IMPROVEMENTS " SMANDARD SUBRAC PLATING
Year: 1874

page_text: LETTERS PATENT to Sir Joseph Whitworth, of Manchester, in the
County of Lancaster, Baronet, for the Invention of "IMPROVEMENTS
"
SMANDARD SUBRAC PLATING
ал
PROVISIONAL SPECIFICATION left by the said Sir Joseph Whitworth
at the Office of the Commissioners of Patents, with his Petition,
on the 7th September 1874.
I, Sir JOSEPH WHITWORTH, of Manchester, in the County of Lan-
caster, Baronet, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE MANUFACTURE OF STANDARD SURFACE PLATES," to be as
follows:-
-
This Invention has for its object improvements in the manufacture of
plane surface plates.
The efficiency of machinery largely depends on the truth of plane
surfaces. It is therefore of great importance to elliminate as far an
possible any causes which tend to render the standard itself incorrect.
Standard surface plates, even although strengthened by being cast with
deep stiffening ribs at the back, as they have been manfactured by.me

page_text: for many years past, are strained when lifted and suspended for use in
an inverted position to a degree which may produce sensible error.
In order to obviate this difficulty I construct improved standard
surface plates in the following manner:-I stiffen the surface plate at
the back by casting it with concentric circular ribs, which are crossed
with radial ribs at suitable intervals. In connection with the outer
circular rib I cast three bosses so arranged as to form an equilateral
triangle. These bosses are bored and tapped to receive screws, and. the
plate is fixed on the bed of the planing machine in which it is planed
by screws which enter the bosses, true surfaces being previously formed
at the parts in contact. When the plate is removed from the planing
machine three projecting pieces are inserted in the holes made in the
bosses, which serve either as supports or as means of connection for a
central handle or holder by which the plate is suspended when it is
required to be used in an inverted position. Thus the weight of the
plate during the process of manufacture, and while afterwards at rest,
and while in the use of the plate, whether standing on its supports or
suspended, is always supported at the same three points.
I find that my improved standard surfaces may be advantageously
made of a polygonal form, such that the metal of the plate is evenly
distributed round a central point which is equidistant from the three
points of support of the plate.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Sir Joseph Whitworth in the Great Seal Patent
Office on the 6th March 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, Sir
JOSEPH WHITWORTH, of Manchester, in the County of Lancaster,
Baronet, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Seventh day of September, in the year of.a
our Lord One thousand eight hundred and seventy-four, in the thirty-
eighth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Joseph Whitworth, Her special license.
that I, the said Joseph Whitworth, my executors, administrators, and
assigns, or such others as I, the said Joseph Whitworth, my executors,

page_text: .
administrators, and assigns, should at any time agree with, and no
others, from time to time and at all times thereafter during the term
thercin expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS
IN THE MANUFACTURE OF STANDARD SURFACE PLATES," upon the condition
(amongst others) that I, the said Joseph Whitworth, my executors
or administrators, by an instrument in writing under my, or their, or
one of their hands and seals, should particularly describe and ascertain
the nature of the said Invention, and in what manner the same was
to be performed, and cause the same to be filed in the Great Seal
Patent Office within six calendar months next and immediately after
the date of the said Letters Patent.
NOW KNOW YE, that I, the said Joseph Whitworth, do hereby
déclare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement thereof, that is to say :-
This Invention has for its object improvements in the manufacture of
plane surface plates.
The efficiency of machinery largely depends on the truth of plane
surfaces. It is therefore of great importance to eleminate as far as
possible any causes which tend to render the standard itself incorrect.
Standard surface plates, even although strengthened by being cast with
deep stiffening ribs at the back, as they have been manufactured by me
for many years past, are strained when lifted and suspended for use in
an inverted position to a degree which may produce sensible error.
In order to obviate this difficulty I construct improved standard
surface plates in the following manner: -I stiffen the surface plate at
the back by casting it with concentric circular ribs, or with a rib or ribs
surrounding and evenly distributed around the central point. In con-
nection with the rib or ribs I cast three bosses so arranged as to form an
equilateral triangle. These bosses are bored and tapped to receive.
screws, and the plate is fixed on the bed of the planing machine in
which it is planed by screws which enter the bosses, true surfaces being
previously formed at the parts in contact. When the plate is removed
from the planing machine three projecting pieces are inserted in-the-
holes made in the bosses, which serve either as supports or as means of

page_text: connection for a central handle or holder by which the plate is suspended
when it is required to be used in an inverted position. Thus the weight
of the plate during the process of manufacture and while afterwards at
rest, and while in the use of the plate, whether standing on its supports
or suspended, is always supported at the same three points.
I find that my improved standard surfaces may be advantageously
made of a polygonal form, such that the metal of the plate is evenly
distributed round a central point, which is equidistant from the three
points of support of the plate.
Figure 1 of the Drawings represents a plan, and Figure 2 a transverse
section of a hexagonal surface plate made in accordance with my
Invention. It has at the back two concentric circular flanges a, a; the
flanges are connected by bosses a¹, a¹. By means of these bosses,
which are most effectually supported by the ribs, the plate, whether in
process of construction or afterwards, in use or out of use, is always
supported. The bosses are tapped to receive screws 6, 6, the rounded
heads of which form the feet or supports on which the plate stands.
c is a piece having three radial arms and receiving the movable handle a
by which the plate is held when suspended. The arms are forked at the
ends, and embrace the necks of the screw feet b, b.
Figure 3 is a plan, and Figure 4 a transverse section of surface plate
made to the form of an equilateral triangle, which I find to be a con-
venient and suitable form; it admits of the ribs passing directly in a
stright line from one supporting boss to the other. a³, a², are radial
ribs to stiffen the central portion of the plate.
What I claim is the manufacture of standard surface plates, sub-
stantially as described.
In witness whereof, I, the said Sir Joseph Whitworth, have here-
unto set my hand and seal, this Sixth day of March, in the
year of our Lord One thousand eight hundred and seventy-five.