Year: 1888

page_text: Jate of Application, 2nd May, 1888
Complete Specification Left, 1st Mar., 1889
Complete Specification Accepted, 2nd May, 1889
BRYAN CORCORAN 31 Mark Lane, E.C. London Millstone Builder do hereby
declare the nature of this invention to be as follows:-
The Trammel consists of an upright spindle on which is fixed a straight edge at
right angle, a slide with quill sliding on the straight edge, a lower bearing for spindle,
an upper oscillating bearing to tighten, in adjusting gymbal held in frame bolted to a
fixed plate, loose chains suspended from the straight edge and an anxilary straight
edge adjustable for forming swallow.

page_text: a Millstone.
BRYAN CORCORAN 31 Mark Lane London Millstone Builder 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 an improved "trammel" to be used to ascertain
the inequalities in the surface of millstones with a view to their correction. At the
present time a straightedge or "staff" of wood is generally used for this purpose
it has a thin coating of colour given to it and it is then applied to the stone.
The object of the workman in applying the staff is to mark the high parts of the
stone, but great skill and care are required in producing a plane or true surface by
the indications of this instrument, as the staff will also colour the low sides of the
stone provided there is a hollow extending across the stone from side to side and
this difficulty is greatly increased when there is a large "swallow."
Now according to my invention instead of a staff resting on the surface of the
millstone I use a straightedge above the surface of the stone which can be made to
revolve from two fixed bearings in a true plane and by a suitable slide rest, any
or every part of the surface of the stone can be gauged to a corresponding true
plane parallel to this straightedge. I also have a shorter or auxiliary straightedge
which can be set at any angle with the other, so that the face of the stone can be
bevelled truly of an even gradient all round at any distance from the centre and
to any depth required for forming a "swallow" or depression.
.
In the drawings hereunto annexed is shown a trainmel constructed in the manner
I prefer for carrying out my invention.
Figure 1 is a side elevation of the trammel fixed ready for use: (The millstone
being shown in section.)
Figure 2 is a front elevation of the same.
Figure 3 is a front elevation and plan enlarged of the details of the straight edges
(shortened).
Figure 4a side elevation of details of bracket with gymbal and head bearing.
Figure 5 a front elevation of the same.
Figure 6 a plan of the same.
Figure 7 a front elevation of details of the slide rest.
Figure 8 a side elevation of the same.
The trammel fig. 1 and 2 consists of an upright spindle a turned at each end on
which is fixed near the lower end with suitable braces c. c. a straight edge b at right
angles with the spindle. A slide rest d resting on this straight edge can be made to
travel right across the whole or a portion of the face of the millstones, this slide holds
a quille at its lower edge and is furnished with a vertical adjustment f, the lower end
of the spindle rests and revolves in the cockhead bearing of the centre har g in the
runner millstone or any suitable bearing near the centre of the stone. The upper
,

page_text: bearing o is larger in diameter than the spindle besides being bell mouthed and it is
screwed into a tapering hole into the holder or inner ring of the gymbal / and being
split up at the upperside the lips so formed close concentrically as the bearing is
screwed further into the holder. This upper bearing of the spindle is held in a
gymbal h in a frame or bracket i furnished with a bolt u which firmly but easily
attaches it to the plate ; that is permanently fixed either to the side or bottom of any
beam & or other suitable holding. The whole is made preferably of metal but can be
of wood or other material and is provided with coarse and fine adjustments m.
The auxiliary straightedge n is pivoted on the back of the other straightedge and
can be adjusted to any angle and retained by the winged screw v.
Instead of the straightedge revolving with the spindle the trammel may revolve on
the spindle. The spindle in this case is fixed in the eye of the millstone and enveloped
in a sleeve furnished with perfect adjustments, and on this exterior spindle the
trammel fits and revolves. This dispenses with the independant top bearing but
I prefer the other arrangement described and shown in the drawings. In using my
arrangement the millstones is placed nearly level in any convenient place where the
upper bearing for the spindle can be suitably fixed over or nearly over the centre of
the stone. The spindle a is pushed up through the upper bearing o which can be
tilted in any direction for the purpose till the foot drops into the lower bearing t the
upper bearing o is then closed by turning the wings p until it holds the spindle
sufficiently firmly. The millstone is roughly adjusted to the trammel by being
packed, wedged or screwed up (my drawing represents the stone resting on a
trolley 9 provided with 3 screws w for this purpose). The millstone is in this way
roughly adjusted to the spindle with what I call my coarse adjustments which are
short linked chains / hanging from near each end of the straight edge b fig. 3 until a
corresponding number of links trail on the face of the stone at each side in whatever
direction the trammel is turned and as soon as this is done they are hooked up out of
the way. The slide d figs. 7 and 8 is then placed on the straightedge b fig. 2 and the
quille adjusted until it just touches the face of the stone. The three deepest valleys
or hollow places can be ascertained in this way and the trammel adjusted to them so
that the plane to be made can be attained to coincide with them if desired. The
perfect adjustment is obtained by my fine adjustment contained in the frame h around
the head bearing o which inclines the spindle in any direction desired by turning the
screws m.
The projections or high places on the face of the millstone are then successively
dressed until the whole of the face or any necessary part of it is in this perfectly
true plane parallel to that described by the straightedge when made to revolve and
this is indicated by the quill just touching the face in every part. To make a
"swallow" or inclined "bosom " the auxiliary straightedge n fig. 2 & 3 is set to
the desired inclination and the slide d is worked along it in the same way as it is used
on the main straight edge. A brush or piece of wood or other material may be
substituted for the quill and colour may be used to mark the stone. An ordinary
stone staff may conveniently be used with colour to mark the high places between two
spots that are previously ascertained by the trammel to be in the true plane.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be used, I declare that what I claim is
1. That the trummel has no bearing on the face of the stone.
2. That it is not necessary to fix the millstone level or perfectly true with my
instrument.
3. That the same adjustment answers for both the straightedges together.
4. That the slide rests by its own weight only and on the top of the straightedge.
5. That the slide not being held down ridgedly the quill cannot be jammed against
the face of the stone and cause any pressure against the adjustment of the trammel.
6. That the top bearing oscilates like a mariners compass to enable the top of the
spindle to enter easily at an angle and can also be afterwards tightened to it.
7. That my fine adjustment is capable of inclining the spindle in all directions.

page_text: 8. That my straightedge is not liable to get out of truth and require correcting to
a proof as is the case each time when a wooden stone-staff is used.
9. That there are no screws or nuts to be detached or small loose bits liable to be
mislaid.
10. That my trammel does not get in the way or prevent the workman dressing
any part of the face.
11. That my trammel enables a workman to dress a millstone as true as though it
were turned in :: lathe.
12. That my trammel can be adopted to a bedstone as well as a runner millstone.
Dated this 19th day of February 1889.
BRYAN CORCORAN.