Mar. 13,19x6 
New Penetration Needle 
1123 
needle to define would be one having a straight taper. Round, polished, 
annealed-steel drill rods having diameters of 0.042 inch were therefore 
cut into 2-inch lengths and pointed at one end with tapers having a length 
of and H inch. Each needle was tempered and highly polished, 
then tested in the penetrometer on a material showing a penetration of 
140 with the standard needle. The penetrations were as follows on 
needles made from 0.042-inch drill rod: ^--inch taper, 125; p^-inch taper, 
127; ^--inch taper, 129; 2^-inch taper, 134. 
Table I .—Results of a standardization test of penetration needles on oil asphalt 
[Accepted values 6.8, 6.9, 7.0] 
Needle No. 
Oil asphalt 1. 
Operator 
C. 
Operator 
F. 
Operator 
D. 
Operator 
A. 
Operator 
E. 
Oil asphalt 2. 
Operator 
C. 
Operator 
F. 
Standard. . 
1 (rejected) 
2 (O. K.)... 
3 (O.K.)... 
4 (rejected) 
5 (rejected) 
6(0. K.)... 
7 (rejected). 
8 (rejected). 
9 (rejected). 
10 (O. K.)... 
11 (O. K.)... 
12 (rejected) 
6.9 
7.2 
6.8 
6.9 
7* 1 
7.1 
6.7 
6.7 
6.8 
6.9 
6.8 
6.7 
6.9 
6.9 
6.8 
6.9 
7-3 
6.6 
6.7 
7-4 
7.0 
6 - 95 
6 - 95 
6.6 
6 - 5 
6.6 
6 . 75 
6 . 75 
6.85 
6.6 
6.9 
7.0 
7.0 
15*9 
15.6 
6.85 
{t 
15*9 
is-’8 
7* 1 
6.8 
6 - 95 
6 . 55 
6 *3 
15*9 
6.7 
6 . 55 
6.8 
16. o 
I 5 - 9 
16. o 
6.4 
6 - 75 
i 5 - 7 
15.6 
15*9 
15.8 
15-9 
16. o 
16. o 
While none of these needles yielded as high results as the standard, the 
one showing the highest values was tested on a sample of material having 
a penetration of 95 with the standard needle. A penetration of 103 was 
obtained. This eliminated the 0.042-inch drill rod from further consider- 
tion, since it was evident that a taper which would check with the standard 
needle on softer materials would give higher results than the standard on 
harder materials. 
Drill rod with a diameter of 0.041 inch was then tried. This actually 
measured 0.0405 inch, and the finished and polished needle from it had a 
diameter of 0.040 inch. Three pieces of that diameter were given tapers 
of -fey and inch, respectively, then polished and tested in com¬ 
parison with the standard needle. The results on four samples of 
bituminous materials are given in Table II. 
