GB2326610A - Compact toolholder assembly - Google Patents

Description

TOOLHOLDER ASSEMBLY This invention relates to toolholders for use on machine tools especially on automatic cam operated machines or lathes for producing small components such as screws, studs, bolts or the like.

Hitherto in such automatic machines and having regard to the limited tool space available at the workpiece, it has been the practice to employ holders ofthe kind having a brazed tungsten carbide finger or like member of which the tip is ground to a required shape for machining the workpiece. When the tip is worn, the toolholder is removed from the machine and the tip re-ground to the original shape.

This procedure is time consuming and expensive. In addition the brazed tools are not strong enough to withstand high speed operation. Typically the workpiece spindle speed is limited to 1600 rpm or thereabouts resulting in a surface machining speed of only 5 to 10 metres per minute.

The object of the invention is to provide an improved toolholder assembly in or for an automatic machine tool of the kind above referred to whereby small components can be satisfactorily machined at much higher spindle speeds and surface machining speeds resulting in much reduced machining cycle times. Furthermore toolholder set up time can be substantially reduced with corresponding reduction in down time of the machine. These and other practical advantages will be apparent from the following description.

Accordingly, the present invention provides a compact assembly oftoolholders in which each toolholder is formed so as to enable at least one cutting insert ofthe removably mounted type to be locatingly received by the toolholder in order to provide a high strength cutting action and whereby each insert can be readily and quickly reset or replaced usually without removal of the toolholder from its position of use.

Close positioning of the cutting inserts is also made possible for their close proximity machining of a small workpiece.

In the usual manner each removable insert is preferably screw mounted in a locating recess in its toolholder.

One toolholder may receive accommodated or interfitting therein a further toolholder in a compact assembly. They may also be arranged for their relative linear adjustment such as by screw means whilst provision may be further included for their relative lateral spacing apart.

In the practical application of the invention reference is made to by way of example to the accompanying drawings in which: Figure 1 is a perspective view of a pair of toolholder assemblies in a typical relative position of use; Figure 2 is a plan view of the toolholder assemblies shown in the course of machining a workpiece, and Figure 3 is a detail face view of a spacing piece.

Each toolholder assembly 1 is shown comprising a main toolholder 2 receiving a further or sub toolholder 3, the body 20 of the main toolholder being clamped at 40 on a mounting block 4 which in turn is mounted on the machine slide assembly. The latter is not shown but directions of slide movement are indicated in Figure 2 as later referred to. Each main toolholder 2 has a pin 11 extending outwardly from it. A pin 11 may be pulled to enable the main toolholder 2 to be pulled out of the mounting block 4.

Each main toolholder body or shank 20 is formed with a longitudinal recess or pocket 22 which accommodates the shank 30 of the sub toolholder 3 secured therein by transverse screws 5 passing through slots 35 in the sub toolholder shank 30. Such mounting permits linear adjustment of the sub toolholder 3 relative to the main toolholder 2 by an adjustment screw 6 shown threaded in the rear end ofthe sub toolholder shank 30 with its head abutting the rear closed end 26 of the pocket 22 in the main toolholder shank 20.

Setting up of the toolholder assembly is also facilitated by location of the main toolholder shank 20 against the mounting block 4 such as by the step 24.

Each toolholder shank 20, 30 receives a removable cutting insert 7 of hard material such as tungsten carbide shown of the usual rhombic shape in face view and secured and located in a recess 27 or 37 of corresponding form at the forward or operative end of the shank 20 or 30 by a central screw 8.

Dependent on machining requirements appropriate corners of the insert 7 each provide a cutting tip 70. On tip wear the insert 7 can be reset or indexed to bring a further tip into position of use i.e. by temporarily slackening'or removing the screw 8. On full tip wear the insert is replaced.

The close positioning of the tool shanks 20, 30 enables such cutting inserts 7 to be employed in close proximity about a small workpiece such as the head of the stud S shown in Figure 2. Some offset ofthe forward end ofthe right hand shank 30 further assists close spacing of the adjacent inserts 7. The stud or other component is usually formed from bar stock coaxially fed through the machine spindle and parted off from the bar on completion of the machining cycle. Simultaneous machining of the workpiece by the inserts 7, or in rapid succession can be obtained.

In addition to the manner in which the inserts 7 can be readily and quickly reset or replaced with minimal machine down time, the located insert 7 and rigid shank assembly 20, 30 provides a much stronger cutting tip arrangement capable of withstanding significantly higher machine spindle speeds e.g. of the order of 2500 rpm. Thus surface machining speeds in the region of 40 metres per minute can be achieved resulting in a machining cycle as little as 3.5 seconds per workpiece as against a cycle of 36 seconds previously entailed. These and other figures quoted above are given by way of example only and may be varied according to requirements.

Whereas closest possible lateral positioning of the toolholder shanks is usually required for close proximity of the cutting tips 70, in some instances a degree of lateral spacing apart is required and is shown achieved by a spacing piece or strip 9 of suitable thickness (Figure 3) inserted and clamped between the shanks 20, 30. Elongated holes 95 in the spacer permit passage of the screws 5 and facilitate relative linear adjustment of the shanks 20, 30.

However plain circular holes may be provided in the spacer 9 locating about the screws 5 for relative sliding adjustment of the shank 30.

In the example shown in the drawings two toolholder assemblies 1 each providing a pair of cutting tips 70, are arranged in an opposed manner at opposite sides of the workpiece S. The left hand inserts 7 are shown lowermost and the right hand inserts uppermost i.e. in accordance with the usual clockwise direction of rotation of the workpiece by the machine spindle. However the number and arrangement of the assemblies and inserts may be varied according to requirements.

Front and rear slide movements of the machine are indicated by the arrows F and R in Figure 2.

It is to be understood that various developments or modifications ofthe toolholder assemblies described above may be made within the scope of the invention herein defined.

Claims (12)

1 A toolholder assembly wherein a compact assembly of toolholders is provided in which each toolholder is formed so as to enable at least one cutting insert of the removably mounted type to be locatingly received by the toolholder in order to provide a high strength cutting action and whereby the or each insert can be readily and quickly reset or replaced usually without removal of the toolholder from the assembly, the compact assembly of toolholders enabling close positioning of the cutting inserts to be provided for their close proximity machining of a workpiece especially a small workpiece.

2 A toolholder assembly according to claim 1 wherein a main toolholder receives accommodated or interfitting therein a further or sub toolholder in providing the compact assembly of the toolholders for close positioning of their respective cutting inserts.

3 A toolholder assembly according to claim 2 wherein the main toolholder is formed with a longitudinal recess or pocket which accommodates a shank of the sub toolholder.

4 A toolholder assembly according to claim 2 or 3 wherin the sub toolholder is linearly adjustable relative to the main toolholder.

5 A toolholder assembly according to claim 4 wherein linear adjustment of the sub toolholder relative to the main toolholder is effected by screw means acting between rear end parts of the toolholders.

6 A toolholder assembly according to any of the preceding claims wherein the toolholders are secured or clamped together by transverse screw means.

7 A toolholder assembly according to claims 4 and 6 or 5 and 6 wherein the transverse screw means permits said linear adjustment of the sub toolholder relative to the main toolholder.

8 A toolholder assembly according to any of the preceding claims 2 to 7 wherein the main toolholder is received in use by a mounting block for mounting in a machine tool such as on a slide assembly of the latter.

9 A toolholder assembly according to claim 8 wherein the main toolholder is adapted to be located for setting up purposes relative to the mounting block such as by step formation of said toolholder.

10 A toolholder assembly according to any of the preceding claims 2 to 9 wherein the rear of the main toolholder is provided with means such as a rearwardly extending pin to facilitate withdrawal of said toolholder (and the sub toolholder assembled therewith) from its position of use.

11 A tool holder assembly according to any of the preceding claims wherein a spacing piece or strip is provided for insertion between shanks ofthe toolholders in effecting lateral spacing apart of the latter as and when required.

12 A toolholder assembly when substantially as herein described with reference to the accompanying drawings.