Mandrels for ring working and bracelet working are rigidly supported by a specially adapted mandrel holder secured to a supporting base. A chucking opening is provided in the holder for receiving the mandrel and a fastener is provided for securing the mandrel to the holder. The fastener is adjustable to permit a ring mandrel to be positioned so that selected working positions on the mandrel can be disposed in close proximity to the holder.

The present invention pertains generally to jeweler's tools and more 
particularly to mandrels and related tools employed in the silver and gold 
crafts for working with rings, bracelets and the like. 
It has been a practice in the prior art to employ ring mandrels which are 
tapered or have stepped cylindrical surfaces to accommodate rings of 
different sizes at respective working positions on the mandrel. Typically, 
such mandrels are about twelve inches long and have steps progressively 
increasing in diameter from three-eighths inch at the small end to 
fifteen-sixteeths inch at the large end. A shank is usually provided at 
the large end of the mandrel for insertion into a holder for securing the 
mandrel during ring working operations. 
Heretofore a disadvantage of such tools has been the tendency of the 
mandrel to flex and bounce in the holder particularly when the craftsman 
shapes a ring by repetitively pounding and striking it in a manner well 
known to those skilled in the art. It will be appreciated that this 
flexing effect becomes progressively more pronounced the more the working 
position is removed from the holder. The problem is most severe at the 
small end of the mandrel at which most of the impact delivered to the ring 
will typically be absorbed by the movement of the mandrel, thus reducing 
the shaping effect of each impact to the ring. 
One solution to the aforementioned problem is to provide several mandrels 
of shortened length so that the distance from the smallest ring working 
position to the holder is only several inches, thus minimizing the effect 
of mandrel flexing. It will be recognized that another approach to the 
problem which would substantially eliminate the effect of mandrel flexing 
would be to provide one short mandrel for each ring size so that the 
impacts of ring working will always be applied adjacent to the holder. 
It would be desirable, however, to provide a solution to the aforementioned 
problem of mandrel flexing without employing more than one mandrel. This 
objective is accomplished in accordance with one important feature of the 
invention herein disclosed by the provision of a jeweler's tool which is 
adaptable to secure a mandrel at selected positions relative to a mandrel 
holder so that working positions of different diameters on the mandrel can 
be positioned in close proximity to the holder. 
Another disadvantage of prior art jeweler's tools is that they tend to be 
very specially adapted to particular operations. It would therefore be 
desirable to provide a more versatile tool useful for more than a single 
operation. This object is accomplished in accordance with another 
important feature of the invention herein disclosed by the provision of a 
jeweler's tool which is adaptable to secure either a ring mandrel of 
circular cross-section or a bracelet mandrel of an oval-shaped 
cross-section by means of a single mandrel holding mechanism.

Referring now to the figures, a jeweler's tool is illustrated and 
designated generally by reference numeral 10. With particular reference to 
FIGS. 1 and 2, the jeweler's tool is shown in the manner in which it is 
employed with a ring mandrel 12 of essentially conventional construction 
having a plurality of working positions disposed in stepped fashion along 
the length thereof. Each working position has a cylindrical surface of 
about one inch in length with a given diameter corresponding to a 
particular ring size. Inasmuch as the ring mandrel is essentially 
conventional, the number and sizes of ring working positions will not be 
described in detail. It will be appreciated, however, that various 
different ring mandrels from that specifically illustrated herein have 
useful application to the present invention. For example, the present 
invention also contemplates the use of a continuously tapered ring mandrel 
(not shown). 
The jeweler's tool 10 includes a supporting base 14 to which a mandrel 
holder 16 is rigidly secured, such as by means of the threaded stud 18 
seen in FIG. 2. The holder 16 is provided with a chucking opening 20 at a 
convenient distance from the base 14. The chucking opening 20 is formed by 
two intersecting eccentric cylindrical bores 22 and 24, which are 
graphically depicted in FIG. 3. The bores 22 and 24 intersect to define 
gripping edges 26 and 28, which preferably lie in a plane which includes 
the center of the smaller cylindrical bore 24. 
Referring again to FIG. 1, the mandrel 12 includes a working position 30 of 
smallest diameter at one end thereof and a working position 32 of largest 
diameter at the other end thereof. (It will be appreciated that the 
position 32 might alternatively serve as a shank and the adjacent 
cylindrical surface would then serve as the largest ring working 
position.) The positions that the mandrel 12 would assume when the largest 
and smallest ring working positions are disposed within the holder 16 is 
illustrated by the dashed outlines 30 and 32 in FIG. 3. 
It will be appreciated that the larger bore 22 has a diameter which is 
greater than the diameter of the largest ring working position 32. A bore 
with a diameter of 0.965 inch is suitable for most purposes as jeweler's 
mandrels typically have a shank with a diameter between 0.875 and 0.955 
inch and a largest ring working position of 0.945 inch. The smaller bore 
24 has a diameter which is less than the diameter of the smallest ring 
working position to be disposed within the holder 16. By using bores of 
such sizes, the gripping edges 26 and 28 will be located effectively to 
bite into corresponding surface portions of any desired working position 
of the mandrel 12. A smaller bore of 0.5 inch is suitable for most 
standard ring mandrels. 
In order to force the mandrel 12 against the gripping edges 26 and 28, an 
adjustable fastener 40 is provided as will now be described with 
particular reference to FIG. 2. The fastener 40 includes a cylindrical 
head or nob 42 and a threaded stud 44 extending axially from the nob 42 as 
shown. The threaded stud 44 passes through a correspondingly threaded hole 
in a side wall of the holder 16. The stud 44 passes into the opening 20 in 
alignment with the centers of the bores 22 and 24 so that by appropriate 
rotation of the nob 42 the end of the stud will engage the mandrel 12 and 
force it against the gripping edges 26 and 28 in the manner indicated. 
From the foregoing description of the jeweler's tool 10 as applied with the 
ring mandrel 12, it will be appreciated that any selected working position 
upon the ring mandrel 12 can be disposed either adjacent to or within 
several positions in proximity to the holder 16 so that ring working 
operations on the selected position can be done with a minimum of mandrel 
bounce or flexing. 
It should be noted that the amount of mandrel flexing and bounce can be 
further minimized by clamping the base 14 to a rigid supporting table. 
However, the tool 10 is adaptable so that ring working operations can 
proceed without securing the base 14 in such a fashion since the base 14 
and holder 16 are provided with sufficient mass to absorb the normal 
impact applied during ring working operations. Preferably the base 14 will 
have sufficient mass and hardness that its smooth upper surface can be 
used as a jeweler's anvil. 
Now referring to FIGS. 4 and 5, an adaptation of the jeweler's tool 10 for 
use with a bracelet mandrel 50 will be described. The bracelet mandrel 50 
has a single oval-shaped working surface 52. At one end of the mandrel 50 
is a peripheral wall 54 from which a cylindrical shank 56 extends 
outwardly. The shank 56 has a diameter slightly smaller than the diameter 
of the large cylindrical bore 22 so that the shank 56 will snugly fit into 
the chucking opening 20. The shank 56 defines a threaded axial opening to 
receive the threaded stud 44 of the fastener 40 in the manner shown. 
Accordingly, the bracelet mandrel 50 can be rigidly secured to the holder 
16 by tightening down the fastener 40 until the head 42 tightly abuts one 
surface of the holder and the peripheral wall 54 tightly abuts the 
opposite surface thereof as depicted in FIG. 5. It will, of course, be 
appreciated that the orientation of the working surface 52 of the mandrel 
50 can be varied simply by loosening the fastener 40, making an adjustment 
to the position of the mandrel 50 and then retightening the fastener 40 to 
once again secure the mandrel 50 rigidly in place. 
Although a preferred embodiment of the invention and two specific 
applications thereof have been described in detail, it will be understood 
that various modifications, substitutions and alternatives are within the 
spirit and scope of the invention as defined by the appended claims. For 
example, the jeweler's tool of the present invention can be used to secure 
a variety of mandrels and jeweler's implements other than those 
illustrated.