Year: 1896

page_text: A communication by ALBERT SCHMIDT, of 138 Friedrichstrasse, Berlin, in the
Empire of Germany, Engineer.
I, GEORGE CECIL DYMOND, M.I.M.E., of the Firm of W. P. Thompson
& Co., of 6 Lord Street, Liverpool, and 6, Bank Street, Manchester, both in the
County of Lancaster, 118, New Street, Birmingham in the County of Warwick
and 322 High Holborn in the County of Middlesex, Patent Agent, do hereby
declare the nature of this invention to be as follows:-
This invention has for its object a spiral or twist borer which is characterised by
its periphery being to a large extent reduced or recessed rearwardly so as to leave
or form a projecting ridge in proximity to the cutting edge on the periphery
throughout the course of the spiral thread or twist.
This projecting ridge has for its object, on the one hand, to produce an absolutely
cylindrical cutting of the borer and a better feeding of the lubricating material,
and, on the other hand, to afford a reliable support or guide for the borer in the
bore hole.
In the accompanying drawings, the object of the invention is shown in two
figures in elevation and plan respectively.
As may be seen from Figure 2, the periphery of the borer from a-b is recessed
or reduced backwards so that from b-c a ridge d is formed bordering on the
cutting edge e and running in the direction of the spiral thread or twist of the
borer, which ridge forms the outermost limit of the diameter of the bore.
Such a borer may, after the preliminary hardening, be ground mathematically
cylindrical with certainty because only the narrow ridge d is effected in the
cylindrical grinding, and thereby an absolutely cylindrical form of its outermost
parts can be imparted to the borer, so that the hole bored thereby is also
completely cylindrical and smooth, the borer fitting mathematically exactly into
the same.
The borer receives in this manner a double guidance, the first by means of the
point or front borer formed by the wellknown or ordinary projecting ridge f, and
secondly by the ridge d as soon as the outermost end of the outer cutter comes into
play as the ridge fits exactly into the bore hole.
This double guidance can, however, only be obtained with a borer such as shown
in Figures 1 and 2. If for instance the ordinary spiral borer known under the
name of the "Morse borer" be provided with such ridges the working would not
be the same as in the borer which forms the object of the present application,
because the guidance of the borer would only take place by means of the ridges d
and there would be no central guide existing as in the present case. Thus a
throwing out of the borer is inevitable because the ridge d at the commencement
of the boring begins to grate or scrape and would enlarge the bore hole. The
bore hole would thus, immediately from the commencement, receive a larger
diameter than the borer so that a dropping out or throwing out of the latter would
be inevitable.
This reducing or recessing of the face of the borer rearwards also affords to the

page_text: periphery the great alvantage that the lubricating material is better supplied to
the cutting surfaces and the borer is thereby more thoroughly cooled.
Deted this 21st day of Tul. 1806
A communication by ALBERT SCHMIDT, of 138, Friedrichstrasse, Berlin, in the
Empire of Germany, Engineer.
1, GEORGE CECIL DYMOND, M.I.M.E., of the Firm of W. P. Thompson
& Co., of 6, Lord Street, Liverpool and 6, Bank Street, Manchester, both in the
County of Lancaster, 118, New Street, Birmingham in the County of Warwick
and 322, High Holborn in the County of Middlesex, Patent Agent, 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 has for its object a spiral or twist borer which is characterised by
its periphery being to a large extent reduced or recessed rearwardly so as to leave
or form a projecting ridge in proximity to the cutting edge on the periphery
throughout the course of the spiral thread or twist.
This projecting ridge has for its object, on the one hand, to produce an absolutely
cylindrical cutting of the borer and a better feeding of the lubricating material,
and, on the other hand, to afford a reliable support or guide for the borer in the
bore hole.
In the drawings accompanying the Provisional Specification the object of the
invention is shown in two figures in elevation and plan respectively.
As may be seen from Figure 2, the periphery of the borer from a-b is recessed
or reduced backwards so that from b-e a ridge d is formed bordering on the
cutting edge e aud running in the direction of the spiral thread or twist of the
borer, which ridge forms the outermost limit of the diameter of the bore.
Such a borer may, after the preliminary hardening, be ground mathematically
cylindrical with certainty because only the narrow ridge d is effected in the
cylindrical grinding, and thereby an absolutely cylindrical form of its outermost
parts can be imparted to the borer, so that the hole bored thereby is also
completely cylindrical and smooth, the borer fitting mathematically exactly into
the same.
The borer receives in this manner a double guidance, the first by means of the
point or front borer formed by the wellknown or ordinary projecting ridge f, and
secondly by the ridge d as soon as the outermost end of the outer cutter comes into
play, as the ridge fits exactly into the bore hole.
This double guidance can, however, only be obtained with a borer such as shown
in Figures 1 and 2. If for instance the ordinary spiral borer known under the
name of the "Morse borer" be provided with such ridges the working would not
be the same as in the borer which forms the object of the present application,
because the guidance of the borer would only take place by means of the ridges d
and there would be no central guide existing as in the present case. Thus a
throwing out of the borer is inevitable because the ridge d at the commencement
of the boring begius to grate or scrupe and would enlarge the bore hole. The
bore hole would thus, immediately from the commencement, receive a larger

page_text: diameter than the borer so that a dropping out or throwing out of the latter would
be inevitable.
This reducing or recessing of the face of the borer rearwards also affords to the
periphery the great advantage that the lubricating material is better supplied to
the cutting surfaces and the borer is thereby more thoroughly cooled.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondent, I declare that what I claim is :-
An improved spiral or twist borer, characterised by its periphery being to a
large extent reduced or recessed rearwardly so as to leave or form a projecting
ridge in proximity to the cutting edge on the periphery throughout the course of
the spiral thread or twist, which ridge may easily be ground or sharpened
mathematically exactly cylindrical and affords the borer a reliable outer guide
or support so that the hole is bored exactly cylindrical and a better feeding of the
lubricating material is produced, substantially as herein before set forth.
Dated this 12th day of February 1897
WM. P. THOMPSON & Co.,
Agents.