GB2059830A

GB2059830A - A spot weld milling tool

Info

Publication number: GB2059830A
Application number: GB8032469A
Authority: GB
Original assignee: Daimler Benz AG
Current assignee: Daimler Benz AG
Priority date: 1979-10-10
Filing date: 1980-10-08
Publication date: 1981-04-29
Also published as: GB2059830B; IT1128589B; DE2941041B1; FR2467038A1; DE2941041C2; IT8049847A0

Abstract

A spot weld milling tool for releasing spot-welded parts comprises a holding sleeve (1) with an integral cutter (4) and having an internal bore (2) in which a centering pin (3) is axially slidable against a compression spring (7) located in the bore. The centering pin (3) projects out of the free end of the holding sleeve and the pin (3) is provided with a snap ring (6) in a groove (5). The ring engages the bore frictionally by which axial movement of the pin (3) out of the free end of the bore (2) is controlled. <IMAGE>

Description

SPECIFICATION Spot weld milling tools The invention relates to a spot weld milling tool having a holding sleeve which can be secured in a milling spindle, a milling cutter part being located on the free end of this holding sleeve, in which a centering pin is located in a blind bored hole against a compression spring inside the sleeve, this centering pin being axially movably guided inside both the blind bored hole and the milling cutter part and having means for limiting axial travel of the pin, under the action of the compression spring, which would cause the pin to be pushed too far out of the blind bored hole or, possibly, completely out of the bored hole.

Spot weld milling tools are used for detaching spotwelded sheet metal parts from each other. For this purpose, a center punch is applied in the middle of the spot weld and the centering pin of the spot weld milling tool is sunk into the centre punch indentation. On applying pressure to the drilling machine, into which the spot weld milling tool is clamped, the holding sleeve is then displaced relative to the centering pun, and the milling cutter, which is fixed to the holding sleeve, is applied to the weld location, which is consequently milled-out by the cutter.

In the spot weld milling tool of the type mentioned, for example as disclosed by Swiss Patent Specification 402,561, the cutting part of the tool is a separate part, which must be screwed onto the sleeve-shaped end of the shaft of the milling tool or miller by means of a thread and a flange. A radially located locking pin is provided in order to secure the centering pin from being pressed out.

Generically similar millers are also known for example from German Offengegunlsschrift 2,826,957 in which the cutting part is integrally joined with the holding sleeve, this design resulting in a simpler and more compact miller.

If it is intended to design a miller of the initially mentioned type, which also has a cutting part integrally joined with the holding sleeve, difficulties and/or increased engineering and manufacturing costs arise in connnection with the arrangement and mode of operation of the locking pin.

The present invention is concerned to avoid these difficulties, and/or the engineering and manufacturing expense associated therewith, for the case in which it is intended to produce a generically conformable miller having a cutting part integrally joined with the holding sleeve.

According to the invention, there is provided a spot weld milling tool having a hold- ing sleeve which, in use, can be secured in a milling spindle, a milling cutter part being located on the free end of the holding sleeve, said sleeve having a blind bore disposed coaxially with the holding sleeve and being open at the free end of the sleeve, a compression spring being inserted into the blind bore and being supported on the bottom of the bore, a centering pin being located against the compression spring, the centering pin being guided axially for movement inside both the blind bore and the milling cutter part and having means for limiting the axial travel of the pin in said bore under the action of the compression spring, wherein the milling cutter part is integral with the holding sleeve and the centering pin is retained in the holding sleeve as a result of friction means, the resistance force due to this friction means against longitudinal displacement of thecentering pin being in equilibrium with the spring force corresponding to a predetermined state of relaxation of the compression spring.

A particularly advantageous embodiment of the ininvention comprises the provision of a circumferential groove on the centering pin and the insertion of a snap ring into this groove, this snap ring lying, under stress, against the inner wall surface of the blind hole.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawing, which shows a longitudinal section through a spot weld milling tool, having a holding sleeve and a centering pin.

The spot weld milling tool or miller shown in Fig. 1, consists of a holding sleeve 1, which has a blind bore 2, in which a centering pin 3 is coaxially guided. At the workpiece or free end, the holding sleeve 1 carries a ring-shaped miller 4, which is thus itelf machined integrally on the holding sleeve and is accordingly a part of the latter. The centering pin 3 possesses a circumferential groove 5, into which a snap ring 6 is inserted.

To assemble the milling tool, a compression spring 7 is first introduced into the blind bore and the centering pin 3 is then pushed in afterwards, against the force of the compression spring 7, the spring supported at its other end on the bottom 8 of the blind bore 2.

In operation, the point 9 of the centering pin 3 is initially inserted into a centre punch mark. On applying pressure to the drilling machine, the centering pin is then pressed into the blind bore 2, whilst the spring 7 is progressively compressed. On unloading the centering pin, the spring pushes the latter again approximately into position shown in the drawing. So that the centering pin cannot now fall out of the blind bore 2, of the holding sleeve 1, the snap ring 6 is provided, which, after relaxation of the spring, securely holds the centering pin by means of friction since this ring lies, with stress, against the inner wall surface of the blind bore 2.

To release any air, which is trapped in the blind bore, and to prevent air pressure changes influencing the movement, in the bore, of the centering pin, a passage 11 is provided, which possesses a comparatively small diameter relative to the diameter of the blind bore 2 and which leads, coaxially, to the end face 12 of the holding sleeve 1 remote from the miller 4.

The end of the holding sleeve remote from the miller 4 is dedigned in the form of the relieved chucking stub 13, which has a smaller diameter in relation to the remaining external diameter of the holding sleeve 1. This smaller diameter is advantageously ground and is advantageously not larger than 6 mm, so that it will also fit into small drilling machines. The chucking stub 13 further ensures that the spot weld miller is not inserted into the drill chuck more deeply than necessary.

Claims

1. A spot weld milling tool having a holding sleeve which, in use, can be secured in a milling spindle, a milling cutter part being located on the free end of the holding sleeve, said sleeve having a blind bore disposed coaxially with the holding sleeve and being open at the free end of the sleeve, a compression spring being inserted into the blind bore and being supported of the bottom of the bore, a centering pin being located against the compression spring, the centering pin being guided axially for movement inside both the blind bore and the milling cutter part and having means for limiting the axial travel of the pin in said bore under the action of the compression spring, wherein the milling cutter part is integral with the holding sleeve and the centering pin is retained in the holding sleeve as a result of friction means, the resistance force due to this friction means against longitudinal displacement of the centering pin be ing in equilibrium with the spring force corresponding to a predetermined state of relaxation of the compression spring.

2. A spot weld milling tool according to claim 1, wherein the centering pin is provided with a circumferential groove, into which a snap ring is inserted, this snap ring lying, under stress, against the inner wall surface of the blind hole.

3. A spot weld milling tool substantially as hereinbefore described with reference to the accompanying drawing.