Improvements in connection with the Grinding of Rotary Cutters.
Year: 1894

page_text: Date of Application, 23rd July, 1894
Complete Specification Left, 22nd Apr., 1895-Accepted, 23rd July, 1835
PROVISIONAL SPECIFICATION..
Improvements in connection with the Grinding of Rotary Cutters.
JOHN WILLIAM URQUHART 68 Cedar Road Leicester Engineer do hereby
declare the nature of this invention to be as follows:-
My invention relates to the grinding or sharpening of that class of rotary
cutters called involute and epicycloidal milling cutters. In order that a cutter of
this kind may be correctly ground or sharpened without the aid of a grinding
machine great care must be taken to gauge each tooth, and to grind an equal
amount off the face of each tooth. My invention of a grinding guide consists of a
series of parallel lines inscribed upon each tooth of the cutter. These lines are
parallel to the true cutting face of each tooth. My method of grinding by hand-
is then to grind each tooth not only until its face is parallel to a given line but to
grind every subsequent tooth until its cutting face is also parallel to the corre-
sponding line inscribed upon it. In this way the cutting face of each tooth is
maintained of the correct form and all the teeth of the same cutter will have their
cutting edges at a uniform distance from the centre of rotation.
Dated this 21st day of July 1894.
J. W. URQUHART.
Improvements in connection with the Grinding of Rotary Cutters.
JOHN WILLIAM URQUHART 68 Cedar Road, Leicester, Engineer, 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 the grinding or sharpening of that kind of rotary
cutters commonly called form mills, in which the shape of the teeth is preserved
during the process of sharpening by grinding away only the face of the teeth.
The milling cutters to which this description applies include those used for gear
cutting, twist drill and tap fluting, also those intended for shaping or moulding
edges or surfaces, whether the substance operated upon be composed of metal,
wood, leather, or the like.
In order that a rotary cutter of this kind may continue to act efficiently and
maintain the shape it was intended to produce it is necessary that, firstly, the
grinding or sharpening should preserve the cutting rake of the teeth, whether the
face of the teeth be intended to lie radial to the centre or at a more acute cutting
angle; and, secondly, that the teeth be ground square to the side or plane of the
cutter; and, thirdly, that every tooth should have an exactly equal amount ground
away in the sharpening process. In the operation of grinding such rotary cutters
without the aid of a dividing machine it is difficult if not impossible to preserve the
form and cutting qualities of the teeth, for if one or more of the latter be ground
away more than the others, the teeth that thus receive most grinding are thrown
out of the circle and do not cut at all.

page_text: In order to obviate this difficulty I have designed a system of guiding lines
(represented at a in the drawing) to be inscribed upon the teeth of the cutters
before mentioned. The lines consist of a series of parallels or, in some cases radi
Tuscribed upon the teeth and generally parallel to the true cutting faces of the
teeth. These lines are intended to lie close together and to be repeated
a curately that is to say, occupy the same relative position-upon every tooth of
the cutter. In the process of grinding, the operator has not only before him a line
exhibiting the true shape after the first face is ground away, but he has only to
treat each tooth until its face equally approximates to the corresponding line
inscribed upon it to ensure that every tooth of the cutter may perform its share of
'the work.
The guiding lines- may be inscribed upon the teeth in the following way =
A fixed arbor to receive the cutter is provided having its axis horizontal and
placed at a suitable height above a surface plate. There is also provided a stop,
to which each tooth of the cutter may be brought in turn. The inscribing may be
effected with an ordinary scribing block and point, the latter being provided with
an elevating and depressing screw adjustment, so that the point may be raised or
lowered by a space equal to that desired between the lines. If the lines are
intended to be radial from the centre of the cutter, the scribing point is made a
fixture in its block and the cutter itself is rotated the required distance separating
the lines. This latter movement is effected by means of a dividing plate.
Having now particularly described and ascertained the nature of my said inven-
tion and the manner in which the same is to be performed I declare that what I
claim is :
The use of a system of lines inscribed upon the teeth of rotary milling cutters
for the purpose already fully described.
Dated this 20th day of April 1895.