The present invention relates to a device for the accurate axial adjustment of a workpiece in a chuck, comprising at least two jaws,radially adjustable for holding the workpiece. The invention also relates to a method for manufacturing such a device.

In the machine industry there are several machines provided with chucks, for machining workpieces by turning, cutting etc. Depending upon the type of workpiece there are different demands on the axial adjustment of the workpiece in the chuck. Especially when manufacturing in series it is important, that the set of the workpiece in the chuck can be performed quickly and in a reproducible axial position.

There are different such devices for such axial adjustment of workpieces in chucks, but they are often complicated and do not enable accurate adjustment. In the German Patent Specification No 684401 there is suggested a device, consisting of two flanges, that are provided with hubs, that can cooperate according to the telescope principle.The flanges may be set axially in mutual relationship to each other by screw devices. It is obvious, that this device is , on the one hand, complicated, but on the other hand also probably needs some gauge or the like for setting, and that it is more or less impossible to achieve reproducible axial positions of a workpiece in a chuck, if the latter must be used for different purposes, so that the device must be set once more for any new specific utilization.

The object of the present invention is to provide a device of the type mentioned introductorily, that is simple when used, and cheap in manufacture, and that allows a highly accurate axial adjustment of a workpiece in a chuck.

The object is also to suggest a method for the manufacture of such a device.

According to the invention a device of the type mentioned introductorily is characterized in that it comprises at least of one body, limited by a first and a second plane surfaccwhich surfaces are parallel, on a well defined distance from each other, which distance equals the axial height h of the body, the body being provided with recesses at least for the radial movements of said jaws,which recesses enable the fit-up of the body with the first surface against the axial limiting surface of the chuck,the other surface defining the axial . position of the workpiece in the chuck.

The accuracy of the axial adjustment of a workpiece is determined by the surface smothness of the first and second surface, and by the corresponding property of the axial limiting surface of the chuck.

Said height h is chosen according to the demand, and may be e g 15 mm, 25 mm etc.

In a suitable embodiment of the invention the device comprises a series of bodies with axial heights h(l) - h(n) , chosen according to such a system, that a large number of total heights h can be obtained , according to the demand.

Considering easy handling and materials economy it is suitable to design the body in such a way, that it comprises branches, arranged in pairs on each side of each jaw.

It is practical to provide said body with at least one agneϋn position substantially in level with said first surface.In this way, the body can be brought easily and quickly into the correct position against the limiting surface of the chuck.

The device according to the invention can of course be manufactured in different ways.One economical way implies, that a profile is made from a material like plastic or an aluminum alloy , by extrusion or power pressing,whereafter said body is obtained by dividing of the profile perpendicularly against the elongation and machining of the created first and second surfaces to a desired height h and to a desired surface smothness. The latter is of course determined by the accuracy that is needed in the axial adjustment in the chuck.

A suitable economical method for the manufacture of the device according to the invention implies, that the profile is made with elongated recesses corresponding to maximal jaw width, but with protrusions on both sides of the recess along at least part of the radial extension of the recess, preferably in its radially seen outer end, enabling machining afterwards to adaptation to the desired jaw width. In this way there can be provided a whole assortment of devices according to the invention, for different jaw widths , with good manufacturing economy.

The invention is described in the following, reference being made to the enclosed figures. of which figure 1 shows, in perspective, a first embodiment of a device according to the invention,

figure 2 shows, in perspective a second embodiment of the device according to the in¬ vention, figure 3 shows a plan view of the device in figure 2, and figure 4 shows a cross section of a profile for the manufacture of devices according to the invention, for varying jaw widths .

The device shown in figure 1 is manufactured from a circular cylindrical extruded profile from an aluminum alloy. This profile has been divided into plates with the axial height h. Such a plate is limited by a first gable or side 1 and a second gable or side 2 (not shown in the figure). These gables are, after dividing the profile, surface ground to a surface smothness, that is determined by the accuracy, that is needed for the objective in question.The gables are parallel, in the distance h, which measure means the axial height of the device or body. The device is intended for utilization in a chuck with three jaws, and is thus provided with three recesses 3 in the body. These recesses show radial symmetry planes, of which one is indicated with a dotted line.

The embodiment of the device, that is shown in figure 2, differs from that in figure 1 mainly in that the recesses 3 are here surrounded by branches 4 and 5, which means a substantial saving in material. The branches 5 are, in this embodiment, provided with outer protrusions 6, in which permanent magnets 7 are placed in level with the first surface. The permanent magnets have for an object to keep the devices tightly against the axial limiting surface of the chuck.

Figure 3 shows the device in figure 2 from above.

As has been mentioned, the devices according to the invention are suitably manufactured by extrusion or power pressing of a profile from e g an aluminum alloy. A suitable method for manufacture is illustrated in figure 4, that shows the cross section of a profile for the manufacture of devices for different jaw widths, with a maximal width bl, as is indicated in the figure. The cross section shows branches 8 and 9,with an outer protrusion 10 on the latter for providing permanent magnets. The branches 8 and 9 are, respectively, in their radially outer ends provided with inner protrusions 11 and 12, that between themselves symmetrically in relationship to the branches 8 and 9, define a smaller jav. width b2. The inner walls on the inner protrusions 11 and 12 are in this case plane, and may be adapted to a chuck with the jaw width b2 minus tolerance. By machining of these protrusions the device can be adapted to an assortment of chucks with rising jaw width up to said maximal jaw width bl . This method of manufacture is efficient and economical.