Improvements in Keeping the Change Wheels of Screw Cutting Lathes Accurately in Gear, Applicable also to other Tools
Year: 1884

page_text: Improvements in Keeping the Change Wheels of Screw Cutting
Lathes Accurately in Gear, Applicable also to other Tools
I, THOMAS BUDWORTH SHARP of French Walls Smethwick in the county of
Stafford Mechanical Engineer do hereby declare the nature of my invention for
IMPROVEMENTS IN KEEPING THE CHANGE WHEELS OF SCREW CUTTING LATHES
ACCURATELY IN GEAR APPLICABLE ALSO TO OTHER TOOLS AND APPARATUS WHERE
CHANGE WHEELS ARE USED to be as follows:
In screw cutting lathes and other tools & apparatus where change wheels are
employed it is usual for the depth to which the said change wheels are put into
gear to be dependent on the care & judgement of the turner or other person
responsible for the proper working of them Now these points are not always
to be relied on and the teeth are frequently broken owing to the wheels gearing
together too deeply or not deeply enough or the wheels even if set to the proper
distance in gear to start with often getting altogether out of gear from various
causes when the work is spoilt in consequence
I therefor make what I hereby term "Centre-Bars" which are plain bars with
The holes at
eyeholes at the end and made preferably of malleable cast iron.
the end of these centre bars are of such a size that they can be accurately fitted
onto the same bolt, spindle pin or screw as the change wheels whose centres they
are intended to adjust, and of such a distance apart that they do adjust them
Further I stamp, engrave cast or otherwise mark on each of these bars a number
which number is equal to the total number of teeth in the two wheels whose
distance of centres it is intended to regulate.
Therefore when the turner or other person wishes to gear together two wheels
which possess say 70 and 30 teeth respectively he puts them roughly together and
having selected a bar with 100 marked on it he slips one eye over the same bolt
spindle pin or screw as one of the wheels and the other eye over the same bolt
spindle pin or screw as the other wheel and then having tightened all up he finds
the two wheels are exactly the proper distance in gear into one another (provided
of course the centre bars change wheels and other parts of the machine or
apparatus have been accurately and properly made in the first instance) he will
also find that no ordinary violence will alter them.

page_text: Of course the bar marked 100 will also do for any other two wheels whose teeth
together number 100, as 60 and 40, 75 and 25, 50 and 50 &c &c and a bar
marked 120 will do for 80 and 40, 70 and 50 &c &c and so on.
I may if I like have three or more holes on each centre bar with extra numbers
suitably placed or I may use adjustible eyes which by means of a screw or
otherwise can be brought nearer together or further apart but for all practicable
and reliable purposes I prefer the plain bar with only two holes and one figure
on it.
Dated-This seventh day of January: One thousand eight hundred and eighty
foun

page_text: I, THOMAS BUDWORTH SHARP of French Walls, Smethwick, in the county of
Stafford, Mechanical Engineer do hereby declare the nature of my invention for
IMPROVEMENTS IN KEEPING THE CHANGE WHEELS OF SCREW CUTTING LATHES
ACCURATELY IN GEAR, APPLICABLE ALSO TO OTHER TOOLS AND APPARATUS WHERE
CHANGE WHEELS ARE USED" and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following statement :-
In screw cutting lathes and other tools and apparatus where change wheels are
employed it is usual for the depth to which the said change wheels are put into
gear to be dependent on the care and judgement of the turner or other person
responsible for the proper working of them. Now these points are not always to
be relied on and the teeth are frequently broken owing to the wheels gearing
together too deeply or not deeply enough or, the wheels even if set to the proper
distance in gear to start with often getting altogether out of gear from various
causes when the work is spoilt in consequence.
I therefore make what I hereby term "Centre Bars" which are plain bars with
eye holes at the end and made preferably of malleable cast iron.
The holes at the end of these centre bars are of such a size that they can be
accurately fitted onto the same bolt, spindle pin or screw as the change wheels
whose centres they are intended to adjust and of such a distance apart that they
do adjust them. Further I stamp engrave cast or otherwise mark on each of these
bars a number which number is equal to the total number of teeth in the two
wheels whose distance of centres it is intended to regulate.
Therefore when the turner or other person wishes to gear together two wheels
which possess say 70 and 30 teeth respectively he puts them roughly together
and having selected a bar with 100 marked on it he slips one eye over the same
bolt spindle pin or screw as one of the wheels and the other eye over the same
bolt spindle pin or screw as the other wheel and then having tightened all up he
finds the two wheels are exactly the proper distance in gear into one another
(provided of course the centre bars, change wheels and other parts of the machine
or apparatus have been accurately and properly made in the first instance: he
will also find that no ordinary violence will alter them.
Of course the bar marked 100 will also do for any other two wheels whose teeth
together number 100. as 60 and 40, 75 and 25, 50 and 50 &c &c and a bar
marked 120 will do for 80 and 40, 70 and 50 &c and so on.
I may if I like have three or more holes on each "Centre Bar" with extra
numbers suitably placed or I may use adjustible eyes which by means of a screw
or otherwise can be brought nearer together or farther apart but for all practical
and reliable purposes I prefer the plain bar with only two holes and one figure
on it.
I will now proceed to explain with reference to the accompanying sheet of
drawings the manner in which my invention may be performed.
tf
Fig. I. represents a Centre bar that will do for any two wheels whose total
number of teeth together makes 100 and it will be observed 100 is consequently
marked upon it.
Fig. II. represents a similar bar but is marked 120 and it will be observed that
it is just one-fifth longer from centre to centre than the bar represented in Fig. I.
and will do for any two wheels whose total number of teeth is 120).
Fig. III. represents a skeleton view of the gearing at the end of a screw cutting
lathe with the two aforesaid centre bars in use, where A is the fixed spindle in the
fast headstock and has a wheel of 30 teeth on its axis: C is the fixed screw which

page_text: works the slide rest and has a wheel of 80 teeth on its axis and B is the movable
stud with two wheels of 70 and 40 teeth respectively on its axis and which have
hitherto been placed more or less properly in gear with the wheels A and C
respectively by the man in charge according to his care and judgement or want
of them.
.
Now these centre bars not only do not allow the wheels to gear into one another
otherwise than the correct depth but they also serve as a check against the
workman putting on a wrong wheel and generally speaking his often erroneous
actions are replaced by a simple and mechanically accurate appliance.
As however the precise details herein described and illustrated may be con-
siderably varied without departing from the nature of my invention I wish it to
be understood that I do not limit myself to the said precise details but can vary
them considerably according to the circumstances of the case and as my experience
dictates without exceeding the limits of my patent. For instance where I prefer
it I could use a plate or plates with a number of holes accurately drilled or bored
at the right distance apart and numbered accordingly.
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. The use of a link or plate, with or without adjustible eycholes, in addition
to or partially or wholly in place of the apparatus commonly employed for keeping
the centres of change wheels at their proper distance from one another substantially
as described and illustrated and for the purposes set forth.
2. The use of figures or designations on the links or plates described in this
specification which figures or designations clearly shew to what pair or series of
pairs of change wheels the said links or plates may be applied substantially as
described and illustrated and for the purposes set forth.
Wahnuary 1984