Improvements in Screw-cutting Lathes.
Year: 1892

page_text: Date of Application, 16th July, 1892-Accepted; 17th Sept., 1892
COMPLETE SPECIFICATION.
Improvements in Screw-cutting Lathes.
I, JOSEPH DAVIDSOHN of 7, Münz Strasse, Berlin, C., Germany, Dentist, 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:-
My invention relates to a screw-cutting lathe which by means of a simple
mechanisin, permits to produce threads of different pitch, and right-handed screws
as well as left-handed ones.
The mechanism by means of which this result is accomplished consists of a slide,
which is displaced transversally to the main-spindle, from which it derives its
movement, and is provided with an adjustable guide-bar effecting the lateral dis-
placement of the slide-rest carrying the tool according to the angular position said
guide-bar occupies in relation to the path of the slide.
It will be obvious that by altering the position of this guide-bar the lateral
displacement of the slide-rest will be increased or decreased, and that this lateral
displacement will be to the right or to the left according to the inclination of the
guide-bar. Thus it will be apparent that right-handed and left-handed screws of
different pitch may be cut on iny improved lathe.
My invention will be more readily understood by reference to the accompanying
drawings, in which :
Fig. 1 is a front elevation and Fig. 2 a plan of my improved screw-cutting lathe,
like letters denoting like parts in both views.
The main spindle a is rotated in any usual manner for instance by means of the
cone b and a double geared fast head, as shown. The right half of the spindle a is
supported in bushes y and the spindle is provided at its right end with the centre e
the face-plate c' and the catch-pin c², adapted to collide with the catch a fastened
to the blank. The latter is held between the centre c, already mentioned, and the
centre e provided on the loose head f Between the bushes the spindle a is
provided with a worm h. A worm-wheel i engages with the worm ; said worm-wheel
is fixed to a vertical axle j, on the lower end whereof there is mounted a sleeve j',
to which are secured the change-wheels i' and 2 (or more change-wheels if required).
The sleeve may be locked in relation to the axle by means of screws.
دلا
The part of the machine in which the axle jis journaled, may be displaced
laterally, so that by suitable displacement of said part and by a vertical displace-
ment of the sleeve either of the toothed wheels may be brought to engage
with the rack k, provided on the transverse slide 1. During the lateral displacement
of the axle the worm wheel i remains meshing with the worm, the length of the
latter being sufficient for securing this result. It is obvious that when rotating the
main spindle a, the worm h, worm wheel.i, and either of the change-wheels and i²
will effect a displacement of the slide 1, having the rack k, transversally to the
spindle a.
, said slide is pro-
In the middle of the
The latter may be
The slide is guided in the gauntry of the lathe, as shown at
vided at its ends with plates m, each of which has a slot m'.
slide 1, or nearly so, is located the pivot n for the guide-bar o.
secured in various positions by means of screws and nuts o' passing through the
slots m. One of the plates m, or both as shown, are graduated, and the guide-bar o
is provided with a corresponding sight and with a pointer o².
On the guide-bar glides the slide p, composed of two parts, the upper of which
may be turned in relation to the lower one; when adjusted, both parts may be
secured to each other by means of screws p³ sliding in suitable slots. To the upper

page_text: part of the slide p there is secured the boss pl, through which passes the guide-rod q;
the screw serves for locking the guide-rod and the boss p' in their relative
position.
q
At the right end of the guide-rod there is secured the slide-rests, carrying the
tool t, which is arranged in the usual manner. The slide rest s glides in a guide s¹.
The left end of the guide-rod q is guided in a bearing u.
The operation of my improved screw-cutting lathe is as follows:
First of all, the axle j is locked against lateral displacement in such a position,
that either of the wheels or meshes with the rack k. Similarly the guide-bar o
is secured by means of the screws o' and the upper and lower part of the slide p by
means of the screws p², and finally the guide-rod y is secured to the boss p¹ by means
of the screw 7. The lathe may then be set in motion by rotating the main
spindle a.
The worm h, meshing with the worm-wheel i, effects a rotation of the latter, of
the axle and the change-wheels and One of these wheels engages with the
rack on the slide 1, and thus causes the latter to be displaced transversally to the
main spindle a.
During this displacement the slide glides along the guide-bar o, and the slide-
rests which is connected to the said slide p by means of the guide-rod q is also
displaced laterally more or less according to the angle of inclination of the guide-
bar o, the displacement being effected from the right to the left, when the guide-
bar o is inclined to the left (as shown on the drawing), whereas the displacement is
effected in the opposite direction when the guide-bar o is inclined to the right.
If the ratio between the worm h, the worm-wheel i, the change-wheels
the rack
and
is known, it will be easy, by reading the number indicated on the scale by
the pointer o³, to calculate the displacement of the slide p during one rotation of
the main spindle a, that is to say, the pitch of the screw cut during this rotation.
It will be obvious that by altering the position of the guide-bar o the lateral dis-
placement of the slide p and consequently of the tool t will also be altered, so that
screw-threads of very different pitch may be cut by means of my improved
machine.
By the employment of change-wheels the limits within which these alterations of
the pitch may be made are extended considerably.
Besides the advantage of permitting the production of left-handed and right-
banded threads, as already mentioned, my improved screw-cutting lathe presents the
further advantage, that the tool, after having been brought back to its initial
position in order to cut the blank for a second time, passes exactly through the
thread produced at the first cut. This is of particular importance when cutting
screws of small pitch.
Having now particularly described the nature of my said invention, and in what
manner the same is to be performed, 1 declare that what I claim is :-
1. A screw-cutting lathe, comprising a slide-rest holding the tool, a slide con-
nected to the slide-rest, an adjustable guide-piece for effecting a lateral displacement
of the slide, another slide to which the guide-piece is secured, and means for effect-
ing a displacement of this second slide transversally to the main spindle, for the
purpose as described.
2. In a machine of the kind described: The combination, with the main spindle a
and the worm h, of the worm-wheel i, change-wheels, and slide 1, having rack k,
for the purpose as described.
3. In a machine of the kind described: The combination, with the main spindle a
and the worin h, of the worm-wheel i, secured to the axle j, the change-wheels,
secured to the sleeve j' displaceable on axle j, the bearings of said axle being dis-
placeable laterally, and of the slide 1, having rack k, substantially and for the
purpose as described.
4. In a machine of the kind described: The slide 1, having rack & and guide-
bar o, pivoted at n, and adjustable by means of screws o¹, gliding in slots m¹ of the

page_text: plates m, in combination with the slide p, the guide-rod g and the slide-rests,
holding the tool t, substantially and for the purpose as described.
5. In a machine of the kind described: The slide 1, having rack k and guide-
bar o, pivoted at n, and adjustable by means of screws o¹, gliding in slots m' of the
plates m, said guide-bar having a sight and a pointer o, in combination with the
slide the guide-rod q and the slide-rests, holding the tool t, substantially and for
the purpose as described.
Dated this 16th dar of July 1800
JOSEPH DAVIDSOHN,
By Geo. H. Rayner,
37, Chancery Lane, London, W.C., Agent for the Applicant.