Improvements in Boroug
Year: 1895

page_text: Date of Application, 29th Aug., 1895
Complete Specification Left, 4th Apr., 1896-Accepted, 30th May, 1896
Improvements in Boroug
I, ALFRED HERBERT of The Butts, in the City of Coventry in the County
of Warwick, Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention is applicable to screw-cutting lathes and capstan lathes, and
is intended to facilitate the cutting of screws.
In place of the leading screw usually employed I substitute a movable leading
screw (hereinafter called a leader), which may be of any desired pitch and which
is so arranged as to be readily changed. This leader is driven at any desired ratio
to the lathe spindle by means of change gearing, and I prefer to make this leader
of such a pitch that the number of threads per inch of the screw to be cut may be
divided by the number of threads per inch of the leader without remainder, so that
the nut gearing into the leader may be put into gear at any desired point with the
certainty that the screwcutting tool or chaser will always be in correct relation to
the screw which is being cut.
Further, I connect, by special means hereinafter described, the tool or chaser
with the nut which gears with the leader, so that the tool may be withdrawn from
its work at the same time and by the same movement as the nut is withdrawn from
the leader, and (conversely) so that the tool is returned to its previous position by
the same movement and at the same time as the nut is put into gear with the
leader.
The additional depth of cut for each successive traverse over the work is put on
by the handle which controls the cross slide screw.
The means adopted for connecting the tool and nut together are as follows:-
The screw which actuates the cross slide, instead of taking its end wise abutment
against the saddle itself, is fitted into and takes its end wise abutment against
a cylindrical sleeve which slides in a suitable hole bored in the saddle, so that when
this sleeve is moved inwards or outwards it moves the screw with it and consequently
also moves the cross slide to which the tool or chaser is clamped. This sleeve, by
means of a flange or projecting arm, is also attached to the nut or nut carrier, which
slides in a groove or way parallel with the sleeve, so that the nut moves in unison
with the sleeve and consequently in unison with the tool or chaser.
The sleeve is withdrawn and returned by an eccentric, cam, screw, or other
device.
Provision is made for readily changing the nut to suit the pitches of the various
leaders employed.
It will be seen from the above description that the cutting of a screw becomes a
simple and rapidly performed operation, thus when the tool has reached the end of
the screw being cut, a single movement of the eccentric or cam withdraws it, and
also the nut from the leader, so that the saddle can be run back to the starting
point and, the additional depth of cut having been put on by the cross screw, the
nut is returned into gear with the leader, and the tool to its correct position relative
to the screw being cut, without the need of reversing the lathe, and without the use
of stops or any calculation.
Deted this 28th day of A vơnst 1895.

page_text: Borow-cutting Dates.
I, ALFRED HERBERT of "Brantwood," Spencer Road, Coventry in the County
of Warwick, Engineer 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 to screw-cutting lathes and is particularly applicable to
capstan lathes where screw-threads are required to be cut more accurately and
more quickly than is possible with the ordinary chasing bar.
The invention will be best understood by reference to the accompanying drawings
in which
Figure 1 is a front elevation of portion of a lathe constructed according to this
invention.
Figure 2 is an elevation of the left-hand end of Figure 1 and
Figure 3 is a transverse vertical section on the line 3-3 of Figure 1.
Like letters indicate like parts throughout the drawings.
In place of the leading-screw usually employed for moving the saddle or
carriage A when screw-cutting, I preferably substitute a shaft B supported and
geared at the end adjacent to the fast or driving head C, in a similar manner to
such ordinary leading screw. The carriage A may be moved along the bed D by
hand in the ordinary manner by means of a rack D' fixed on the bed D and
a pinion E mounted on the carriage and operated by a hand wheel E' with or
without intermediate gearing.
On the shaft BI mount a hollow leading-screw or guide-screw F whose ends are
recessed or notched as at F¹ for engaging with one or more driving keys or
equivalent B¹ (shown in dotted lines in Figure 1) secured to the shaft B.
By notching both ends of the leading screw F, I am enabled to turn it end for end
in the event of one end becoming more worn than the other as might be the case,
if the lathe were used for producing a number of screws of shorter length than the
leading screw F. The end of the shaft B shown at the right hand side of Figure I
is supported in a sleeve G which is detachably secured in a bracket H rigidly
mounted on the lathe bed D. The inner end of the sleeve G abuts against the
hollow screw F and holds the latter in engagement with the key B¹. The
bracket H is split at H' and provided with a bolt H³ which, when tightened, clamps
the sleeve G in the bracket, so that the sleeve then acts as a fixed bearing; when
the bolt H2 is loosened the sleeve G may be withdrawn from the bracket H
and the leading screw F may also be moved end wise through the bracket and off
the shaft B, the hole through the bracket H being sufficiently large for this
purpose.
The device or, as it is herein termed, the "nut" for engaging with the screw F
consists of a bar J formed with a screw-threaded concave recess J' at each end;
this nut is securely bolted to a slide or carrier K, which, at its upper part carries
the cross-screw L by which the tool-slide M is moved towards and away from the
work in the lathe. The screw L instead of being supported in a bearing at each
end as ordinarily, is carried in one long bearing K (shown in dotted lines in
Figure 3) which is formed in one with the slide K, and guided in a hole bored in
the saddle A. The screw L engages with the tool-slide M in the usual manner, by
means of a nut M' as shown in dotted lines in Figure 3, and it is provided with
collars or equivalent L' to prevent it from moving end wise in the bearing K¹ and
with a handle L' by means of which it may be rotated.
In a bracket N rigidly secured on the saddle A is mounted a shaft O carrying
on one end a crank handle O' and on the other end a crank pin O' shown in dotted
lines in Figure 3. This crank pin engages with a hole or recess in a block O³

page_text: capable of sliding vertically in a guideway in the slide K and is adapted to be
moved through say about 180 degrees the arrangement being such that when the
crank-pin is at the innermost end of its stroke the tool-slide M is held adjacent to
the work and the nut Jis engaged with the leading screw F and when it is at the
outermost end of its stroke, the tool slide is away from the work and the nut J is
disengaged from the screw F, the engagement of the nut J with the screw F and
movement of the tool-rest towards the work being effected simultaneously,.
and vice versa, as regards the disengagement of the nut and screw and the outward:
movement of the tool-slide. A stop O in the slide K restricts the movement of the
block O to the necessary extent.
In the drawing I have shown the tool slide M provided with two adjustable
stops M and two tool holders M2; these are of ordinary construction and constitute
no part of my invention and only one of these stops and tool holders would be
necessary for screw-cutting. I have moreover shown an adjustable stop P for
limiting the movement of the carriage A and this also constitutes no necessary part.
of my invention, but may be used in combination with it.
The shaft B is connected with the lathe mandrel C¹ by change gearing B2 which,.
as in other screw-cutting lathes may be adjusted to suit the pitch of any particular
thread desired to be cut.
In order to ensure that the nut J may be engaged with the hollow screw F at.
any point without risk of cross-threading the work, the number of threads per inch.
of this screw F must divide without remainder into the number of threads per inch
of the screw to be cut, the particular screw F employed for cutting different threads.
being selected with this end in view.
To make this point clear let it be assumed that on an ordinary screw-cutting-
lathe whose leading-screw has four threads to the inch it is desired to cut a screw
with twenty-one threads to the inch; to attain this result it is necessary to arrange.
the gearing so that the work makes twenty-one revolutions to every four revolutions.
of the leading screw. If, under these conditions, the nut is disconnected from the
leading screw it cannot be again engaged with it and the tool be simultaneously
brought into proper operative position on the work until the latter and the leading
screw have rotated into certain definite positions in relation to each other. To
overcome this difficulty it has hitherto been customary to rotate the lathe
backwards while still retaining the nut in engagement with the leading screw, the
screw-cutting lathes for only this particular purpose being frequently provided
with reversing countershafts such an operation involves considerable waste-
of time.
Now supposing it is desired to cut a similar thread viz.;-twenty-one_threads.
per inch in a lathe constructed according to this invention, a leading screw F having
seven threads per inch is mounted on the shaft B and this latter is geared to the
lathe mandrel C¹ so that it will rotate once to every three revolutions of the work ;.
in consequence of this the nut J may be disengaged from and engaged with
the leading screw F with the absolute certainty that the tool will always come into.
correct operative position.
The operation of the before described apparatus is as follows:-
When the lathe spindle C' and shaft B are rotated the hollow leading screw F is.
also rotated and the carriage A will not be operated by the screw F so long as the
handle occupies its outermost position and the nut J is consequently not in.
engagement with the screw F. By turning the handle O¹ inwards the nut J is
moved into engagement with the screw F and simultaneously therewith the tool
(not shown in the drawings) is moved up to its work, the desired depth of "cut"
being adjusted by turning the handle L³. When the tool reaches the end of its
stroke or cut, the handle O¹ is turned outwards so as to simultaneously withdraw it
from the work and disengage the nut J from the screw F and thereby stop the
carriage. The carriage A is then returned to its starting position by turning the
hand-wheel E' the handle L' turned to give the necessary" cut," and the handle O¹
again turned inwards to cause the tool to be carried along the work as before.

page_text: I have hereiubefore described the "out" J as having a screw-threaded concave
recess Jat each end; this enables one "nut" to serve for engagement with two
screws F of different pitch as the threads of these two recesses would preferably be
made of different pitch. Although I prefer this arrangement, if only for the sake
of economy I may if desired form each "nut" J with only one screw-threaded
recess; besides this I may modify other parts of the apparatus without departing
from the spirit of the invention for example instead of the crank pin O³ I may
use an eccentric or other device for moving the screw-carrying slide K in the
carriage A.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, 1 declare that what I
claim is :-
1. In a screw-cutting lathe the combination with the carriage of a screw-carrying
slide such as K movable therein and a crank pin cam or equivalent for operating it
substantially as described and illustrated in the accompanying drawings.
2. In a screw-cutting lathe the combination with the carriage and leading screw
of a screw carrying slide such as K K¹ movable in the carriage and a nut such as J
secured to the slide and capable of being engaged with and disengaged from the
leading screw substantially as described and illustrated in the accompanying
drawings.
3. In a screw-cutting lathe a slide rest constructed and arranged substantially as
described and illustrated in the accompanying drawings.
4. The combination and arrangement of parts constituting a screw-cutting lathe
substantially as described and illustrated in the accompanying drawings.
Dated this 31st day of March 1896.
ALFRED HERBERT.
Boult & Wade,
Agents for the Applicant.