent Pneumatic Tool Co., Chicago, Ill.; §
Ingersoll—Rand Co., New York, N. Y.; Jeffrey Manufacturing Co., Columbus. Q
Ohio; Keystone Driller Co., Beaver Falls, Pa.; and Sullivan Machinery ii
Co., Chicago, Ill. E
é
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· INTRODUCTION {
l
The transition from manual to mechanized drilling and the subsequent i
improvement of rock drillsl have been among the most important technical  
I
advances in mining and are closely related to the changing character of {
the mineral industry in the United States and to the development of other {
aspects of its technology. Progress made in the art of drilling is one E
of the most important reasons why it has been possible to meet the demand i
5
for minerals at constantly lower relative prices.2 The success of ap- {
plied technology in reducing unit drilling costs, which are chiefly labor é
. . ~§
costs, followed from the greater volume of output resulting from each g
,1
unit of labor spent. Other reports of this series of Mineral Technology E
and Output per Man Studies discuss the relationships between the changing TE
demand for minerals, technological progress, and employment opportunity ¥
in the various branches of mining. Insofar as drilling improvement de- 1;
creased the unit labor requirements it is of special interest in inter- · `¥
preting the record of rising output per man and of changes in total `QQ
labor requirements that acconpanied technological progress in the mineral ii
industries. ; i
.%
THE STIMULUS FOR DRILL MECHANIZATION  
With the great expansion of the railway network in the latter third §
of the nineteenth century, engineers found it advantageous to bore rock .§
tunnels in overcoming obstacles of terrain. Such work, hcwever, was time- i M;
consuming and costly with the hand methods then in vogue, and railway- 3 5
tunnel construction provided a great incentive for the development of . g
a mechanical drill. About the same time the development of the west- E
ern bonanza metal deposits provided a proving ground for underground · g
drilling machines in mining. However, as the bonanzas were soon depleted i g
and few new rich deposits were found,attention turned to the pcssible §
exploitation of the lower—grade ore deposits. These deposits represented i
the large—tonnage resources required by an expanding industrialism and i
S
· Note.- The authors are grateful to H. P. Sweeny, R. L. Kiessling. and E. Weinberg,  
respectively mining engineer and research associates of the WPA National Research ;
Project, who conducted extensive background studies utilised in the preparation  
of this PEDOTT,. Qi
lillthough the early manual drills were rock drills in a strict sense, the terms  
"rock drill" and "rock drilling” are employed in this discussion as commonly used .{
to connote power rock drills and the act of drilling with them. :§
ZF. G. Tryon, T. T. Read, and Others, Technology ami the Mineral Industries (NPA  
National Research Project in cooperation with U. S. Department of the Interior, 5
Bureau of Hines, Report No. E-1, Apr. 1957), chart 2, facing p. 4.  
1_ i ` ' T Q
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..... ._ *5

   ‘ t   eeee    c is c ,__ - »  I _  3.    
g ,
  I 2 ROCK DRILLING
gt they could be successfully exploited provided the costs of mining were
g ·, reduced. Since, under the hand methods prevailing in the seventies,
;_' drilling constituted the major fraction of total mining costs, mechani-
ggr zation of the drilling operation provided a very great opportunity for
§, cost reduction.
gg- A few examples will help to illustrate the importance of hand drilling
Q with respect to both mining ccst and labor required, in mining as it was
i Z practiced more than a half century ago. ln 1874 Professor Spilsbury
Q ~ pointed out the "crying want of the Western miners for some cheap and
5 effective machine, capable of economizing on the heavy item of hand- -
A J drilling ..... " Reasoning fr m European experience, Spilsbury said
A * "fully twcethinds .... of the entire cost of mining is consumed by th