GB2049504A

GB2049504A - Lathe chuck

Info

Publication number: GB2049504A
Application number: GB7918477A
Authority: GB
Original assignee: Meyrick N C
Current assignee: Meyrick N C
Priority date: 1979-05-25
Filing date: 1979-05-25
Publication date: 1980-12-31

Abstract

A lathe chuck, particularly for use on a wood-turning lathe, comprises a shaft portion 10, for mounting on the work spindle of the lathe, formed at one end thereof with a socket portion 11 formed with an open mouthed frusto- conical socket 12 which is coaxial with the shaft portion and tapers inwardly as it extends from the open mouth thereof towards the shaft portion. In use, the end of the workpiece is received and retained frictionally within the socket 12. <IMAGE>

Description

SPECIFICATION Improvements in lathe chucks The invention relates to lathe chucks and particularly but not exclusively to a chuck suitable for use on a wood-turning lathe.

Hitherto, chucks for use on wood-turning lathes have usually comprised a driving centre comprising a shaft portion for mounting on the work spindle of the lathe and formed at the end thereof with two or more sharp axially projecting lugs designed to bite into the end of the workpiece. Such driving centres have a number of severe disadvantages.

For example, there is the danger that a hand-held lathe tool will accidentally be brought into contact with the driving centre, causing the tool to be swept out of the user's hand or at least to be damaged.

Similarly, if the piece of wood being turned breaks or becomes jammed against rotation the driving centre can cause the wood to splinter and to be thrown off the lathe. Also, when a long bore is being formed axially along a workpiece being held by the driving centre, there is a risk of the boring tool being moved axially too far so that it engages the driving centre causing damage to the driving centre and/or to the tool. The shape of the driving centre is also such that it may cause injury if inadvertently touched, and it may also seize and draw in a trailing item of clothing such as a necktie.

The above-mentioned occurrences are particularly likely to occur where the lathe is being used by an unskilled operator, such as is often the situation in schools. The invention therefore sets out to provide an improved form of lathe chuck which is particularly suitable for use in schools but which also has such advantages as to render it suitable for more general application.

According to the invention there is provided a lathe chuck comprising a shaft portion, for mounting on the work spindle of a lathe, formed at one end thereof with a socket portion formed with an open mouthed socket which is coaxial with the shaft portion and tapers inwardly as it extends from the open mouth thereof towards the shaft portion.

The open mouthed socket is preferably frustoconical. The external periphery of the socket portion is preferably circular in cross section. For example, it may be cylindrical.

The shaft portion of the chuck may be formed with a morse taper, in known manner, and in this case the taper angle of the socket is preferably greater than that of the morse taper. For example the internal surface of the socket may taper at substantially 200 with respect to the longitudinal axis of the chuck.

The following is a more detailed description of one embodiment of the invention reference being made to the accompanying drawings in which: Figure 1 is a longitudinal section through one form of chuck in accordance with the invention, and Figure 2 is an end view of the chuck looking from the left of Figure 1.

The lathe chuck shown in the drawing comprises a shaft portion 10 formed with a No.3 morse taper for fitting to the work spindle of a wood-turning lathe in well known manner.

At the larger diameter end of the shaft portion 10 there is formed a socket portion 11 having a circular cylindrical external periphery and formed with an open mouthed socket 12 the inner surface 13 ofwhich is frusto-conical in shape. The internal -surface of the frusto-conical socket tapers at Sûo withrrespect to the longitudinal axis ofthechuck.

The chuck may conveniently be turned-from any suitable material such as aluminium, duralumin or mild steel. in-the example shown there is a flat annular shoulder 14 between the shaft portion 10 and the socket portion 11, but in an alternative arrangement the shoulder may be tapered so as to provide a thicker body of metal between the shoulder and the interior surface of the socket 12.

In use, the shaft portion of the chuck is mounted on the work spindle of theiathe in the norman manner of driving centres incorporating a morse taper. One end of the workpiece is inserted in the socket 12 and the tailstock of the lathe is then tightened up to press the end of the workpiece firmly into the socket where it is automatically centred due to the tapered shape of the socket. It is foundvthat in use there-is-sufficient friction between the workpiece and the frusto-conical surface 13 to impart sufficient drive to the workpice. This frictional engagement may be varied by adjusting the tailstock. It is necessary that the taper on the internal surface of the socket should be greater than the morse taper so that if slipping does occur it occurs first between the workpiece and the socket.

The 200 taper of the socket is only a preferred dimension and other angles of taper may be suitable depending on the material of the chuck and the material of the workpiece. It will, however, generally be found that a taper within the range of 150 to 300 will be appropriate.

It will be appreciated that since the chuck has a simple cylindrical external surface there are no protrusions, keys or sharp edges to cause injury or to be fouled. Due to the self-centring action of the chuck it is possible to remove the workpiece from the chuck and then replace it with automatic exact centring.

If the lathe tool should happen to come into engagement with the chuck, damage to the tool will be a minimum since there are no protruding edges on the chuck. Should a tool jam in the workpiece, or the workpiece otherwise be restrained from rotation, it will simply slip relative to the chuck without risk of splintering or breakage, or of being thrown from the lathe.

If a long bore is being made axially along a workpiece little damage will be done to the chuck or boring tool if the bore should be taken so far as to engage the flat bottom of the socket.

1. A lathe chuck comprising a shaft portion, for mounting on the work spindle of a lathe, formed at one end thereof with a socket portion formed with an open mouthed socket which is coaxial with the shaft portion and tapers inwardly as it extends from the

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in lathe chucks The invention relates to lathe chucks and particularly but not exclusively to a chuck suitable for use on a wood-turning lathe. Hitherto, chucks for use on wood-turning lathes have usually comprised a driving centre comprising a shaft portion for mounting on the work spindle of the lathe and formed at the end thereof with two or more sharp axially projecting lugs designed to bite into the end of the workpiece. Such driving centres have a number of severe disadvantages. For example, there is the danger that a hand-held lathe tool will accidentally be brought into contact with the driving centre, causing the tool to be swept out of the user's hand or at least to be damaged. Similarly, if the piece of wood being turned breaks or becomes jammed against rotation the driving centre can cause the wood to splinter and to be thrown off the lathe. Also, when a long bore is being formed axially along a workpiece being held by the driving centre, there is a risk of the boring tool being moved axially too far so that it engages the driving centre causing damage to the driving centre and/or to the tool. The shape of the driving centre is also such that it may cause injury if inadvertently touched, and it may also seize and draw in a trailing item of clothing such as a necktie. The above-mentioned occurrences are particularly likely to occur where the lathe is being used by an unskilled operator, such as is often the situation in schools. The invention therefore sets out to provide an improved form of lathe chuck which is particularly suitable for use in schools but which also has such advantages as to render it suitable for more general application. According to the invention there is provided a lathe chuck comprising a shaft portion, for mounting on the work spindle of a lathe, formed at one end thereof with a socket portion formed with an open mouthed socket which is coaxial with the shaft portion and tapers inwardly as it extends from the open mouth thereof towards the shaft portion. The open mouthed socket is preferably frustoconical. The external periphery of the socket portion is preferably circular in cross section. For example, it may be cylindrical. The shaft portion of the chuck may be formed with a morse taper, in known manner, and in this case the taper angle of the socket is preferably greater than that of the morse taper. For example the internal surface of the socket may taper at substantially 200 with respect to the longitudinal axis of the chuck. The following is a more detailed description of one embodiment of the invention reference being made to the accompanying drawings in which: Figure 1 is a longitudinal section through one form of chuck in accordance with the invention, and Figure 2 is an end view of the chuck looking from the left of Figure 1. The lathe chuck shown in the drawing comprises a shaft portion 10 formed with a No.3 morse taper for fitting to the work spindle of a wood-turning lathe in well known manner. At the larger diameter end of the shaft portion 10 there is formed a socket portion 11 having a circular cylindrical external periphery and formed with an open mouthed socket 12 the inner surface 13 ofwhich is frusto-conical in shape. The internal -surface of the frusto-conical socket tapers at Sûo withrrespect to the longitudinal axis ofthechuck. The chuck may conveniently be turned-from any suitable material such as aluminium, duralumin or mild steel. in-the example shown there is a flat annular shoulder 14 between the shaft portion 10 and the socket portion 11, but in an alternative arrangement the shoulder may be tapered so as to provide a thicker body of metal between the shoulder and the interior surface of the socket 12. In use, the shaft portion of the chuck is mounted on the work spindle of theiathe in the norman manner of driving centres incorporating a morse taper. One end of the workpiece is inserted in the socket 12 and the tailstock of the lathe is then tightened up to press the end of the workpiece firmly into the socket where it is automatically centred due to the tapered shape of the socket. It is foundvthat in use there-is-sufficient friction between the workpiece and the frusto-conical surface 13 to impart sufficient drive to the workpice. This frictional engagement may be varied by adjusting the tailstock. It is necessary that the taper on the internal surface of the socket should be greater than the morse taper so that if slipping does occur it occurs first between the workpiece and the socket. The 200 taper of the socket is only a preferred dimension and other angles of taper may be suitable depending on the material of the chuck and the material of the workpiece. It will, however, generally be found that a taper within the range of 150 to 300 will be appropriate. It will be appreciated that since the chuck has a simple cylindrical external surface there are no protrusions, keys or sharp edges to cause injury or to be fouled. Due to the self-centring action of the chuck it is possible to remove the workpiece from the chuck and then replace it with automatic exact centring. If the lathe tool should happen to come into engagement with the chuck, damage to the tool will be a minimum since there are no protruding edges on the chuck. Should a tool jam in the workpiece, or the workpiece otherwise be restrained from rotation, it will simply slip relative to the chuck without risk of splintering or breakage, or of being thrown from the lathe. If a long bore is being made axially along a workpiece little damage will be done to the chuck or boring tool if the bore should be taken so far as to engage the flat bottom of the socket. CLAIMS

1. A lathe chuck comprising a shaft portion, for mounting on the work spindle of a lathe, formed at one end thereof with a socket portion formed with an open mouthed socket which is coaxial with the shaft portion and tapers inwardly as it extends from the open mouth thereof towards the shaft portion.

2. A lathe chuck according to claim 1, wherein the open mouthed socket is frusto-conical.

3. A lathe chuck according to claim 1 or claim 2, wherein the external periphery of the socket portion is circular in cross section.

4. A lathe chuck according to claim 3, wherein the external periphery of the socket portion is cylindrical.

5. A lathe chuck according to any of the preceding claims wherein the shaft portion of the chuck is formed with a morse taper

6. A lathe chuck according to claim 5, wherein the taper angle of the socket is greater than that of the morse taper.

7. A lathe chuck according to any of the preceding claims, wherein the internal surface of the socket tapers at substantially 200 with respect to the longitudinal axis of the chuck.

8. A lathe chuck substantially as hereinbefore described with reference to the accompanying drawings.