GB2157991A

GB2157991A - Rotary cutting tool

Info

Publication number: GB2157991A
Application number: GB08411424A
Authority: GB
Inventors: John Howell
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-05-03
Filing date: 1984-05-03
Publication date: 1985-11-06
Also published as: GB8411424D0; GB2157991B

Abstract

This invention relates to rotary cutting tools, which are held in a chuck when in operation. Chucks commonly used in the art are threaded to accept a tool with a threaded shank which allows the tool to be firmly secured. The threading of tools formed from a single piece of steel is readily achieved and presents no problem. However, for some operations tungsten carbide is required as the cutting material. This material is difficult and expensive to machine. The rotary cutting tool of this invention comprises a two piece construction of a tungsten carbide shank 3 provided with cutting flutes 4 at its working end and secured (e.g. by brazing) to a rear end 1 of machined steel which may be threaded to cooperate with a threaded chuck. <IMAGE>

Description

SPECIFICATION Rotary cutting tools This invention relates to rotary cutting tools, in particular rotary cutting tools which are held in a chuck when in operation.

The function of the chuck is to fit the spindle drive of a machine tool and to grip the rear shank of the tool which is presented to the workpiece.

One kind of chuck in common use is the Clarkson autoclock chuck. This is designed to accept a tool with a threaded shank. The chuck possesses a split collet into which the rear shank of the tool is inserted. The split collet is then tightened by means of a spanner acting on a locking nut. The locking nut acts on a taper and squeezes the collet onto the shank. In this way the tool is rotated with the chuck when the latter is driven. The autolock chuck attempts to overcome the problem of slipping between the collect and the tool by using an internally threaded collet, and threads of which engage with corresponding external threading at the base of the tool shank. As a result, in the event of the tool twisting in relation to the collet, the tool will screw into the collet still further until it is sufficiently tight against the nut.

The most commonly used tools for use with such autoclock chucks are formed from a single piece of "high speed" steel which has a thread ground or cut into the shank.

However, there is a trend in the artto use tungsten carbide instead as it is a superior cutting material.

Unfortunately, tungsten carbide is so hard that it is difficult and expensive to thread.

We have now unexpectedly found that the major forces created by the collet of an autolock chuck on the tool shank are compression and torque forces.

We have, therefore, discovered that a two-piece construction which takes advantage of the respective qualities of steel and tungsten carbide is practicable for use in an autolock chuck. In particular a steel part can be used for the rear shank end because it is easily threaded whilst the remainder including the cutting end can be made of tungsten carbide. The two can be joined by a single joint, for example a brazed joint. Surprisingly, such as joint has been found able to resist successfully the stresses acting upon it.

Accordingly, the present invention provides a rotary cutting tool comprising a solid tungsten carbide shank provided with cutting flutes at its working end and having a rear end composed of steel machined to provide means for co-operating with a chuck, said rear end being attached to the tungsten carbide shank.

Further the present invention also provides a rotary cutting tool comprising a solid tungsten carbide shank provided with cutting flutes at its working end and having a rear end composed of steel machined to provide threads to co-operate with a threaded chuck, said rear end being attached to the tungsten carbide shank.

The rear end of machined steel may be attached to the tungsten carbide shank by a brazed joint. The brazed joint may be a butt braze or it may be achieved by brazing on a spigot or cone.

The rear end of machined steel may be centered thereby aligning the tool in the required position within the chuck.

The advantage of the rotary cutting tool of this invention is that it allows the shank of the cutting portion to be in one piece with the working cutter edges giving greater strength than the conventionally tipped tungsten carbide cutters.

One embodiment of the present invention will now be described by way of example oniy with reference to the accompanying drawings in which: Figure 1 is an elevation of a rotary cutting tool according to this invention.

Figure 2 is a corresponding perspective view of a rotary cutting tool according to this invention and a conventional chuck body cut away to show the location of the rotary cutting tool in an operational mode.

The rotary cutting tool illustrated comprises a solid tungsten carbide shank 3 provided with cutting flutes 4. The shank 3 is attached to a threaded rear end 1 composed of machined steel by means of a brazed joint 2.

In operation, the rotary cutting tool shown in Figure 1 is inserted into the split collet 5 of a conventional chuck 6 of appropriate size and is screwed into the co-operating threads 7 of the collet 5 until it becomes tight. The split collet 5 is then tightened by means of a spanner and is forced outwards towards a locking nut which causes it to act on the taper of the shank 3 of the rotary cutting tool. This action squeezes the sides of the collet 5 onto the shank 3 of the rotary cutting tool so compressing the shank 3 against the base of the collet 8 and holding it firmly in position.

The steel part and the tungsten carbide shank may be joined together by brazing or other means which will be apparent to those skilled in the art.

It will also be apparent to the man skilled in the art that various types of cutting flutes may be used in the present invention. The rotary cutting tool may be used, for example in end milling, sidemilling, boring, counterboring, or countersinking operations.

1. A rotary cutting tool comprising a tungsten carbide shank provided with cutting flutes at its working end and having a rear end composed of steel machined to provide means for co-operating with a chuck, said rear end being attached to the tungsten carbide shank.

2. A rotary cutting tool comprising a solid tungsten carbide shank provided with cutting flutes at its working end and having a rear end composed of steel machined to provide threads to co-operate with a threaded chuck, said rear end being attached to the tungsten carbide shank.

3. A rotary cutting tool according to claim 1 or 2 wherein said tungsten carbide shank is attached to said rear end by a brazed joint.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Rotary cutting tools This invention relates to rotary cutting tools, in particular rotary cutting tools which are held in a chuck when in operation. The function of the chuck is to fit the spindle drive of a machine tool and to grip the rear shank of the tool which is presented to the workpiece. One kind of chuck in common use is the Clarkson autoclock chuck. This is designed to accept a tool with a threaded shank. The chuck possesses a split collet into which the rear shank of the tool is inserted. The split collet is then tightened by means of a spanner acting on a locking nut. The locking nut acts on a taper and squeezes the collet onto the shank. In this way the tool is rotated with the chuck when the latter is driven. The autolock chuck attempts to overcome the problem of slipping between the collect and the tool by using an internally threaded collet, and threads of which engage with corresponding external threading at the base of the tool shank. As a result, in the event of the tool twisting in relation to the collet, the tool will screw into the collet still further until it is sufficiently tight against the nut. The most commonly used tools for use with such autoclock chucks are formed from a single piece of "high speed" steel which has a thread ground or cut into the shank. However, there is a trend in the artto use tungsten carbide instead as it is a superior cutting material. Unfortunately, tungsten carbide is so hard that it is difficult and expensive to thread. We have now unexpectedly found that the major forces created by the collet of an autolock chuck on the tool shank are compression and torque forces. We have, therefore, discovered that a two-piece construction which takes advantage of the respective qualities of steel and tungsten carbide is practicable for use in an autolock chuck. In particular a steel part can be used for the rear shank end because it is easily threaded whilst the remainder including the cutting end can be made of tungsten carbide. The two can be joined by a single joint, for example a brazed joint. Surprisingly, such as joint has been found able to resist successfully the stresses acting upon it. Accordingly, the present invention provides a rotary cutting tool comprising a solid tungsten carbide shank provided with cutting flutes at its working end and having a rear end composed of steel machined to provide means for co-operating with a chuck, said rear end being attached to the tungsten carbide shank. Further the present invention also provides a rotary cutting tool comprising a solid tungsten carbide shank provided with cutting flutes at its working end and having a rear end composed of steel machined to provide threads to co-operate with a threaded chuck, said rear end being attached to the tungsten carbide shank. The rear end of machined steel may be attached to the tungsten carbide shank by a brazed joint. The brazed joint may be a butt braze or it may be achieved by brazing on a spigot or cone. The rear end of machined steel may be centered thereby aligning the tool in the required position within the chuck. The advantage of the rotary cutting tool of this invention is that it allows the shank of the cutting portion to be in one piece with the working cutter edges giving greater strength than the conventionally tipped tungsten carbide cutters. One embodiment of the present invention will now be described by way of example oniy with reference to the accompanying drawings in which: Figure 1 is an elevation of a rotary cutting tool according to this invention. Figure 2 is a corresponding perspective view of a rotary cutting tool according to this invention and a conventional chuck body cut away to show the location of the rotary cutting tool in an operational mode. The rotary cutting tool illustrated comprises a solid tungsten carbide shank 3 provided with cutting flutes 4. The shank 3 is attached to a threaded rear end 1 composed of machined steel by means of a brazed joint 2. In operation, the rotary cutting tool shown in Figure 1 is inserted into the split collet 5 of a conventional chuck 6 of appropriate size and is screwed into the co-operating threads 7 of the collet 5 until it becomes tight. The split collet 5 is then tightened by means of a spanner and is forced outwards towards a locking nut which causes it to act on the taper of the shank 3 of the rotary cutting tool. This action squeezes the sides of the collet 5 onto the shank 3 of the rotary cutting tool so compressing the shank 3 against the base of the collet 8 and holding it firmly in position. The steel part and the tungsten carbide shank may be joined together by brazing or other means which will be apparent to those skilled in the art. It will also be apparent to the man skilled in the art that various types of cutting flutes may be used in the present invention. The rotary cutting tool may be used, for example in end milling, sidemilling, boring, counterboring, or countersinking operations. CLAIMS

4. A rotary cutting tool according to claim 3 wherein said brazed joint is a butt braze.

5. A rotary cutting tool substantially as hereinbefore described with reference to Figs. 1 and 2 of the accompanying drawings.

5. A rotary cutting tool according to claim 3 wherein said brazed joint is formed by brazing on a spigot or a cone.

Amendments to the claims have been filed, and have the following effect: (a) Claims 1 and 2 above have been deleted or textually amended.

(b) New or textually amended claims ahve been filed as follow: (c) Claims 3,4 and 5 above have been re-numbered as 2,3 and 4.

1.A A rotary cutting tool having a shank and a fluted cutting end composed of an integral part of tungsten carbide and a steel slug attached to the end of the shank remote from said cutting end of the tool and threaded at its free end to cooperate with the thread of a standard milling machine chuck collet, the threaded engagement between the tool and the collet allowing the collet to tighten upon and grip the tool shank more firmly in the event of any slippage in the drive between the chuck and the tool, thereby ensuring a firm driving engagement therebetween.