IMPROVEMENTS IN THE MANUFACTURE OR TREATMENT OF SCREW BOLTS AND OTHER SCREW-THREADED ARTICLES
Year: 1875

page_text: ETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn
Fields, in the County of Middlesex, Gentleman, for the Invention of
“IMPROVEMENTS IN THE MANUFACTURE OR TREATMENT OF SCREW BOLTS AND
OTHER SCREW-THREADED ARTICLES."-A communication from abroad
by François Joseph Barba, of Lorient, in the Republic of France,
Engineer.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson
at the Office of the Commissioners of Patents, with his Petition,
on the 1st October 1875.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County
of Middlesex, Gentleman, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN THE MANUFACTURE OR TREATMENT OF SCREW
BOLTS AND OTHER SCREW-THREADED ARTICLES," a communication to me from
abroad by François Joseph Barba, of Lorient, in the Republic of France,
Engineer, to be as follows:-

page_text: treatment of bolts, screws, or other screw-threaded articles or portions
which are exposed to violent shocks or strains, such for examplo as the
bolts used in securing the plates of armour-plated ships.
In ordinary bolts rupture generally takes place at the point of
smallest section, viz., at the "bottom of the groove formed by the screw
thread, and as rupture occurs before the fibres of the body or cylindrical
part of the bolt become loaded by an amount approaching the breaking
strain, the latter can never be extended or drawn out at the expense of
their elasticity, and the rupture takes place without any appreciable
extension.
According to this Invention the threaded portion is made of a metal,
such for example as wrought iron or steel, harder, or rendered harder
than the body of the bolt, so that such threaded portion shall be
rendered capable of greater resistance, and this result may be obtained
by various known processes in casting or forging.
According to one mode of carrying out this Invention it is proposed
to employ steel bolts produced by forging or rolling, and subsequently
tempered or hardened throughout a portion of their length corresponding
to the threaded part, the screw thread may however be cut either before
or after hardening.
The nut should likewise be manufactured of harder metal than the
body of the bolt, and it is proposed to construct it of hardened steel, or
it may be made of soft steel and subsequently tempered or hardened.
The hardening may be effected by dipping in oil, in water, or in a
saline solution, which is a sufficient good conductor of heat for the
quality of steel employed.
The depth of the threads should be calculated in proportion to the
difference in the tenacity of the metal employed in the manufacture of
the body or cylindrical part, and the threaded part of the bolt and the
height of the nut should likewise be calculated according to this depth
of the thread thus determined by the nature of the metal employed.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Henry Johnson in the Great Seal Patent
Office on the 30th March 1876.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middle-
sex, Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the First day of October, in the year
of our Lord One thousand eight hundred and seventy-five, in the
thirty-ninth year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said John Henry Johnson, Her
special license, that I, the said John Henry Johnson, my executors,
administrators, and assigns, or such others as I, the said John Henry
Jolinson, my executors, administrators, or assigns, should at any time
agree with, and no others, from time to time and at all times there-
after during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Inven-
tion for "IMPROVEMENTS IN THE MANUFACTURE OR TREATMENT OF SCREW BOLTS
AND OTHER SCREW-THREADED ARTICLES," a communication to me from abroad
by François Joseph Barba, of Lorient, in the Republic of France,
Engineer, upon the condition (amongst others) that I, the said John
Henry Johnson, by an instrument in writing under my hand and
seal, should particularly describe and ascertain the nature of the
said Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Seal Patent Office within six
calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that T, the said John Henry Johnson, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement, reference being had to the accompanying
Drawings and to. the letters and figures. marked thereon, that is to
say:
The said Invention relates to improvements in the manufacture or

page_text: The hardening may be effected by immersion in oil, in water, or in a
saline solution which is a sufficiently good conductor of heat for the
quality of steel employed.
It is obvious that the condition which theso bolts are required to
fulfill (i.c. that of the threaded part possessing greater power of
resistance than the cylindrical part), consequently determines the depth
of the thread or worm of the screw, the minimum section of which the
threaded part admits depending upon the excess of tenacity in the metal
used at that part. Assume for example a bolt of soft steel capable of
resisting a breaking strain of say about 28 tons per square inch, and
resisting about 34 tons per square inch when hardened. Let S represent
the sectional area of the body of the bolt, and s the minimum sectional
area of the threaded portion, the relative proportions should be S × 28
< 8 × 31 or < that is to say, the depth of the groove formed
by the threads of a bolt of soft steel about 3 inches diameter, for
example, should be sucli that the diameter at the bottom of the groove
would not exceed 2.8 inches.
S
8
34
28'
In the accompanying Sheet of Drawings Figures 1, 3, 5, 7, 9, 11, 13,
15, and 17.are sectional elevations, and Figures 2, 4, 6, 8, 10, 12, 14, 16,
and 18 are plan views respresenting a scries of bolts and nuts of different
diameters calculated for soft steels resisting in a natural stato a strain
of about 28 tons per square inch, and resisting about 34 tons per square
inch after hardening in cold water.
The depth of the threads should be calculated in proportion to the
difference in the tenacity of the metal employed in the manufacture of
the body or cylindrical part and of the threaded part of the bolt, and the
depth of the nut should likewise be calculated according to this depth
of the thread thus determined by the nature of the metal employed.
Having now described and particularly ascertained the nature of the
said Invention, and the manner in which the same is or may be used or
carried into effect, I would observe in conclusion that what I consider
to be novel and original, and therefore claim as the Invention sccured
to me by the herein-before in part recited Letters Patent is,―
First. Constructing the threaded portions of screw bolts, screws, and
other screw-threaded articles of a metal capable of greater resistance or
rendered capable of greater resistance than that of which the body or

page_text: cylindrical portion is composed, in order to render available the
elasticity of the latter, and prevent the ruptures which take place
without appreciable extension of the metal in bolts, and similar articles
subjected to sudden or violent shocks or strains substantially as herein-
before described.
Secondly. The application of a hardening process to the threaded
portion, and to the nuts of screw bolts or other screw-threaded articles
manufactured of soft steel, the depth of the threads being arranged in
proportion to the relative tenacity of the threaded portion, and of the
cylindrical portion or body of the bolt or other article, substantially as
herein-before described.
In witness whereof, I, the said John Henry Johnson, have to this
my Specification set my hand and seal, this Thirtieth day
of March, in the year of our Lord One thousand eight hundred
and seventy-six.