Improvements relating to the Turning of Angular Sections on Lathes.
Year: 1891

page_text: Date of Application, 7th Jan., 1891-Accepted, 7th Mar., 1891
Improvements relating to the Turning of Angular Sections on
Lathes.
We, CARL GEORG DAHLGREN, Mechanic, and JOHN HUGO SVENSSON,
Engineer, both of Göteborg, in the Kingdom of Sweden, 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:
The object of this invention is to enable prismatic or angular sections to be
turned in a lathe by means of simple mechanism.
According to this invention, both the piece to be turned to the shape required
(hereinafter called the blank) and also the cutting tool are rotated simultaneously
with different ratio of velocities according to the shape of section to be given to the
piece when turned.
0
=
By this means sections having regular forms may be turned, said forms having
(when the radius of the cutting tool is equal to the greatest radius of the object
turned) a number of angles dependent on the velocities according to the
formula N=C where N
the number of angles, C the number of blades on the
circumference of the cutting tool, the rotary velocity of the tool and the rotary
velocity of the blank. Thus, a cutter having two equidistant blades, will, if driven
with a velocity double that of the blank cut out a four angled figure of section, the
faces of which are slightly convex; if driven with a velocity treble that of the
blank, it will cut out a hexagonal figure the faces of which will be slightly concave.
In the accompanying drawing
Fig. 1 is a plan view of a lathe fitted with the improvements.
Fig. 2 is a diagramatic section showing the turning of a four angled figure.
Fig. 3 is a similar view showing the turning of a hexagonal section.
In the drawings A. is the blank which is fixed on the live spindle e in the usual
manner, the live spindle e drives the shaft 2 by means of tooth wheels 23. On the
shaft is the toothed wheel 2 which gears with the spherical toothed wheel
through which passes the shaft d revolving therewith but connected to revolve with
the wheel by means of a long feather d' thereon moving in a key way in the wheel
so that it is freely movable back and forth through said wheel. The shaft d is
connected by an universal joint to the shaft a carrying the cutting tool B, said
shaft a being journalled parallel to the blank in a rest block with usual adjustments
parallel to and perpendicular to the blank.
By replacing the one or other pair of wheels 122 or 3 by similar gearing
wheels of different relative sizes, the proportion between the velocities of the
spindle e and shaft d, therefore between the blank and the cutting tool may be
altered at will.
2
.2°
In cutting out a four angled section the blade of the tool B meets the surface of
the blank at the point and moving in the direction of the arrow will have reached
the point travelling through the angle while the blank has moved through the
angle being one half of a bringing the point to the position y', a portion between y
and will therefore be cut away, to a maximum depth in the centre equivalent to
the greatest distance of overlap of the two circles; the arc y should be equivalent
to a quarter of the circumference of the blank therefore the distance y y¹ through
which the circles overlap subtends an angle of 60° or two-thirds of a right angle.
The velocities being as 2 to 1 the other cutting blade 2 of the tool will reach the
point y exactly as the point z (where the former cut ended) arrives at said point y,
the cut zy will then be made by the blade 62, similarly the cut y2 y3 is made by

page_text: the blade b¹ and the cut y³ y by the blade 62 thus completing the figure. The
numerals I to VII and 1 to 7 illustrate relative simultaneous positions.
To cut a hexagonal figure the velocity of the tool is to that of the blank as 3 to 1
the tool therefore passes through the angle v while the blank revolves through the
angle -the arc t u will subtend the sum of these angles and (the figure being six
sided) this sum will therefore be 60° and the angle o will thus be 45°.
อ
The tool revolves through a distance of half its circumference while the blank
moves through a sixth only, therefore the blade will meet the point u at the
position t and will cut the part u u', similarly the blade will cut u¹ u' and
again uu and the blade will cut u² u³ and u' t.
Similarly by use of different proportions of velocities and equivalent adjustment
of the angle subtending the overlapping part of the two circles, other figures may
be cut out.
It will be understood that by approaching the tool to the blank so that the angle
aforesaid is greater than its true proportion the figure will simply be cut to a
smaller scale while by setting the tool at a greater distance from the blank the part
necessary to complete a face of the figure will not be all removed but a less portion
will be removed the effect being to leave a portion of the original circular circum-
ference between each cut.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1. The combination of a lathe adapted to receive and revolve a blank, with a
rotary cutting tool adapted to be revolved with a velocity the proportion of which
to that of the blank is equal to the number of facets to be cut by said tool divided
by the number of blades thereon for the purpose described.
2. The combination of a lathe adapted to receive and revolve a blank with a
rotary cutting tool having two equidistant cutting blades and adapted to be
revolved with a velocity the proportion of which to that of the blank is equal to
half the number of facets to be cut by said tool for the purpose described.
3. The combination of the live spindle e adapted to receive and revolve a blank,
gear shaft, spur-wheel thereon, spherical wheel gearing with said
wheel, shaft d keyed to said wheel and movable back and forth therein,
universal joint e and shaft a with rotary cutting tool B said tool having equidistant
blades and adjustable rest block b carrying said shaft a, the whole substantially as
and for the purpose set forth.
Dated thin 7th 1
LT1001
HERBERT & Co.,
18, Buckingham Street, Strand, London, W.C., Agents for the Applicants.