Safety lathe dog

A statically balanced safety lathe dog for use with lathes of the type normally found in the average machine shop and which is characterized by the eccentricity of its mounting on the work to be turned whereby to effect a camming action in operation on the lathe and thereby act to push an operator's hand away from a danger area by a wiping action because of the sliding contact created by the camming feature of the dog rather than by the striking action of the typical or usual lathe dog.

BACKGROUND OF THE INVENTION 
Heretofore the typical lathe dog included an opening for mounting on a 
workpiece and one or more set screws for securing the dog to the work. The 
mounting opening usually was centrally located and a projecting tailpiece, 
which in the typical lathe dog was bent at a right angle to the body 
portion of the dog for cooperation with a radially slotted face plate on 
the lathe, completes the conventional arrangement as generally utilized in 
the average machine shop. Some lathe dogs have included certain safety 
features but these have comprised nothing more than a smooth outer surface 
and avoiding any projecting elements such as by recessing the set screws 
for securing the lathe dog to the work which might otherwise catch an 
operator's clothing, or cut a hand or an arm. The present invention not 
only avoids such dangerous projections and provides a smooth outer surface 
but shapes the lathe dog and mounts it on the workpiece in such a manner 
that an operator's hand or arm coming in contact with the safety lathe dog 
is pushed out of danger by a rotary sliding action obtained by the camming 
effect of the eccentrically mounted dog member. 
OBJECTS OF THE INVENTION 
The primary object of the invention is to provide a statically balanced 
safety lathe dog adapted to push an operator's hand or arm out of the path 
of possible danger by a wiping action or sliding contact afforded by a 
rotary camming operation of the lathe dog eccentrically mounted on a 
workpiece. 
The principal object of the invention is obtained by the provision of a 
safety lathe dog having an off-center opening for receiving a workpiece 
with the lathe dog in generally the form of a disc or plate having smooth 
outer surfaces with recessed screws installed through the perimetrical 
surface to secure the lathe dog to the workpiece. 
Another object of the invention is the provision of a safety lathe dog in 
the form of a smooth surfaced disc or plate having an eccentrically 
disposed opening for the mounting of a workpiece and having removable 
insert members fitted in the eccentrically disposed opening and secured by 
set screws and each having a central opening of different size from that 
in any other insert whereby to receive the workpiece and adapt the safety 
lathe dog for use with workpieces of various sizes.

DESCRIPTION OF PREFERRED EMBODIMENT 
In the drawings 10 represents a disc-like plate member comprising the 
safety lathe dog of the invention and which is provided with an opening 11 
extending therethrough. The opening 11 is disposed substantially to one 
side of the center of the disc-like dog member so that it is eccentrically 
located in the dog member. An undercut groove 12 extends entirely around 
the opening 11 adjacent one surface of the plate-like disc member 10 to 
provide an annular recess at this point. Diametrically opposed tapped 
openings 13 and 14 extend through the plate member 10 from the perimeter 
15 to the inner circumferential wall 16 of the opening 11 for the 
reception of Allen type set screws 17 which in the applied position are 
recessed below the surface of the perimeter so that they do not project 
beyond the perimeter. A hole 18 is provided through plate member 10 
extending radially inwardly from the perimeter 15 to the circumferential 
inner wall surface 16 of the opening 11 and is located at the point where 
the opening 11 is most closely adjacent to the perimeter 15. The hole 18 
receives an Allen type set screw 19 which passes therethrough and is also 
recessed below the surface of perimeter 15 in the applied position to 
avoid projecting beyond the perimeter. A bushing 27 may be provided in the 
mounting 10 and is set in adjacent the innermost end of hole 18 through 
which the set screw 19 passes. 
The eccentrically located opening 11 is adapted to receive a removable 
insert member 20. The insert member closely fits the size of the opening 
11 with the outer circumferential face 21 thereof engaging the inner 
circumferential face 16 of the opening. An outwardly directed annular 
flange 22 adjacent one face of the insert member engages in the undercut 
groove 12 to position the insert in the dog member 10 with both faces of 
the insert member substantially flush with the respective faces of the 
lathe dog member. Diametrically opposite detents 23 are provided on the 
surface of the annular face 21. These detents are engaged by the set 
screws 17 to fasten the insert in the lathe dog member and fix the insert 
against relative rotation or displacement. The insert member 20 is 
provided with a radially disposed hole 24 extending through the insert 
from the outer circumferential face 26 of a centrally located opening 25. 
This hole 24 is adapted to be disposed in axial alignment with threaded 
hole 18 through the narrow portion of the lathe dog member 10 so that the 
set screw 19 may be inserted through the bushed hole 18 and continue to 
extend into and through the threaded hole 24 to the central opening 25. 
The central opening 25 in the lathe dog insert is adapted to receive a 
workpiece to be turned in the lathe and which is secured in the lathe dog 
by tightening the set screw 19 through the aligned holes 18 and 24 into 
rigid engagement with the workpiece. Thus the lathe dog turns with the 
workpiece and while the workpiece opening 25 in the insert 20 is centrally 
disposed, the opening 11 in the disc-shaped lathe dog member 10 is located 
substantially to one side of the center of the disc-like lathe dog so that 
the lathe dog in operation moves in an orbit about the center of the 
workpiece and the insert 20, since the centerline of the workpiece and the 
axis of the opening 25 are substantially coaxial, thereby functioning like 
a cam to obtain the sliding or wiping action necessary to its operation of 
pushing aside any member coming in contact therewith while it is rotating. 
The insert member 20 may be provided in various sizes to accept workpieces 
of different sizes and for this purpose the inserts may be furnished in 
sets containing a plurality of such insert members with each insert having 
the same overall size, but each having a central opening 25 of a different 
size from the central opening of any other insert in the set and 
preferably graduated as to size to provide a selection of sizes in 
successive graduations affording complete sets of inserts adapted to fit 
any size work piece in increments of one sixteenth inch or one eighth 
inch, as preferred. 
The lathe dog member 10 is provided with a laterally projecting pin 30 
which extends outwardly from one face of the member 10. This projecting 
pin functions similarly to the usual tailpiece on a typical lathe dog and 
is adapted to engage into a radial slot provided in the usual face plate 
of a lathe to drive the lathe dog and associated workpiece in the manner 
typical of standard lathe operations and procedures in the average machine 
shop. The lathe dog member 10 is shown as being fabricated from a solid 
section disc-like member but this may be constructed as a hollow section, 
if preferred and preferably is made of aluminum, or similar metal, or if 
desired, the disc-like member 10 might be made from a suitable plastic 
material. In practice the lathe dog member 10 is statically balanced to 
provide the desired operation of the installation in practice. 
From the foregoing it will be seen that a safety lathe dog has been 
provided which is in the form of a disc-like member having an 
eccentrically located opening in which is mounted any one of a set of 
removable insert members each of which has a centrally located opening for 
receiving a workpiece so that the workpiece and insert are on center with 
respect to the lathe centers, but the lathe dog being mounted off center 
moves in an orbit about the center of the workpiece to effect a sliding or 
wiping action with respect to any member coming into contact with the 
rotating lathe dog whereby to push such member away from possible injury 
rather than exert the striking force normally associated with the 
operation of the typical lathe dog heretofore.