Wear Studies of Irradiated 
Carbide Cutting Tools 
Isotope-tracer measurements, more accurate than microscopic examination, show a 
constant rate of tool wear. 
With proper choice of isotope and specific activity, G-M 
and autoradiographic techniques can be used under normal machining conditions 
By B. COLDING* and L.-G. ERWALLt 
Royal Institute of Technology 
Stockholm, Sweden 
NEUTRON IRRADIATION of carbide ma- 
chining-tool tips provides a sensitive 
and accurate method of following 
cutting-tool wear. 
In normal operation, tool wear pro- 
ceeds more or less continuously. Mi- 
croscopic examination, which necessi- 
tates interrupting the machining, can- 
not demonstrate this constant rate of 
wear. Consequently, it is necessary to 
machine until the cutting edge breaks 
down or until the wear has reached a 
given amount. A microscopic investi- 
gation, involving the data in Table 
1, would require at least nine determi- 
nations at three cutting speeds because 
of the poor accuracy of the method. 
Merchant, using radioisotopes, has 
shown (1, 2) that a linear relationship 
exists between tool wear and length of 
machining time. Our investigations 
show that the transfer of irradiated tool 
material to chips and distribution of 
the material on the work piece can be 
accurately measured by Geiger-Miiller 
and autoradiographic methods. How- 
ever, counting-rate and _health-pre- 
caution considerations demand the 
proper isotope selection and optimum 
specific activity. 
Irradiation of Tips 
Two carbide tips—qualities 1 and 2 
in Table 1—were irradiated in a neu- 
* Division of Mechanical Technology. 
+ Division of Physical Chemistry. 
Side rake 
angle, 
yi 
+ 2 — i 
10° 
aI 
be 
ark Side Top 
endl a 
FIG. 1. Carbide-tip cutting tool characteristics 
TABLE 1—Machining Specifications for Test Runs 
Carbide tool composition 
Co (%) TiC (%) TaC (%) WC (%) 
Quality no. 1 (?4 3.5 2.5 86.8 
Quality no. 2 9.3 4.7 — 86.0 
Work-piece data 
Billet dia. 200 mm, Brinell hardness 220 kg/mm? 
C (%) Mn (%) Si (%) P (%) $8 (%) 
0.58-0.60 0.80-1.10 0.20-0.24 0.04 (max.) 0.04 (max.) 
Cutting data 
Depth of cut = 2.0mm 
Feed = 0.5 mm/rev 
Cutting speed = 100 m/min 
Tool geometry 
Nose radius = 1.0mm 
Clearance angle = 5° 
Side rake = 102 
Side cutting edge angle = 45° 
Nose angle = 90° 
Machine: Skoda SUR Lathe 260 X 2,000 mm 
151 
