Prep,.int for the New York Meeting, February, 1940 Permission ia hereby given to publish with appropriate acknowledgment, excerpts or summaries of this

P r e p k t not to exceed one-third of the eniire tezt of the paper. Permission to print i n more eztended form subsequent to publication by the Institute must be obtained from the Secretary of the Institute.

ARIERICAN INSTITUTE O F MINING AND METALLURGICAL ENGINEERS

Technical Publication No. 1172 ( C ~ a a s A. METAL RIININO, NO. 116)

DISCUSSION OF THIS PAPER 18 INVITED. It should preferably be presented by the con- tributor in person at the New York Meeting February. 1940 when an abstract of the paper will be read. If this is impossible discussion in wri'ting (2 copies) &ay be sent to the Secretary, American Institute of Mining and,~eiallurgical Engineers, 29 West 39th Street, New York, N. Y. Unless special arrangement is made, discussion of this paper will clone July 1, 1940. Any discussion offered thereafter should preferably be in the form of a new paper.

Use of Diamond-impregnated Cemented Carbide for Core Bits

(New York Meeting, February 1040)

AN extended program devoted to the development of a matrix for holding diamonds of a size and kind not heretofore generally used is being carried on by the Carboloy Company, and this paper describes the part of the development that affects mining and its allied industries. Labora- tory and field work so far has indicated the following:

1. Tungsten carbide and cobalt form the most desirable known matrix material for the holding of diamonds for drilling work.

2. Industrial bort diamonds in sizes and of a class not generally heretofore acceptable and therefore less expensive can be successfully held in this cemented carbide matrix.

3. In exploratory drilling, the combination of bort diamonds, impreg- nated throughout a matrix of tungsten carbide and cobalt, when fabri- cated onto drilling crowns, is an indicated economic substitute for drilling crowns in which the diamonds are set by hand, mechanically or by casting.

4. This impregnated type of drilling crown or bit has definite possi- bilites of revolutionizing the drilling of blast holes, particularly in the harder formations. This will be brought about by the development of high-speed light-weight rotary equipment using an impregnated diamond bit to replace the percussion drill now in general use. (The development of this rotary equipment is well past the laboratory stage at this time.)

5. That the use of a rotary bit is a preventive measure in the fight against silicosis.

The development of this product was started by G. F. Taylor a t the Research Laboratories of the General Electric Co. I t was early recog- nized that it had possibilities in the drilling field and the present product is the result of considerable experimental work with other powdered metals as well as with tungsten carbide and cobalt.

In the study of the potential application to the mining field, i t was learned that carbon diamonds originally were given a high rating of performance but that the trend had been toward borts in selected sizes

Manuscript. received at the office of the I~istitute S o v . 27, 1939. * Engineer, Carboloy Company, Inc., Detroit, Mich.

- . - - Copyright, 1940, by the American Inntitute of Mining and Metallurgical Engineers, Inc. AIINING TECHNOLOOY, March 1940 Printed in U. S. A .

2 DIAMOND-1JIPREGN.ITED CEMENTED C-YRBIDE FOR CORE BITS

and quality. During the past few years this trend has been accelerated. although today much smaller and less expensive stones are in general use.

There is also a change taking place in the methods used for setting diamonds for drilling work. Hand setting has been the popular method for many years but today cast setting and mechanical setting are used. The cast-set method involves the casting of a molten mass such as brass, certain of the nickel alloys, etc., around diamonds that havc been prc- positioned. The mechanical method involves the setting of a surface layer of diamonds in a powdered metal, and might also be said to include the method used in the manufacture of so-called diamond-imprcg- nated products.

Unquestionably all of these methods will have a place but where only a surface layer of diamonds is used, it is indicated that a selection of diamonds must be made to assure proper shape for maximum holding. In diamond-impregnated products it is not so essential that the diamonds meet the <ame standards of quality as are necessary with other setting methods, for the reason that a great nlultiplicity of cutting points are made available a t the cutting surface and therefore the failure of one or more points is not a serious matter.

The development of cemented carbide matrices for the holding of diamond particles is therefore another step in the evol~itioil toward the economical use of smaller diamond particles in types and kinds not heretofore usable. The ccmented carbide matrices havc qualities that make then ideal for holding diamonds. such as ability to withstand abra- sion and lo\$- coefficient of c~xpaosion.

Diamond-impregnated products have been commercialized for such purposes as grinding-wheel dressers, optical and other glass laps, glas. drills, small grinding wheels, center laps, etc. For such application- diamonds in sizes from 8-mesh to 425-rnesh havc been n s ~ d .

During our lal~oratory and field cxpcxriments we h:lvc tested a \viclv variety of nlatriceq, so that totlay M t3 Iiave available a range from hard to soft in nhich diamor~d l~articles frorn 8 to 48-mtlsh have be~r i succrsr- fully bonded together and used. This range of diamond sizes and matrix variations, n hen properly combined, should prove of distinct advantage for drilling various rock formations, although it is hoped that a minimum number of combinations tird in with a resharpening technique, to be described later, will suffict,.

The nlannfac~turing process consists essentially in mixing diamond particles in exact proportions with tungsten carbide and cobalt in powder form. This mixture is the11 placed in molds and heat and pressure are applied simultaneously. As removed from the mold, the diamond-

W. C. WESLOW 3

impregnated mass is ready for attachment to the steel bit blank. A com- plete assembly is shown in Fig. 1.

At first, it was found difficult to balance the rate of wear of the matrix material with the diamond wear and a t the same time maintain a fast cutting rate. Also, there were problems of maintaining gauge and. clearance.

I t is indicated that the solution lies in the direction of using dianiond particles of the proper size for the formation being drilled, and the hardest possible matrix combination. The use of the hardest possible matrix combination assures maximum resistance to abrasion and therefore

FIG. 1. FIG. 2. FIG. 1.-DIAMOND-IMPREGNATED CEMENT CARBIDE CORE BIT. FIG. 8.-SANDBLAST UNIT FOR RESHARPENING CORE BITS.

maximum life. This combination, however, tends to decrease the cutting rate in that the matrix material does not wear away fast enough to give proper cutting clearance for the diamond particles. This has been over- come by introducing an inexpensive resharpening method that can be used periodically to resharpen the bits.

The need for resharpening varies with the formations being drilled; some are more abrasive than others and tend to keep the matrix material cleared away from the diamonds. The operating conditions also play a part in determining when a bit should be resharpened. So far, the resharpening feature has been economical and desirable.

The resharpening process utilizes a small, compact, inexpensive sand- blast unit that was developed for this purpose (Fig. 2), composed of a

4 DIAMOND-IMPREGNATED CEMENTED CARBIDE FOR CORE BITS

blast cabinet, dust-exhauster motor and dust-collector bags. There are very few wearing parts, which holds upkeep low. The installation and operation are simple and can be accomplished by the average mechanic.

The operation is illustrated in Fig. 3. The unit is equipped with a Jg2-in. air jet and a $4-in. nozzle through which Xo. 180 silicon carbide abrasive is forced, using 35 to 40 lb. of dry compressed air, requiring approximately 5 hp. The time required for re- sharpening varies from 2 to 5 min., depending on the-condition of the bit.

This combination of hard ma- trix, Dropcr diamond size and

, A A

resharpening allows over 75 per cent of the original diamond content of the bit to be worn away before the bit is discarded.

Our laboratory experiments and field work have been in the main conducted on rhyoIite and diabase from Koranda mine, a t Noranda, Quebec, Canada; iron ore, jasper and country rock from the Soudan mine of the Oliver Iron Mining Co. at Tower, Minn., and limestone and sand- stone. These rocks are thought to represent a fair proportion of the types that might be found throughout the world and therefore the result of our work can perhaps be applied to other fields.

We set up in our own plant a conventional Longyear Junior drill rig with an electric motor mounted on the frame and with hydraulic feed mechanism. Many tests were run on the types of rock mentioned and, while not conclusive, the results were very indicative. Observations were made on the effects of speeds in relation to pressures, rate of wear of one type of matrix against another, comparison in cutting rate of various diamond particle sizes, power requirements under the various conditions, etc. Detailed results from these tests are not given here because the work in the field is thought to be more conclusive and particularly because the field results confirmed to a marked degree the laboratory work. How- ever, as an example of the type of information that can be obtained from these laboratory tests Fig. 4 is shown.

W. C. WESLOW 5

FIELD RESULTS Olivrr Iron Mining Company, Soudan Mine

I t is said that at this mine the world's most severe drilling conditions cxist, due to the extreme hardness of the iron ore and jasper formations. After some preliminary work, which showed promise, arrangements were made to do a thorough job of testing the diamond-impregnated bits by setting up a new drilling machine with an engineer in charge to drill holes ~lnder a variety of co~lditions such as speeds and pressures. From these tests, which iilvolved some 34 bits, speed ranges from 145 to 2000 r.p.m.

RP.M.- 1130 1130 1130 1400 1400 1400

TOTALRIT PRCJ3URE-1168 1753 2337 1166 1753 2337

FIG. 4.-TESTS RUN IN LABORATORY ON RHYOLITE.

and pressures ranging from 934 to 4672 lb. on the bit, considerable data have been gathered. Table 1 shows a test sheet complete through the life of one experimental bit. I t is to be noted that the speed was kept co~lst,a~lt at 1000 r.p.m. Fig. 5 describes a series of tests with one bit in which speeds and pressures were varied. I t is to be noted that at low speeds and high pressures the cutting rate is low and the bit wear exces- sive. Fig. 6 shows comparative results obtained under varying speed and pressure conditions.

To date the indications are that best rezults will be obtained with diamond-impregnated bits in the drilling of this ore at spindle speeds of 1000 to 1250 r.p.m, and a t total bit. pressures from 1520 to 1753 lb. This combination produced a satisfactory minimum of bit wear and

6 DIAMOND-IMPItEGNATED CEMENTED CARBIDE FOR CORE BITS

ROCK AND ORE. Total distance drilled, 52.1 ft .; average feed, 1.26 in. per inin.; total nulllher or

tests, 26.

W. C. WESLOW 7

maximum footage before resharpening was necessary .and also reduced to a minimum the polishing action on the diamonds.

In the experimental work, it was noted that unbalanced wear occurred between the inside and outside diameters of the bit, which was thought to be mainly due to the difference in surface speed between the two diameters. This was overcome by so designing the diamond-impregnated portion that the diamonds were properly distributed. Core blocking was reduced to a minimum by the reduction in size of the waterways and by reducing the water pressure to 50 pounds.

For the purpose of arriving at costs that might be expected, life tests were conducted on bits that incorporated all the best features known a t

that time, also life tests were made on bits that incorporated some untried features. These bits were tested on a Longyear Junior drill rig operating at 1000 r.p.m. and 1635 to 1753 lb. total pressure. The results on a few of the bits are shown in Tables 1, 2 and 3.

The main difference between bit No. 1-K (Table 1) and bit 99-J (Table 2) is in the length of diamond-impregnated material. Bit 1-K had approximately 50 per cent more diamonds than bit 99-J, and it is interesting that bit. I-K did about 50 per cent more in total footage. Fig. 7 shows these actual bits with the starting and finishing dimensions as well as original and final cores.

Bit 32-K was made up to prove the merits of a soft versus a hard matrix and with this exception is directly comparable to bit 99-J, which

~.

.----

. . -~

. -

-

. --

-- . -

dm

+

NN

N-

N

mn

- O

OC

8

88

8g

8

8

0 0

0

- . --

-~

-

- +

3

0

3 -

0

0

0

c

0

. .

. .

--

PA

--p

~

1 ~

~~

m'

-?

o?

~o

mm

~m

~~

h?

~~

?y

~"

t?

~g

~c

-?

~~

a?

+-

-?

~

+~

~~

.%

mm

aa

aa

~~

~-

~o

nm

~~

h~

-~

cr

-+

-~

cm

1

.w 5

%

Z8

Z2

bB

gM

-

m-

cr

oo

cm

mc

c+

t-

0c

;-

.+

=r

-t

--

?~

,0

+

26

.*

--

-

34

-+

--

-

++

- +

-

...................................

mb

$b

bb

bj;2

jb

~h

bb

~b

b~

;n

it,b

:~

j

j;oS

jBbtbbb

."?

?"

?c

."~

"

I"

.."-

P!i?

Y:!s

??

L?

. r

i

.*

? 0

rn

a.

ni

~i

;i

~>

~&

~*

~j

~~

i>

i~

i~

+~

i~

~i

li

i~

ii

-

1; h

3m

J.

t-

~L

:~

~s

~C

^I

'r

~c

fl

2(

3~

~W

~Q

'3

~^

~?

d:

*~

.I

.r

~-

.1

7~

?*

C1

-*

1-

%

OC i z I

al

bC .z 2 '0

2 m i

C"

Y

.3 24

Sae

F *

k

3 2 q P

e-

c r

-

mo

c

E3

C

TABLE 2. - -Com,p i l u t i on Core-bit Life 'I'ests NAME OF (:OMPhNY Oliver Trorl -- Minirr~r ~ Co. EQUIPh lENT Longyear (1. -

LOCATION 'rower, - Minnesota - - . POWER Electric ~ -

NAME O F MINE Snuda11 - -~ - Hydraulic - FEET) - - -~ ~ -

FORMATION Ore -- - - W.lTICIL PRICSSURE - 5 0 l h :

HIT Nlihll3l~:l< ~ !I!)-.I - - (;-2572 -- DIT SIZES

INSERTS 6 I J VI.:SH 1.1 a o (:ODE; -~ .5-N-14-20 / Start ~' i l~isll I , o ~ >

-- --

. . - - - - - - ~ - - ~- - -

. . . . . . . . . . . . . . TYPE OF 1311' - ~ - ~~

0 . L ) . 1 480 / 1.412 0 .048 . . . . . . . . . . I . n I 0.963 0.118

ST!\RTEI) _-!-13:3'J CO31PLETF:L) - 3~17-39 - L e ~ ~ g t h . . . . . . . . . . . . ; 1.858 ) 1.681 0.177 I I

1I.I.C. 0.220 in., r..p.rn. 1000 wit11 1650 to 1750 Ih. pressure on bit I I I I I I I

Inches Bit I,OAS. Ill. Aver- r e s t Elawed ,,.. Drilling "2: 1 Inches 1 -- .,

Time i n Time h4inute Ilrillcd 1 I

ZZ tests 22.15 111.. 18'3.88 f t . " sll. sl?lldblil~tirlg to I 1 . ~ l l i l l ' [ ) l , l l .

1, 8 .13 It. r,er r r r . l ~ a ~ . ~ , ~ n i r l ~ . 8 . 5 7 ft. 1,i.r ho11r PI:I$ISPII tixllc.

'I'ABLE 3.-Compilation Corc-bit Life Tests h'.i.\lb; ( . ~ > ~ p ~ x y Oliver I IVI I h l i t~ ing C:ol EQUIPI\.IENT ) . O I I R Y P ~ ' - I:. ( : .

~- - - --

Tower, iVlilrnesota. r,OC.i'rION _ . -- POWER - - Electric -

Soudarr NAME O F MINE - F E E D Hydraulir Ore FORMA'rlON - ~ - -- - - - WATER PRESSURE 2 n l I l . --

BIT NUMBER _ 32-K G-2572 - BIT SIZE<

INSERTS lj GRADE E-_ AIESH - 14-20 --I

5-P-14-20 CODE - -. ~ - I S ta r t I I'inidi

W.4TERWAlrS u352 x % n ill. -~ -

- ~ -- ~ - I - ~~- I -- ~ a

I l.osa ! _ _ - ~

. . . . . . . . . . . . . . TYP E OF BIT > X p p ~ ~- O . D . . / 1.463 I 1.431 0 .032 I .D . . . . . . . . . . . . . . . 0.850 . 0.889 0.030

STARTED 2-13-30 C:OMPI,ETED 2222239 ~ e n g t l ~ . . . . . . . . . . . . . / 1.937 1 ,762 I 0.175 I 1

Il.1.C. 0.220 in., r.p.m. 1000 with 1650 to 1750 Ib. pressure ori'bit

Hit Loss. I n . I I .Av"r- - . :rge

~ ~

I 11 tests 9 . 2 2 111.. 80 .01 f t .

7.27 ft. per rrconditioni~~g. 8 . 6 8 ft . per hour elapsed t i ~ n e .

0 ST3 c:~~ldblart,ing t o resharpen.

10 DIAMOND-IhlPHEGNATED CEMENTED CARBIDE FOR CORE BITS

had a hard matrix. The over-all bit life of So . 32-1< was poor, probably because of the softer inatrix.

A tentative estimate indicates that a marked cost improve~nent call be expected if diamond-impregnated bits are substituted for thc prcsu~lt method of drilling a t this mine. Table 4 gives these estimated results.

TABLE 4 . - K ~ s u l t s (f ~ J I P s ~ s Cornparing Drilling Speeds [f J~nck Bits nnrl Diamond-impregnated Bits

1 Inches Drilled per Minute ' Fo~.matiut~ I~lcrensed I ) r i l l i l~g 1 Jack Bits 1 D.I.C. Bit. 1

1 I I

a Limitations of drilling equipment prevented D.I.C. bits from drilling at a snb- stantial incrcnse in spectl. Were greater speeds possible, a more favorable cost comparison should result.

The experimciital ~vorli a t Sottdau rninc represents about 9 montl~s of work, during which time approximately 1320 ft. of drillir~g was done in ore. Thc results are so cnoouraging that thc iiii~)c management has ordered tn-o new spcciallv dcsigllcd drilling mnc~hines to be used in a productive way. Table 5 summarizc~s the tcsts.

1 ,226 465 1.422 1 238 1.712 39° 0 . 6 8 i 112

Hardest ore. . . . . . . . . . . . . . . . . . . . . . . . . . I 0 .217

Results t,o dittc: have: indicntcbtl rllnt tlianlo1id-i1il~)reg11atcc1 hits ( ~ 1 1 1

suc~cessfully compete ~vith carboll ))its ill drilling snr~dstor~e. The sailclstone drillcd to date. llas bren very abrasive and has tlic.

effect of abrading t'he holding ma'terial around the diamonds. The suc- cess of the diamond-impregnatcd material is primalily due to the fact that t'he cemented matrix i:: resist,ant to this type of abrasion. Incidentally, in this type of formntio~i there is 110 need for resharpening ns the rate of wear on t,he matrix is such tliat thc diamo~id part,icles arc: continually exposed.

Experimental work in drilling limeston(. is being continued, as it 11:l.s

not yet bceri possible to maintain n satisfactory rate of cutting. Thct field work a t the time this paper is prepared has been without the use of a sandblast unit for resharpening and as this is no\\- in t,he process of bc:ing installed, favorable rcsults are expected.

Average ore. . . . . . . . . . . . . . . . . . . . . . . . . . Softest ore. . . . . . . . . . . . . . . . . . . . . . . . . . . Hardjasper . . . . . . . . . . . . . . . . . . . . . . .

Noranda Mines, Lld.

0 .420 1.226 0 32

Noranda mine has been very progrctssil-c i l l tlie development of new methods for blast-holc clrilling and is now using dittmonci bits for thi.;

W. C. WESLOW 11

purpose. The development has been described1 and no additional details are necessary here.

At this mine, a number of bits have been on test and recently a sand- blast unit for resharpening has been installed. Recent reports on the performance of diamond-impregnated bits at this mine show considerable promise and the work is now being expanded for the purpose of obtaining life test data on a considerable number of bits. Table 5 summarizes the tests.

TABLE 5.-1)rilling Results

Limestone Sandstone. Rock. . . . .

. . . 900

. . . . . 900 . . . . . . 1,500

0.003 None

0.0007 0.0003 0.0003 0.0014 0.001

4. Rhyolite.. . . . . . . 5. Diabase.. . . . . . . . 6. Ore. . . . . . . . . . . .

1 , 1 6 8 ) 2-7 1,975 100 0.0002

0.0006

Formations Nos. 3, 6 and 7 from Oliver Iron Mining Co.: fornlations Nos. 4 and 5 from Noranda Mines. Ltd.

1,000 1,000 1,000

1,753 1,168

I t is indicated that, to obtain maximum performance from diamond- impregnated bits in exploratory work, some consideration should be given to improvement in machine and equipment performance, particu- larly in the direction of higher speeds with improved feed control. The lessening of vibration would also be helpful. As short-hole drilling with diamond bits is relatively new, not much in a definite way can be said about machine requirements, but it can be stated that in order to compete with the present percussion drilling equipment, it will be necessary to develop light and portable equipment that will be designed to operate a t high speeds and with minimum vibration.

These improvements will no doubt also necessitate improvements in chucking devices, rods,.core barrels, et cetera.

The following favorable factors accompany the use of diamond- impregnated hits: (1) no resetting problem; (2) a minimum of 75 per cent utilization of diamonds present in a bit; (3) in blast-hole drilling, more holes or footage per man-hour, depending on rock formations and condi- tions; (4) reduction in the amount of rock to be drilled as well as decrease in starting size of the hole as compared to drilling with a steel bit; (5)

7. Jasper.. . . . . . . . . . 590

- -

'0. Hall, R. V. Porrit,t and A. D. Carmichael: Stoping at Noranda. Trans. Canadian Inst. Min. and Met. (1939) 42, 133-149; also Bull. Inst. Min. and Met. (London) (March 1939).

2-6 2-4

1,753

1,000

2.74 293.88' 1 8 .39 Not complete 1 . 5 3.000 10.375-0.920

0.00069 0.003

60-80 0.0003 850 50-70 0.0004

12 DIAMOND-IMPREGNATED CEMENTED CARBIDE FOR CORE BITS

possibilities for deeper holes due to no appreciable loss in gauge; (6) froin an operator's standpoint, less noise and vibration as well as freedom from dust.

ACKNOWLEDGMENTS

The author wishes to thank the personnel of the Oliver Iron Mining Co. and of the Noranda Mines, Ltd., and others who have assisted in this development for their interest, cooperation and patience during the experimental period of Carboloy diamond-impregnated core bits. Acknowledgment is also made to the Pangborn Corporation, Hagerstown, Md., for its cooperation in designing and producing a special sand- blast unit.