Improvements in Chucks or Holders for Rotary Cutters.
Year: 1899

page_text: Date of Application, 4th Aug, 1899-Accepted, 9th Sept., 1899
COMPLETE SPECIFICATION.
Improvements in Chucks or Holders for Rotary Cutters.
I, MARSHALL, ROBINSON, of 3, Kingsley Road, Walthamstow, in the County of
Essex, Manager of Cabinet Factory, do hereby declare the nature of this inven-
tion 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 an improved holder for rotary cutters and especially
to the holders used for rotary dovetailing cutters for cabinet work.
Hitherto it has been usual to construct such holders with a central socket for
receiving the shank of the cutter with the result that the said cutter was only
capable of cutting dovetails of one size, furthermore if the cutter itself was not
very accurately constructed there was a liability of the dovetail slots not being
accurately cut.
The object of my invention is to so arrange the holder that the cutter may be
very accurately adjusted in the holder and may at the same time be adapted for
cutting dovetails of different sizes, and to this end it consists in providing a
holder or chuck one part of which carrying the cutter is eccentric to the other
part whilst the cutter is also mounted eccentrically in the part which directly
carries it.
To enable my invention to be fully understood I will describe the same by
reference to the accompanying drawing, in which:-
-
Figure 1 is a sectional elevation of my improved tool holder with the cutter
applied; and
Figure 2 is a plan view of the same.
Figures 3 and 4 are respectively an elevation and plan of the part of the tool
holder which directly carries the cutter; and
Figures and 6 are respectively an elevation and plan of the other part of
the tool holder.
a, are the two parts of the tool holder, the former of which (hereinafter
referred to as the head) is adapted to be applied in any suitable manner to the
end of the driving spindle and is provided with a hole c which is eccentric to
the axis of rotation of the said head, as clearly shewn by reference to Figure 6.
The other part of the holder (hereinafter referred to as the socket) has the end d
adapted to fit the eccentric hole c and is designed to be fixed therein by a screw e
Figure 1.
f is the cutter which is of ordinary construction, the said cutter having its
shank adapted to fit into the hole in the socket b, the said hole being
eccentric to the axis of the socket to the same extent that the hole e is eccen-
tric to the axis of the head a.
i is a screw for fixing the cutter in the socket b.
With this arrangement it will be understood that when the socket is so
fixed in the head a that the eccentricity of the hole h compensates for or is
opposite to the eccentricity of the hole c, the axis of the hole
will be in align-
ment with the axis of rotation of the head a so that the cutter will rotate truly
relatively with the head. If however, the socket be rotated for half a revolu

page_text: tion so that the eccentricity of the hole h is upon the same side of the axis of
the head a as the eccentricity of the hole c, then it will seem that the hole h
is in a position of greatest eccentricity relatively with the head a.
The advantage of this arrangement will be understood from the following
description: -Assume that the cutter f is adapted when running truly to cut
say a half inch dovetail and that the centre of the hole c is 16 of an inch from
the axis of rotation of the head a and the hole h 16 of an inch to one side of
the axis of the socket . If now the socket b is fixed so that the eccentricity
of the hole h is added to the eccentricity of the hole c the effect will be to move
the axis of the cutter 8 of an inch from the centre of rotation of the head a
with the result that the said cutter instead of cutting a half inch dovetail would
of the dovetail may be
cut a inch dovetail. It will be obvious that the size
adjusted as desired at any point between the two extremes by varying the posi-
tion of the socket b relatively with the head a.
It will be seen that it is necessary that both the hole in the socket b and the
hole in the head a be eccentric, were this not so it would be impossible to get
the cutter central relatively with the head, for example, if the hole h was central
with the socket b the cutter f could never be brought to the centre of the head a
by 16 of an inch.
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:-
1. A holder for rotary cutters comprising two parts eccentrically mounted rela-
tively with each other the hole in that part of the said holder which is adapted
to receive the cutter being also eccentric relatively with the socket, substantially
as, and for the purpose, described.
2. A holder for rotary cutters comprising a head adapted to be fixed to a
driving spindle, the said head having formed in it a hole eccentric to its axis of
rotation and a socket adapted to fit into the said hole and having a hole for carry-
ing the cutter eccentric to the portion which fits into the head, substantially as
described.
3. The manufacture and use of holders for rotary cutters, substantially as here-
inbefore described and illustrated in the accompanying drawing.
Dated the 4th day of August 1899
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.