Mar. 13,1916 
New Penetration Needle 
1125 
About the time this work was completed, a second standard needle 
was obtained from the same source as the one used in the foregoing tests. 
In order to determine the accuracy with which a number of the new 
type of needle could be readily made, seven were prepared and checked 
against both the old and new standard on two distinct types of bitumi¬ 
nous material. The results are given in Table IV. Each result is an 
average of at least three determinations. 
Table IV .—Results of a comparative test of new and old standard penetration needles 
and seven others of the new type 
Needle. 
Sample 
No. 8957 
(Gilsonite 
blown oil 
asphalt). 
Sample 
No. 8962 
(California 
asphalt). 
Needle. 
Sample 
No. 89^7 
(Gilsonite 
blown oil 
asphalt). 
Sample 
No. 8962 
(California 
asphalt). 
New standard.... 
94 
96 
Needle No. 4. 
92 
96 
Old standard. 
01 
06 
Needle No. 5 . 
01 
06 
Needle No. 1. 
y 
80 
y 
Q A 
Needle No. 6. 
y 
01 
y 
q6 
Needle No. 2. 
y 
90 
y*r 
97 
Needle No. 7. 
y 
90 
y 
95 
Needle No. 3. 
91 
95 
It will be noted from the above that all seven new needles check very 
closely with the old standard needle on both samples, and that on sample 
8957 they check closer with the old standard than do the two standards 
with one another. The lack of uniformity in the shape of the two stand¬ 
ard needles, the uniformity of the new type of needle, and the relative 
shapes of the old and new forms of needle are shown in Plate LXXXIII, 
figure 2, which is a reproduction of an enlarged photograph of the two 
standard and seven new needles referred to in Table IV. 
The following conclusions are offered as a result of the above investi¬ 
gation : 
(1) That the No. 2 sewing needle which has heretofore been used for 
the penetration test can not be taken indiscriminately, but must be care¬ 
fully selected and standardized. 
(2) That there is no recognized established standard with which new 
needles can be compared, and that it is not feasible to accurately de¬ 
scribe the dimensions of a parabola needle. 
(3) That the so-called standard needles furnished with penetration 
machines may vary among themselves. 
(4) That the writers have designed a needle which gives results in close 
accord with existing standards and has, moreover, the advantage of being 
accurately described and easily reproduced. 
(5) The needle is made by placing a 2-inch length of 0.041-inch an- 
nealed-steel drill rod in the chuck of a high-speed lathe, and by means of 
a fine sharp file turning the end to a sharp point having a % -inch taper. 
When it has been made as smooth and sharp as possible by this means, 
