A lathe workholder which allows a conventional three jaw chuck to turn quadrilateral stock having a first unitary workholder member interposed between two of the jaws and the stock and having a crotch portion which straddles two sides of the stock; a second workholder member interposed between the remaining jaw and the stock and diametrically opposed from the first member and having a crotch portion which straddles the remaining two sides of the stock, so that the conventional three jaw chuck can be utilized to retain quadrilateral stock and lathe down time is reduced.

BACKGROUND OF THE INVENTION 
The following invention relates generally to workholders for lathes which 
allows a conventional three jaw chuck to turn quadrilateral stock 
material. 
More particularly, the instant invention is directed to an instrumentality 
for obviating the necessity of tearing down a lathe in its entirety when 
one is required to turn square stock. Frequently, it is necessary to turn 
square stock or rectangular stock in an operation which constitutes a 
minor portion of a turning job. In such cases, it has been required to 
remove the existing three jaw chuck system, install a four jaw chuck and 
thereafter put the work stock in for the turning operation and center the 
work stock. Once this operation has been completed, of course, the 
original three jaw chuck must be replaced. Even a highly skilled artisan 
must spend perhaps 30 minutes or more for first removal and then 
replacement of the four jaw system, without the centering operation even 
considered. This provides a nettlesome problem, particularly when the 
turning operation is for a relative small quantity and the machine must be 
reconverted almost immediately thereafter. 
There have been known prior art attempts in causing conventional three jaw 
chucks to lend themselves to utilization by square stock. The instant 
invention is easily distinguished over these known prior art techniques in 
that the effort involved in placing the workholder members according to 
the instant application is no more cumbersome than the effort required in 
placing the square stock in the jaws of the lathe. Thus, there is no 
discernible investment of time that is required for utilization of the 
instant device, particularly when contrasted with the known prior art. 
Further, the instant invention is distinguished over the known prior art in 
that an instrumentality has been provided which allows a conventional 
three jaw chuck to turn quadrilateral stock which is formed preferably 
from first and second unitary workholder members diametrically opposed 
within a circumscribed area defined by the innermost faces of the three 
jaw chucks, each member having a somewhat V-shaped portion defining a 
crotch which engages respectively two sides of the quadrilateral stock. 
One of the members is caused to lay against two of the conventional jaws 
with the other member diametrically opposed therefrom. When the jaws are 
clamped tight, an aligned secured piece of square stock will be held 
without any of the wobble or precession that normally accompanies 
conversion from one known prior art system to another without centering. 
SUMMARY AND OBJECTS OF THE INVENTION 
Accordingly, this invention has as its objective the provision of a new and 
novel lathe workholder which allows a conventional three jaw chuck to turn 
quadrilateral stock. 
It is yet a further object of this invention to provide a device as 
characterized above in which quadrilateral stock of varying dimensions can 
be accommodated. 
It is yet a further object of this invention to provide a device as 
characterized above which is durable in construction, lends itself to mass 
production techniques, and is extremely safe to use. 
A further object of this invention contemplates providing a device as 
characterized above which substantially and materially alters the down 
time required in converting conventioal lathes from one system which 
accommodates non-square stock to one which does. 
A further object of this invention contemplates providing a device as 
characterized above which eliminates the centering step normally required 
in the prior art conversion. 
A further object of this invention contemplates providing a device as 
characterized above which addresses itself to the long-felt yet heretofore 
unfulfilled need of providing a means for accommodating different 
geometrically figured stock materials without excessive down time, 
particularly advantageous when the conversion is so temporary due to a 
small production requirement that the prior art techniques spend more time 
in the conversion than the actual lathe operation. 
These and other objects will be made manifest when considering the 
following detailed specification taken in conjunction with the appended 
drawing figures wherein there has been provided an instrumentality which 
allows a conventional three jaw chuck on a lathe to be adapted to turn 
quadrilateral (square or octagonal) stock including first and second 
unitary workholder members, one of which is interposed between two of the 
jaws and the stock and the second member is interposed between the 
remaining jaw and the stock diametrically opposed from the first member, 
each of the members having a substantially V-shaped crotch portion adapted 
to gird respectively two sides of the quadrilateral whereby the operation 
for inserting the square stock with the workholder members takes 
substantially the same amount of time as placing conventional stock 
material within the lathe workholder chuck for normal lathe operations.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings now, wherein like reference numerals refer to 
like parts throughout the various drawing figures, reference numeral 10 is 
directed to the lathe workholder according to the present invention. 
As shown in FIG. 4, a first unitary workholder member 20 or base block is 
formed preferably from a durable non-deformable material and preferably a 
hardened metal such as steel. The base block 20 includes a base portion 
(first base) 1 and a pair of upwardly and outwardly extending side walls 2 
emanating from a first end from the base 1 at an angle alpha with respect 
to an extension of the base and an outer face of the wall. In a preferred 
embodiment, the angle alpha equals 60.degree.. 
Each side wall terminates at a second, opposite end with two inwardly 
extending shelf portions 3 parallel to the base portion 1, the shelf 
portions 3 in turn allowing a transition in which a V-shaped crotch (first 
crotch) 4 is downwardly and inwardly declinated with respect to the base 
1. The two walls (inner faces) forming the V-shaped crotch have a 
subtended angle theta which in a preferred form is 90.degree. and 
therefore is not parallel with walls 2. The subtended angle between the 
two (i.e. upwardly extended lines of sidewall 2 and crotch wall 4) is 
preferably 15.degree.. The side wall and shelf portion has at a line 
extending beyond the shelf providing a subtended angle beta with respect 
to the side wall which in a preferred form is 120.degree.. 
In a preferred form, the base portion 1 has an overall dimension of 5/8", 
each shelf is 3/8", and the height of the base block or first unitary 
workholder member is 11/4" with an overall length L of 21/2". The overall 
wingspan taken from shelf 3 extremities is 2". 
Similarly, FIG. 1 reflects one form 30 of a second workholder member which 
may be used in place of the element 50 shown in FIG. 7. Alternatively, the 
element 40 may be substituted therefor depending upon the dimension of the 
4-sided work stock to be turned as will be explained hereinafter. 
Irrespective, the second workholder member 30 of FIG. 1 includes a second 
base having top wall (outer face) 11 of a second base, integral with the 
first end of a pair of normally and downwardly extending side walls 12 and 
further V-shaped crotch (second crotch) 14. Rather than having a 
horizontal shelf as shown in FIG. 4, a pair of canted walls 13 is provided 
communicating the V-shaped crotch 14 with the side walls 12. The angle phi 
denotes the degree of declination of the shelf 13 as it communicates the 
V-shaped crotch 14 with the side walls 12, and in a preferred form of the 
invention, the angle phi is 45.degree.. 
It can be seen that placement of the second workholder member onto the 
first workholder member or base block 20 will cause the shelves 13 to lie 
upon the walls formed by the V-shaped crotch 4 of the base block 20. Thus, 
for extremely small stock, an extremely strong interconnection exists 
between these workholder members, the stock and the convention three jaw 
chuck since the bearing surface of the shelf 13 against the V-shaped 
crotch 4 precludes wobbling or displacement of the stock given an 
appropriate dimension for the second workholder member. 
More particularly, note that the primary difference between that which is 
shown in FIG. 1 and FIG. 2 is the relative magnitude of the dimensions A 
and B which therefore can alter the dimension of the shelf 13 since in 
FIG. 1 the deepmost portion of the crotch 14 is coincident with the 
transition between the shelf 13 and the (inner faces) side wall 12, while 
in FIG. 2 that connection point has been changed somewhat. In any event, 
for bar stock less than 9/16", dimension A may vary between 3/16" and 
3/8". Dimension B may vary from 1/2" to 3/4" and the width C may be 2". As 
shown in FIG. 6, the overall length L of the second workholder member is 
also 21/2", similar to FIG. 5 of the base block 20. 
FIG. 3 is directed to the embodiment of the second workholder member shown 
in FIG. 7 which is adapted to accommodate bar stock 9/16" or larger. The 
dimension of the bar stock allows for the second workholder member to 
remain sufficiently high and away from the V-shaped crotch 4 of the base 
block that there is no practical necessity in having a shelf portion 13 
similar to FIGS. 1 and 2. Thus, a top wall 21 and a pair of normally and 
downwardly extending side walls 22 when combined with the V-shaped crotch 
24 define the entire second workholder in this embodiment. Here dimension 
A varies from 3/16" to 3/8", the width C is 3/4", and the height varies 
from 1/2" to 3/4". 
In use and operation, as suggested in FIG. 7, the base block 20 is allowed 
to nest upon the work engaging jaws of two of the three jaws and provides 
a cradle within which the square bar stock is placed. The second 
workholder member is caused to straddle the two sides of the bar stock 
remote from the base block, the second workholder member diametrically 
opposed from the base block such that the intersection of the walls (inner 
faces) of each crotch touch corners of the bar stock and a line passing 
through each crotch would bisect the stock material. Appropriate 
tightening of the conventioal three jaw chuck allows the expeditious 
utilization of this device without having to center the stock which is 
commonly required when converting from a three jaw to a four jaw system. 
Preferably, as shown in the figures, each of the inner faces as well as 
the outer faces of each workholder has a substantially planar portion for 
engaging, respectively the workpiece and the jaws. 
Having thus described the invention, it should be apparent that numerous 
structural modifications are contemplated as being a part of this 
invention as set forth hereinabove and as defined hereinbelow by the 
claims.