FIG. 6. Chip having abnormally high activity because 
of broken off piece of carbide tip. 
graph (7). (Bottom) Micrograph 
where it finally stuck. The size of 
this piece, calculated from the activity, 
was 15ug. An autoradiograph [Kodak 
autoradiographic plate (7)] and a mi- 
crograph are shown in Fig. 6. 
Counting efficiency. From irradi- 
ation and nuclear data, the specific 
activity of the tips immediately after 
the irradiation is 25 me/gm tungsten 
(corresponding to 10 mc/gm during the 
experiments). Comparison of this fig- 
ure with the activity of the reference 
sources, corrected for the difference in 
time, gives a total efficiency for the 
counting equipment of 12%, which 
within the limits of error is equal to the 
10.5% found when using a UX, stand- 
ard source. Of course, since the 
neutron flux is not known exactly, this 
check is only approximate. The error 
in the flux is probably < 20% (3). 
Autoradiographs. Because of the 
relatively low activity, autoradiographs 
of the work piece and turnings were not 
distinct. A work-piece autoradiograph 
is shown in Fig. 7, and another (one of 
the turnings), in Fig. 8. 
From Fig. 7, it is seen that the mate- 
rial transfer to the work piece is dis- 
tributed partly evenly (the faint lines) 
and partly discontinuously (the black 
spots). This region of spots and 
marked lines corresponds to start or 
finish of arun. This is verified by the 
fact that the axial distance between 
two such regions (one of which is 
shown) is equal to the length of the 
154 
(film: Ilford C) 
(Top) Autoradio- 
transfer of the tool during a 30-sec run. 
The autoradiograph of the turning, 
Fig. 8, is very faint but shows no 
marked discontinuities. 
Discussion 
This investigation confirms that, 
with these materials and cutting data, 
there exists a linear relationship be- 
tween the rake transfer and the turning 
time. If this relationship is obtained 
with other materials and data, it will 
be possible to make a comparison be- 
tween different qualities of carbide tips 
without machining until the cutting 
edge of the tip breaks down. 
A material-transfer-versus-time 
curve could be constructed after only a 
few runs of 30 sec each. The slope of 
this graph gives an idea of the cutting- 
toollife. However, if a group of curves 
of the second order, which do not inter- 
sect, is obtained, a comparison can be 
made by measuring the slopes. 
According to Merchant, the accuracy 
of the radioactive method is better than 
that of conventional methods, and, 
moreover, the cost of making a test is 
relatively low. Merchant has also 
shown that, when using cutting fluid, 
more than 95% of the activity is 
attached to the turnings. 
Merchant made the radioactivity 
measurements on all turnings formed 
during a very short period by means of 
a gamma-sensitive G-M tube, thus 
giving the sum of the activities on both 
FIG. 7. Avutoradiograph of work piece after turning 
FIG. 8. Autoradiograph of chip formed after 30-sec 
turning (film: Ilfex) 
sides of the turnings. The present 
method, however, gives the amount of 
material transferred to one side only, 
thus permitting separate investigation 
of each side. 
The authors wish to express their thanks to 
Professors R. Wozxén, head of the Div. of 
Mechanical Technology, O. Lamm, head of 
the Div. of Physical Chemistry, and O. An- 
dersson, acting Professor at the Div. of 
Mechanical Technology, .for their kind inter- 
est in this work and for placing laboratory 
facilities at our disposal, and Messrs. T. 
Westermark and G. Aniansson for prelimi- 
nary calculations and valuable discussions. 
Thanks are also due to Mr. C. Lindberg for 
skillful technical assistance. 
The nucleonic equipment used in this work 
was placed at our disposal by the Swedish 
Atomic Committee. 
The irradialions were made by AERE, 
Harwell, England, and the valuable help 
of Mr. J. L. Putman is also gratefully 
acknowledged. 
Health precautions were supervised by 
Dr. S. Benner of the Radiophysical Depart- 
ment, Karolinska Institutet, Stockholm. 
Further research on this method will be 
carried out at the Div. of Mechanical 
Technology, this being made possible by the 
State Council of Technical Research who have 
kindly placed funds at our disposal for this 
investigation. 
BIBLIOGRAPHY 
1. M. E. Merchant, E. J. Krabacher, J. Applied 
Phys. 22, 1,507 (1951) 
2. M. E. Merchant, H. Ernst, E. J. Krabacher, 
Paper presented for ASME, June, 1952, Cin- 
cinnati, Ohio 
J. L. Putman, personal communication 
AERE Catalogue No. 2 (Harwell, Eng., 1950) 
Amendment to AERE Catalogue No. 2 (1952) 
J. Cockeroft, Endeavour 9, 55 (1950) 
L.-G. Erwall, M. Hillert, Research, 4, 242 
(1951) 
ROBIE L 
