Treatment of the same to Increase their Strength.
Year: 1885

page_text: Treatment of the same to Increase their Strength.
I ALBERT HAMILTON EMERY of Stamford in the County of Fairfield and State
of Connecticut, United States of America, Civil Engineer, Vice President of the
Emery Scale Company, do hereby declare the nature of the said invention for
IMPROVEMENTS IN THREADED BOLTS, RODS AND PIPES; AND IN THE TREATMENT
OF THE SAME TO INCREASE THEIR STRENGTH, to be as follows:-
This invention relates especially to threaded rods, bolts and pipes which are
required to endure tensile or longitudinal strains, and to the treatment of such
threaded rods, bolts and pipes and to better adapt or qualify them to endure such
strains.
With threaded rods, bolts or pipes as ordinarily made, a defined line of weakness
exists at the termination of the thread in the body of the rod, bolt or pipe and
additional lines of weakness at the bottom of the screw threads, each inviting
fracture, under strain.
The object of the present invention is to remove the weakest point of the rod,
bolt or pipe from the screw thread and thus eliminate any such special point or
line of weakness as might invite fracture at any particular place.
To this end the invention consists in condensing the metal by cold compression
where the screw thread is formed and beyond the thread in the body of the rod,
the condensation running out gradually until the normal density of the metal is
reached in the untreated body of the rod, bolt or pipe.
By these means the limit of elasticity and tensile strength is largely increased in
the metal in those parts of the rod, bolt or pipe where from its shape or threading
special points of weakness would otherwise exist and any defined point or line
between the stronger and weaker metal is preferably avoided. It will be apparent
that if a rod bolt or pipe thus treated is subjected to a tensile strain in excess of
its elastic limit the point of minimum strength being not in or about the screw
thread or at any place where the conformation of the rod, bolt or pipe could
aggravate the weakness, nor on any particular line or plane, the effect of such
excessive strain, being distributed over the body, will tend to stretch and elongate
the whole body instead of causing the rod, bolt or pipe to part at a point of
special weakness. Hence it will be apparent that when a number of such rods,

page_text: bolts or pipes thus treated are employed as tension members in a truss or other
structure, any such tension members which may be subjected to an excessive load
by reason of inequality in length or strength or straining or from other causes,
will be adapted to elongate without violence or injury until the load is equalized
and distributed among all the tension members by which it should be sustained in
common.
In applying the invention to the construction or treatment of bars, links or bolts
which are formed at their ends with screw threads for coupling or connecting them
together or to other members of structures of which they are to form parts, or for
coupling or connecting any parts of structures where screw bolts or rods are used
for this purpose either with or without coupling sleeves or nuts; after the screw
threads have been produced by chasing or cutting or swaging in any of the known
modes, the threaded portion and the part adjacent thereto is placed between dies
formed to fit the screw thread and subjected to very heavy pressure while cold or
practically or nearly cold, the pressure being sufficient in degree and continued for
a sufficient time to impart a permanent set and condensation to the metal, and the
faces of the dies being so formed that the maximum condensing pressure extends
throughout the length of the screw thread and beyond this into the body of the
bar or bolt and gradually diminishes until it ceases altogether in the untreated
body of the bar or bolt without producing any special line or plane of demarkation
between the untreated and the treated or condensed metal which might invite
fracture under excessive strain.
In applying the invention to threaded pipes the same principle is carried into
effect preferably by the use of a mandrel formed with a slightly tapering end and
forced into the pipe end by hydraulic pressure or other means, while the pipe is
supported by three or more dies moving radially and forced inwardly upon the
pipe by hydraulic or other pressure, the faces of the dies being formed with
threads to fit those in the pipe and furthermore formed so as to slightly recede.at
their sides. or ends toward the body of the pipe in order that the condensing
pressure may gradually run out without any sharply defined limit, as and for the
purposes already described with reference to the treatment of threaded rods and
bolts according to this invention.
It will be manifest that although the metal is practically cold, and preferably
quite cold while under this treatment the condensing pressure cannot be applied
with due effect without having the surface of the pipe rod or bolt within the dies
encircled by the dies as completely as is practicable while permitting the slight
inward movement of the dies which is necessary in applying the pressure.
In order to avoid the formation of fins on the threaded pipe, rod, link or bolt,
the dies or one or more of them are repeatedly retracted and a slight turn
imparted to the pipe, rod or bolt to screw it in or out within the dies so as to
expose a new surface to the pressure when the dies are again brought down.
Movement may be imparted to the mandrel in the pipe end by other than
hydraulic pressure;-for example, by rack and pinion or screw, or levers, or other
suitable mechanical means; and the moving die or dies employed for treating the
threaded parts of either pipes, rods or bolts may be operated either by hydraulic
pressure, or by screw, lever or drop press.
C

page_text: Parvat, nous, and pos
Treatment of the same to Increase their Strength.
4
C
I. ALBERT HAMILTON EMERY of Stamford in the County of Fairfield and State
of Connecticut, United States of America, Civil Engineer, Vice President of the
Emery Scale Company, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:-
This invention relates especially to threaded rods, bolts and pipes which are
required to endure tensile or longitudinal strains, and to the treatment of such
threaded rods, bolts and pipes to better adapt or qualify them to endure such
strains.
With threaded rods, bolts or pipes as ordinarily made a defined line of weakness
exists at the termination of the thread in the body of the rod, bolt or pipe, and
additional lines of weakness at the bottom of the screw threads, each inviting
fracture, under strain.
The object of the present invention is to remove the weakest point of the rod,
bolt or pipe from the screw thread and thus eliminate any such special point or
line of weakness as might invite fracture at any particular place.
To this end the invention consists in condensing the metal by cold compression
where the screw thread is formed and beyond the thread in the body of the rod,
the condensation running out gradually until the normal density of the metal is
reached in the untreated body of the rod, bolt or pipe.
By these means the limit of elasticity and tensile strength are largely increased
in the metal in those parts of the rod, bolt or pipe where from its shape or
threading special points of weakness would otherwise exist, and any defined point
or line between the stronger and weaker metal is preferably avoided. It will be
apparent that if a rod, bolt or pipe thus treated be subjected to a tensile strain in
excess of its elastic limit the point of minimum strength being not in or about the
screw thread or at any place where the conformation of the rod, bolt or pipe
would aggravate the weakness, nor on any particular line or plane, the effect of
such excessive strain, being distributed over the body, will tend to stretch and
elongate the whole body instead of causing the rod, bolt or pipe to part at a point
of special weakness. Hence it will be apparent that when a number of such rods,
bolts or pipes thus treated are employed as tension members in a truss or other
structure, any such tension members which may be subjected to an excessive load
by reason of inequality in length or strength or straining, or from other causes,
will be adapted to elongate without violence or injury until the load is equalized
and distributed among all the tension members by which it should be sustained in
common.
In applying the invention to the construction or treatment of bars, links or bolts
which are formed at their ends with screw threads for coupling or connecting them
together or to other members of structures of which they are to form parts, or for

page_text: coupling or connecting any parts of structures where screw bolts or rods are used
for this purpose either with or without coupling sleeves or nuts; after the screw
threads have been produced by chasing or cutting or swaging in any of the known
modes, the threaded portion and the part adjacent thereto is placed between dies
formed to fit the screw thread and subjected to very heavy pressure while cold or
practically or nearly cold, the pressure being sufficient in degree and continued for
a sufficient time to impart a permanent set and condensation to the metal, and the
faces of the dies being so formed that the maximum condensing pressure extends
throughout the length of the screw thread and beyond this into the body of the
bar or bolt and gradually diminishes until it ceases altogether in the untreated
body of the bar or bolt without producing any special line or plane of demarkation
between the untreated and the treated or condensed metal which might invite
fracture under excessive strain.
In applying the invention to threaded pipes the same principle is carried into
effect preferably by the use of a mandrel formed with a slightly tapering end and
forced into the pipe end by bydraulic pressure or other means, while the pipe is
supported by three or more dies moving radially and forced inwardly upon the
pipe by hydraulic or other pressure, the faces of the dies being formed with threads
to fit those in the pipe and furthermore, formed so as to slightly recede at their
sides or ends toward the body of the pipe, in order that the condensing pressure
may gradually run out without any sharply defined limit, as and for the purposes
already described with reference to the treatment of threaded rods and bolts
according to this invention.
It will be manifest that although the metal is practically cold and preferably
quite cold while under this treatment, the condensing pressure cannot be applied
with due effect without having the surface of the pipe, rod or bolt within the
dies, encircled by the dies as completely as is practicable while permitting the
slight inward movement of the dies which is necessary in applying the pressure.
In order to avoid the formation of fins on the threaded pipe, rod, link or bolt,
the dies or one or more of them, are repeatedly retracted and a slight turn imparted
to the pipe, rod or bolt to screw it in or out within the dies so as to expose a new
surface to the pressure when the dies are again brought down.
Movement may be imparted to the mandrel in the pipe end by other than
hydraulic pressure; for example, by rack and pinion, or screw, or levers, or other
suitable mechanical means; and the moving die or dies employed for treating the
threaded parts of either pipes, rods or bolts may be operated either by hydraulic
pressure, or by screw, lever or drop press.
Machinery for carrying this invention into effect may be variously constructed
and its construction will be necessarily varied to suit the form and nature of the
object to be produced or treated.
In the accompanying drawings: Figure 1 is a longitudinal section of a set of
dies suitable for treating the threaded ends of screw rods, bars, links, bolts or the
like. Figure 2 is a side elevation, partly in section, showing the said dies and the
end of a screw rod or bolt undergoing compression between them: Figure 3 represents
a transverse section through the dies on the line 3, 3, Figure 1.
Figure 4 is a longitudinal section on the line 4, 4, figure 5 but partly in
elevation, showing dies and their accessories adapted for carrying out the invention
in its application to the condensation of the threaded ends of pipes.
Figure 5 is a transverse section of the same on the line 5, 5 figure 4.
Referring to Figures 1, 2 and 3: 1, 1, represent concave faced dies, any
desirable number of which may be employed, having cylindrical backs, converging
longitudinally and fitted to slide in corresponding converging cylindrical seats
within a sleeve or housing 3. The dies 1 are connected by a cruciform head 2 the,
arms of which engage in recesses near the heels of the dies, so as to compel
them to move in unison. The inner faces of the dies are screw threaded, as shown
in Figure 1 in order to produce the desired screw thread on the bar or bolt B in
the operation of condensing the metal by pressure applied while the said bar or

page_text: bolt is in a cold or moderately heated state, as already explained. The radial
pressure of the dies is produced by their longitudinal movement within their con-
verging sleeve or housing 3 which longitudinal movement may be imparted by a
ram or plunger 4 working in a cylinder 5 from which pipes 11, 12 connect with
Buitable pumps.
In order to produce the effect, hereinbefore explained, of imparting a maximum
tensile strength to the bar or rod throughout the length of its threaded portion
and beyond this into the body, and cause the tensile strength gradually to
diminish to a point where it becomes normal, the dies 1, by which the ends of the
bars, rods or bolts are condensed by compression while cold or in a slightly heated
state, are formed in their central portions with parallel faces from a to b for example
extending throughout the length of the screw thread and to a sufficient distance
beyond it to prevent the formation of a defined plane of possible fracture at the
point where the screw thread runs into the body of the bar. From 6 to c the faces
of the dies are inclined away from one another very slightly (and to an extent
which in practice may be imperceptible to the eye, but which in the drawings is
exaggerated for the purpose of illustration) so as to cause a gradual reduction in
the force of compression and the consequent condensation of the metal from the
point b to the main body of the bar, where the strength is normal; but it is
preferable to provide between points b and c a zone of pressure in the dies, which
without imparting any considerable condensation to the metal, will serve to clamp
the bar or bolt so as to prevent the outward or endwise flow of the metal under
the pressure of the dies.
In order to prevent the formation of fins on the threaded bar or bolt by the
action of the divided dies, the pressure of the dies is relaxed and the bar or bolt
turned partly on its axis two or three times during the operation.
If preferred, the screw threads may be partially formed by chasing or cutting
before the operation of compression between dies; or the cold compression. may be
performed by smooth faced dies, and the screw threads may be chased or cut in
the condensed metal at a subsequent operation. The radial motion of the dies in
compressing the metal is but slight; hence the invention may be effectually carried
out by partially forming the threads by chasing or by preliminary pressure between
dies while the metal is either hot or cold, and subsequently, when the metal is cold,
compressing it and finishing the threads by means of dies, as herein represented
and described, which, by reason of the slight radial motion of the dies required in
cold-compressing the metal and completing the threads, may be set very close
together, the space between them being insufficient to permit the radial flow of
metal and the consequent formation of projecting fins to any considerable extent.
In thus condensing the threaded ends the main portion of the bar, rod or bolt is
left in its original ductile state, so that it may bend and otherwise accommodate
itself to its position in service, while the threaded ends are strengthened so as to
obviate the danger of breaking through the threads.
If the threaded portion of the bar only were compressed, the termination of the
compressed and condensed portion at the end of the thread would make a defined'
point of fracture; hence the heavy pressure is extended beyond the threaded'
portion into the body of the bar, and gradually diminished till the untreated
portion of the body is reached. The result of this treatment is that when such a
bar is subjected to a strain the untreated portion having a lower limit of elasticity'
will be the first to yield, while the threaded portion and that immediately adjoining.
it will be relieved of injurious strain.
In the ordinary mode of producing screw-threads by rolling or swaging, any
such compression as there may be abruptly terminating with the screw thread, it
is manifest that a weak line is produced at the junction of the screw thread and
the body of the rod or bolt; and it is also true that in the threaded portion of the
5 bar or bolt the production of screw-threads by swaging or rolling, as now practiced,
even if this should be done in cold metal; does not produce an effective compression
and condensation of the metal throughout the entire body, as in the improved

page_text: mode of cold compressing and condensing in dies of suitable form, as hereinbefore
described.
In Figures 4 and 5 three converging dies are shown mounted radially in a
suitable housing 3, and having a slight motion imparted by hydraulic rams 4,
working in cylinders 5.
The faces of the dies are screw threaded as shown in order to produce the
desired screw thread on the pipe P, and are so formed that in compressing the
pipe a maximum condensation may be imparted to the metal throughout the
length of the screw-thread and beyond to a sufficient extent to avoid the formation
of any defined line or plane of fracture. To this end the faces of the dies from a
to b are made parallel, while from b to c they diverge slightly, to an extent which
in practice may be imperceptible to the eye, but in the drawings is exaggerated for
the purpose of illustration, the object of this divergence being to cause the con-
densation of the metal to gradually decrease from the point b until the normal
tensile strength is reached in that portion of the pipe which has not been treated.
In order to impart this permanent condensation to the metal, the pipe must be in a
cold state, or practically so. It is preferably cold; but if heated at all this must not
be to a sufficient extent to impart free ductility to the metal or cause it to flow easily
under the pressure of the dies, as in the ordinary process of forging or hot swaging.
To enable it to resist the pressure which is imparted to condense the metal, and
preferably to form the thread at the same operation, the pipe P is supported
within by a mandrel 6, having a slightly tapering end, the said mandrel being
operated by a ram or plunger 7 within a hydraulic cylinder 8. The forcing pipes 9
of the several ram-cylinders 5 may be connected with a common pump and the
retracting pipes 10 with another pump. 11 represents the forcing pipe, and 12 the
retracting-pipe of the mandrel-ram 7, 8. The invention may be carried out by
the use of this or analogous apparatus in various ways. For example, the
mandrel 6 may first be forced into the pipe, completely filling the same, while
the dies 1 are retracted, the said dies being then forced down to condense the
metal and form the screw thread. The dies are then retracted and the pressure
repeated once or twice, the pipe being partly turned at each operation in order to
prevent the formation of fins or irregularities in the thread. Or the dies may be
pressed upon the pipe while the mandrel is withdrawn and the pipe unsupported
on the inside, the tapering mandrel being subsequently forced in by the action of
the hydraulic press 7, 8, so as to expand the pipe within the dies, completing the
formation of the thread and the desired condensation of the metal. Or fixed dies
may be used, threaded on the interior, as already described with reference to the
moving dies, the pipe being inserted between the said fixed dies and expanded into
threads by the tapering mandrel 6, so as to condense the metal and thread the
pipe end at the same operation. Afterward the mandrel is withdrawn and the
pipe screwed out. Or the thread may be partially formed on the pipe by the
customary cutting or chasing operation, and may be completed by the compression
dies and mandrel in any of the modes already described. Or the pipe end may be
condensed between smooth faced dies, and the threads subsequently cut in the
condensed portion.
Movement may be imparted to the mandrel by other power than by a hydraulic
press for example by a rack and pinion, screw, or levers, or other well known
equivalent mechanical means.
The dies 1 may, if preferred, be operated by lever, screw or drop, instead of by
hydraulic pressure. If only the threaded portion of the pipe were compressed, the
termination of the compressed and condensed portion at the end of the thread
would make a defined point of fracture; hence the heavy pressure is extended
beyond the threaded portion into the body of the pipe, and gradually diminished
till the untreated portion of the body is reached. The result of this treatment is
that when such a pipe is subjected to a strain the untreated portion, having a
lower limit of elasticity, will be the first to yield, while the threaded portion and
that immediately adjoining it will be relieved of injurious strain.

page_text: It will be understood that the invention may be carried into effect in a great
variety of ways, the above serving as illustrations of suitable apparatus for the
purpose. In each case the local cold compression and consequent condensation of
the metal serve to impart increased tensile strength thereto at and near the screw
threaded portion, while the untreated body of the bar, bolt or pipe may be left in
its original condition as to strength and ductility.
By the terms "cold" and "nearly or practically cold" used as descriptive of the
condition of the iron under treatment, it is meant that the metal should be cold
and must not be heated to a sufficient degree to impart free ductility or permit it
to flow easily under pressure, as in the ordinary processes of forging and swaging.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:
1. The mode or process of increasing the strength of screw rods, bars, bolts or.
pipes the same consisting in compressing the metal while cold, or nearly so, so as
to condense it to a maximum extent throughout the length of the screw thread
and beyond this into the body of the bar or rod, and thence in a gradually reduced
degree to a point where the normal tensile strength is reached in the untreated
portion or body of the bar bolt, or pipe.
2. A rod, bar, link, bolt, pipe or tube having threaded ends condensed by the
compression of the metal while in a cold or moderately heated state, the said
condensation extending throughout and beyond the length of the threaded portion,
and gradually decreasing to a point where the normal density and tensile strength
of the metal in the untreated body or main portion of the pipe bolt or other object
are reached.
3. The treatment of threaded bolts rods and pipes by the aid of apparatus.
substantially as herein set forth.