Improved Machine for Grinding Spiral or Twist Drills.
Year: 1898

page_text: Date of Application, 5th Oct., 1898-Accepted, 5th Oct., 1899-
COMPLETE SPECIFICATION.
Improved Machine for Grinding Spiral or Twist Drills.
I, HUGO LUDWIG HERMSDORF, Proprietor of the Firm of Louis Hermsdorf, of
Rochlitzer Strasse, Chemnitz, Kingdom of Saxony, Empire of Germany, Merchant
and Manufacturer, 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 present invention relates to mechanism for correctly grinding the ends of
twist or spiral drills.
The object of the invention is attained by eccentrically mounting the drill
holder, which rotates on its vertical spindle, as also by the adjustment of a lever
on a segment, by which means the degree of "backing off" of the cutting edges
of the drill may be determined, in order to correspond with the diameter of the
drill being ground.
In order to render the said invention more easily intelligible, reference is had
to the accompanying drawings, in which similar letters of reference denote similar
parts throughout the several views:
Fig. 1 is a side elevation, partly in section, and
Fig. 2 a plan of the same.
The drill holder 6 and the segment c are fast on the spindle a, the latter rotates
in the eccentric sleeve d, which has a lever arm e fixed to it. The sleeve d
rotates in the bearing f so that the drill holder and the spindle a on turning,
will describe a curve. To the upper end of a spindle g is keyed a curved lever
arm h, a lever i being also fast on the lower end of said spindle. A curved lever
arm k is pivoted at I to the lever arm e and is formed to pass underneath (Fig. 1)
and over the lever h, being adjustably pivoted to this lever by means of the pin
in any one of the holes therein. Another similar curved lever m, pivotally
connected at II to the lever i, passes under and over the segment c, and may be
adjustably pivoted thereto by means of the pin in any one of the holes therein,
the pivots being varied according to the degree of "backing off" required.
The bearing f is provided with one or two guide bolts n, n¹ adapted to slide in
the machine frame o, so that the drill holder may be adjusted against the emery
wheel p, as the latter wears away. The emery wheel is fast on the shaft
which may be rotated by means of a cord passing round the pulley r and the guide
pulleys, or by any suitable device from any suitable source of power.
The shaft q may be raised in its bearings in o by means of a pivot hand lever s,
having a thumb lever s¹ underlying the lower end of said shaft q. A spring
serves to normally hold the shaft in its lowest position. This device provides for
the vertical adjustment of the emery wheel.
The device is manipulated in the following manner:
The drill is secured in the drill holder b in the usual manner, and the lever m
is adjusted to the segment c in the required manner, by means of the pin l, the
leverk being then connected to the lever h by the pin . Both these levers being
so adjusted as to give the required "backing off.'
If now the emery wheel p is rotated and the drill holder turned on its vertical

page_text: spindle, the drill secured to the holder will, by reason of the movement of the
eccentric sleeve d, describe a curve in a horizontal plane and being simultaneously
pressed against the emery wheel, the required "backing off" will be ground on
the end of the said drill.
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:-
Apparatus for grinding spiral or twist drills, characterized by a drill holder
mounted in a rotatable eccentric bearing and means for adjustably connecting
the said drill holder with the said bearing, so that the movement of the holder
causes a movement of the bearing, causing the drill to describe such a curve
against the grinding wheel, as to produce the required "backing off". on the end
of the drill, substantially as described.
בד
1000
AMBROSE MYALL,
2, Lancaster Place, London, W.C., Agent for the Applicant.