Collet stop

The collet stop (1) comprises a clamping disk (15) placeable on the edge (17) of a collet (2) and a chuck body (21) displaceable relative to this clamping disk, having three radially unscrewable tapped bolts (25, 26, 27) which rest against the rearward ends of the slots (6) of a collet. By means of a tightening screw (31), the chuck body (21) can be displaced relative to the clamping disk (15), and the conical ends (34), provided with a hexagonal socket, of the tapped bolts caused to rest against the slot ends. Screwed into the tightening screw (31) is a threaded rod (48) which is provided at its end with a stop disk (52) for the workpiece to be machined. The collet is not crushed or deformed by the collet stop, the collet stop being insertable as a whole into the collet from the rear. As a result of the conical ends (34) of the tapped bolts (25), the collet stop (1) rests against all three ends (38) of the slots (6) of the collet.

BACKGROUND OF THE INVENTION 
The present invention relates to a collet stop as well as to a stop disk 
and a stop bolt for a collet stop. 
In a known collet stop, by driving a tightening screw into a chuck body, 
three balls disposed regularly over the periphery of the chuck body, 
supported in corresponding openings, are pressed radially outward by the 
tightening screw and brace the chuck body in the annular area of the 
collet. Thereby, however, this part of the collet is crushed, whereby the 
collet can no longer be inserted in the adapter sleeve. Previously known 
from EP-A-0 356 575 is a chuck for a turning lathe in which an insert is 
screwed into an insert nut, which may lead to deformation of the clamp. 
Conical surfaces at the end of the collet and on the insert cause a 
deformation of the clamp. Radially outward projecting noses disposed on 
the insert nut are so formed that, as a rule, only one nose will rest 
against the end of a slot of the collet since the slots are worked 
inaccurately. Furthermore, on account of the quick change of the direction 
of rotation from left to right in turning lathes in the subject of the 
above-mentioned publication, the insert may loosen. 
SUMMARY OF THE INVENTION 
It is a task of the present invention to avoid the disadvantages of the 
prior art and to develop a collet stop for a conventional collet in such a 
way that during the machining of the workpiece chucked in the collet, the 
stop for the workpiece cannot be axially displaced by the forces occurring 
during the machining, and the collet is not crushed or deformed by the 
collet stop. The collet stop shall be insertable in the collet as a whole 
from the rear. This is achieved according to the invention by features 
described herein. Furthermore, it is a task of a preferred embodiment of 
the present invention to form the collet stop in such a way that the stop 
takes place at the edge of all slots of the collet, even if the slots are 
inaccurately worked. This is achieved according to the invention in that 
the chucking elements are formed tapering or conical at their outer ends. 
A further task of a preferred embodiment of the present invention is to be 
able to displace the chucking organ with the chucking elements axially on 
the collet from outside. This is achieved according to the invention by at 
least one clamping means extending through the chucking organ. 
Furthermore, it is a task of a preferred exemplified embodiment of the 
invention to lock a stop disk placed on the stop means, or a stop bolt, 
against axial displacement. This is achieved according to the invention by 
a setscrew extending through the stop means. 
Exemplified embodiments of the invention, as well as their use, are 
described in detail below with the aid of the enclosed drawing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The first exemplified embodiment of the collet stop is described with the 
aid of FIGS. 1 to 3. The complete collet stop 1 is inserted in a collet 2 
from the rear. The end face 3 of the collet is pressed against the flange 
of a non-depicted headstock of a turning lathe, the flange engaging an 
annular recess 4 on the end face 3 of the collet. Seated on the outside of 
the collet 2 is a likewise non-depicted adapter sleeve which comprises an 
inner cone that presses against a cone 5 of the collet. Headstock, adapter 
sleeve, and collet are previously known from the prior art. The collet 2 
is provided, uniformly distributed over the circumference, with three 
slots 6, 7, and 8 which run rearward from the end face 3 and end at a 
non-slotted annular area 9. The collet has at the front three clamping 
jaws 10, 11, and 12 which bound a receiving bore, provided with circular 
grooves 13, for receiving a non-depicted workpiece. The collet stop 1 
comprises a clamping disk 15 which is inserted in the collet 2 from the 
rear, an appendage 16 of the clamping disk resting against the rear edge 
17 of the collet. Disposed in an annular recess 136 of the clamping disk 
15 is an annular nut 20 having an internal thread 19, provided with two 
axial bores 18 and 137 for insertion of a wrench. Disposed in the region 
of the slots 6, 7, and 8 is a chuck body 21 having an annular appendage 
141 which, together with the complete collet stop 1, is inserted in the 
collet from the rear, three uniformly spaced, radially extending tapped 
bolts 25, 26, and 27 provided with threads 22, 23, and 24 being screwed 
into the chuck body during insertion of the complete collet stop 1. The 
chuck body 21 is provided with an internal thread 28. The chuck body 21 is 
provided on its circumference with an O-ring 29 for retaining the coolant 
during the machining of the workpiece chucked in the collet. Screwed 
together with the annular nut 20 and the chuck body 21 is a tightening 
screw 31 having an external thread 30. Between the clamping disk 15 and 
the tightening screw 31, a spacer disk 32 is disposed. The tightening 
screw 31 has a milled knob 33 for twisting the tightening screw 31 
relative to the chuck body 21. Upon twisting of the tightening screw 31 
clockwise, the chuck body 21 is displaced to the rear, thus toward the 
left according to FIG. 1. The annular appendage 141 of the chuck body 21 
engages around an annular shoulder 142 of the clamping disk upon 
displacement of the chuck body 21. Before tightening of the tightening 
screw 31, the tapped bolts 25, 26, and 27 are screwed out of the chuck 
body 21 by means of a hexagonal wrench until their upper conical ends 34, 
35, and 36 are in the region of the wall 37 of the collet. Through 
tightening of the tightening screw 31, the conical ends 34, 35, and 36 of 
the tapped bolts, provided with a hexagonal socket (Inbus), are pressed 
against the rearward ends 38, 39, and 40 of the slots 6, 7, and 8. If the 
slots are inaccurately worked, then by adjustment of the tapped bolts, as 
a result of the conical formation of their ends 34, 35, and 36, it can be 
achieved that the tapped bolts rest everywhere against the ends 38, 39, 
and 40 of the slots. The displacement movement of the chuck body 21 
relative to the tightening screw 31 is guided by three cap screws 41, 42, 
and 43. These screws are driven into the chuck body 21 and move in 
cylindrical recesses 44, 45, and 46 of the clamping disk 15. A threaded 
pin 63 having a hexagonal socket (Inbus) extends, as is apparent from FIG. 
2, in axial direction through the rear part of the tightening screw 31 and 
presses on the spacer disk 32 and thereby secures the tightening screw 31 
against loosening. Screwed into an internal thread 47 of the tightening 
screw 31 is a threaded rod 48 having an external thread 49. The threaded 
rod 48 is provided at its rearward end with a hexagonal socket (Inbus) 50 
for adjustment of the threaded rod 48 in the longitudinal axis. At its 
front end, the threaded rod 48 is provided with a shoulder 51, on which 
shoulder a stop disk 52 is set. Depending upon the inside diameter of the 
collet between the clamping jaws, stop disks for the workpiece to be 
machined of different diameter may be used. Stop disks 52 are used when 
the diameter of the workpiece is greater than the diameter of the threaded 
rod. In the longitudinal axis of the threaded rod 48, a hexagonal-socket 
setscrew 53 is provided, which is driven by means of an external thread 54 
into an internal thread 55 of the threaded rod. The conical front end 56 
of the setscrew presses the front part 51 of the threaded rod somewhat 
apart through pressure action upon an inner projection 135 of the threaded 
rod and thus secures the stop disk 52 against pulling away from the 
threaded rod when the machined workpiece, which is possibly still adhering 
to the stop disk 52 through an oil film, is removed from the collet. The 
rearward end 57 of the threaded rod is preferably likewise milled. Through 
twisting of the threaded rod 48, the desired stop depth for the workpiece 
to be machined is set. By means of a threaded pin 59 provided with a 
hexagonal socket 48, the threaded rod 48 may be secured against twisting. 
The threaded pin braces the tightening screw 31 in the region of a slot 60 
in that the pin is pressed against the rear surface 61 of the slot. 
In FIG. 2, a view from the left according to FIG. 1 of the collet is 
depicted. From this figure, the threaded pin 63 provided with a hexagonal 
socket 62 for securing the tightening screw against loosening is 
additionally also depicted. The threaded pin 63 presses in the locking 
position against the spacer disk 32 (see also FIG. 3). Instead of three 
slots 6, 7, and 8, the collet might also have four slots. Therefore, 
preferably six bores provided with thread are provided at the periphery of 
the chuck body for the reception either of three or of four tapped bolts. 
In FIG. 3, a collet 65 having a receiving bore 66 for workpieces of small 
diameter is depicted. Accordingly, the clamping jaws 67 and 68 also have a 
greater wall thickness. Instead of the stop disk, a stop bolt 69 is 
provided for workpieces of the same or smaller diameter than that of the 
threaded rod 48. The stop bolt 69 has at its rearward end a conically 
widened part 70 which is followed by a cylindrical sleeve 71. The 
cylindrical sleeve 71 is slipped onto the appendage 51 of the threaded rod 
48 and secured by the setscrew 53. Otherwise the collet stop according to 
FIG. 3 is constructed the same as that according to FIGS. 1 and 2. The 
threaded rod 48 is provided in its region facing the stop disk 52 or the 
stop bolt 69 with three slots 138 reaching up to the front end of the 
shoulder 51 so that the shoulder 51 may be spread apart for holding the 
stop disk or the stop bolt. 
The collet stop 72 for the collet 73 according to the second embodiment is 
depicted in FIG. 4. The collet stop according to this figure is suited to 
dividing apparatuses for drilling and milling. In this connection, the 
dividing apparatus is closed in the rear region of the collet so that no 
parts as in the first embodiment may project out rearwardly. The chuck 
body 74 inserted in the collet from the rear has at its periphery two 
spaced O-rings 75 and 76 for sealing against coolant. By means of an 
appendage 77, the chuck body 74 rests against the rear edge 78 of the 
collet. Three hexagonal-socket setscrews 79 are disposed parallel to the 
axis of the collet at regular intervals in the chuck body. The setscrews 
79 have a rear part 80 with an external thread 81 which is screwed into an 
internal thread 82 of a cylindrical opening 83 in the chuck body. With the 
aid of the rear hexagonal socket (Inbus) disposed in the setscrew, the 
setscrew may be adjusted by means of a hexagonal wrench. The front part 84 
of the setscrew is formed tapering. Upon insertion of the chuck body 74 in 
the collet, the setscrews 79 are in a rear position, and the three 
clamping studs 86 situated in radially running openings 85 do not project 
beyond the outer circumference 87 of the chuck body 74. Upon turning-in of 
the setscrews 79, the clamping studs 86 are displaced outwardly and 
pressed against the rear edge 88 of the slots 89 and secure the chuck body 
74 in the machining position. The clamping studs 86 are formed tapered in 
the front region 90, preferably domed, which makes it possible to stop all 
three clamping studs 86 at the rear edge of the slots 89 even when the 
three slots 89 of the collet are not worked exactly the same. Through an 
axially running central opening 91 of the chuck body 74 there runs an 
adjustment bolt 92 variable in length according to what distance from the 
end face 93 of the collet the workpiece to be machined is supposed to be 
stopped. Disposed in an axially running cylindrical opening 95 provided 
with an internal thread 94 is a clamping screw 97 provided with external 
thread 96 and having a hexagonal socket 98. The clamping screw 97 acts 
upon a chuck lever 99 disposed in the front region of the chuck body 74, 
engaging about the adjustment bolt 92, by means of which chuck lever the 
adjustment bolt 92 can be locked in the desired position. The adjustment 
bolt 92 has at its front end a shoulder 100 in which a circlip 101 is 
embedded. Upon slipping of the stop disk 102 with the cylindrical sleeve 
103 onto the appendage 100, the stop disk 102 is held on the adjustment 
bolt 92 by the circlip 101. 
Also in the second exemplified embodiment according to FIG. 4, instead of 
the variable stop disk for workpieces to be machined having a larger 
diameter than the diameter of the adjustment bolt 92, a stop bolt, as in 
FIG. 2, might be used for workpieces of the same or smaller diameter than 
the adjustment bolt 92. 
In FIG. 5, a third embodiment of the invention is depicted. The collet stop 
104 according to this embodiment is, as in the case of the second 
embodiment according to FIG. 4, likewise used whenever the collet 105 is 
utilized in dividing apparatuses for drilling or milling. Inserted in a 
clamping disk 106 is a tapped sleeve 108 provided with an external thread 
107. An appendage 109 of the clamping disk 106 rests against a rear edge 
110 of the tapped sleeve 108. An annular nut 111 is screwed on the tapped 
sleeve 108 and rests against the appendage 109 of the stop disk. 
Furthermore, a threaded chuck body 112 is screwed on the tapped sleeve 
108. Disposed at regular intervals in the clamping disk 106 are three 
tapped bores 113 into which three setscrews 114 are driven. The setscrews 
114 have a part 115 formed tapering at the front which engage in bores 
116, running parallel to the longitudinal axis of the collet stop, of 
three clamping studs 117 disposed at regular intervals in the threaded 
chuck body 112. The clamping studs 117 are displaceably disposed in radial 
bores 118. The desired length L between an appendage 120 of the stop disk 
resting against the rear edge 119 of the collet and the rear edge of the 
bore 118 is pre-set by twisting of the threaded chuck body 112 on the 
tapped sleeve 108 outside the collet. According to the diameter of the 
workpiece to be machined and the required chucking length, a suitable 
adjustment bolt 121 as well as a suitable stop disk 122 are selected and 
plugged into the exact bore 138 of the tapped sleeve 108. The stop disk 
122 rests by means of a cylindrical sleeve 123 on an appendage 124 of the 
adjustment bolt 121 and is held by means of a circlip 125. The complete 
collet stop is inserted, with setscrews 114 screwed all the way out, into 
the collet 105 from the rear, it being heeded during insertion that the 
three clamping studs 117 agree with the clamp slots 128. The setscrews 114 
are evenly driven in and the tapered, preferably domed upper part 126 of 
the three clamping studs 117 thereby pressed against the upper edge 127 of 
the three clamp slots 128. A tightening screw 131 provided in the rear 
region with a thread 130 is screwed in an axially running bore 129 of the 
clamping disk 106. By tightening this tightening screw 131, its front part 
132, which is guided in an axial bore 133 of the threaded chuck body 112, 
is pressed against a chuck lever 135 connected to the threaded chuck body 
and engaging about the adjustment bolt, the adjustment bolt 121 being 
thereby securely clamped in the desired position. The threaded chuck body 
112 is provided on its outer circumference with an O-ring 135 for 
retaining the coolant. Instead of the stop disks 122, stop bolts might 
also be used as in the first and second embodiments. 
FIG. 6 shows a partial section through the rear part of a fourth 
exemplified embodiment of a collet stop. A threaded rod 144 provided with 
a milled end 143 extends axially through the tightening screw 145 with the 
milled knob 146. Disposed in the collet concentrically with the tightening 
screw in the annular region 147 and partially in the slotted region 148 is 
a chuck body 149, three or four radially extending tapped bolts 150 
provided with threads being disposed in matching tapped bores in the chuck 
body. Six bores are provided. The tapped bolts are distributed on the 
circumference in such a way that the collet stop can be used both for a 
collet having three slots and for a collet having four slots. Set on the 
rear edge of the annular region 147 is a clamping disk 151. Several pins 
152 are provided, which extend into corresponding openings in the clamping 
disk 151 and in the chuck body 149. Disposed at the end of the tightening 
screw 145 remote from the knob 146 is a clamping ring 153. The tapped 
bolts 150 are formed conical at their ends projecting into the slots of 
the collet and have a hexagonal socket at this end. Screwed in the knob 
146 is a threaded pin 154 extending parallel to the threaded rod, which 
pin is provided at its end remote from the pin-shaped part 155 with a 
hexagonal socket 156 for twisting. Provided in the handle is a slot 157 
which extends perpendicular to the longitudinal axis of the collet stop. 
Through twisting of the threaded pin 154, the pin-shaped part 155 presses 
on the clamping disk 151, whereby the tightening screw 145 is braced in 
the region of the slot 156. The threaded rod 144 can thereby be secured 
against twisting. Furthermore, upon stopping of the pin-shaped part 155 on 
the clamping disk 151, the tightening screw 145 is secured against further 
twisting. In this embodiment, the entire clamping disk 151 is hardened. In 
contrast to the embodiment according to FIGS. 1 to 3, the two locking 
operations can be undertaken with a single threaded pin. 
The collet stop according to all embodiments is suited for use with 
conventional collets. For each collet stop, a set of stop disks and stop 
bolts of variable diameter can be made available.