GB2048132A - Tools for cutting internal threads - Google Patents

Abstract

A lathe tool comprising a shank 2 which, in cutting a thread in a cylindrical bore, can lie with its length parallel to the axis of the bore, a head 6 pivoted to the shank about a second axis A-A, perpendicular to the length of the shank, a cutting insert 24 clamped to the head and means for adjusting and locking the angular position of the head 6 around the second axis, so that a cutting tip 22 of the insert can be set in an attitude related to the helix angle of the thread to be cut. <IMAGE>

Description

SPECIFICATION Tools for cutting internal threads This invention relates to tools to be mounted on a lathe or other machine tool, for use in cutting an internal screw thread in a workpiece, by means of a single cutting tip.

Hitherto, lathe tools for use in cutting an internal screw thread have embodied an insert of tool material shaped to include the cutting tip, this insert being fixed in position relatively to a shank, the shank being then mounted on the carriage of a lathe. Such a tool can only be used for a small range of helix angle of thread. Any attempt to use it outside this range will lead to the thread being damaged by the trailing portion of the cutting tip.

According to the present invention a lathe tool comprises a shank which, in cutting a thread in a cylindrical bore, can lie with its length parallel to the axis of the -bore, a head pivoted to the shank about a second axis, perpendicular to the length of the shank, a clamp for securing to the head an insert of tool material shaped to include the cutting tip, and means for adjusting and locking the angular position of the head around the second axis, so that the tip can be set in an attitude related to the helix angle of the thread to be cut.

The invention will be understood more clearly from the following description of one example of a tool embodying the invention. This example is illustrated by the accompanying drawings in which: Figure 1 is a view of the head of the tool, looking along the length of the shank; Figure 2 is a side elevation, looking in the direction of the arrow II in Figure 1; and Figure 3 is a view from below, looking in the diection of the arrow Ill in Figure 1.

The shank 2 is essentially a bar of cylindrical shape, with four flat side faces 4. In one side of the leading end of the shank there is a recess to accommodate the head 6. The head is pivoted to the shank about an axis A-A, the pivot being defined by a screw 8, which cooperates with a clearance bore in the portion 10 of the shank alongside the head 6, and with a threaded bore in the head 6. When the angular position of the head 6 is to be adjusted, the screw 8 can be slightly loosened, by means of a key inserted into its head 12, and after adjustment the screw 8 is tightened again.

The adjustment is performed by two grub screws 14 and 16, which cooperate with a threaded bore in the head 6, and the inner ends of which engage a pin 18 fixed in the portion 10 of the shank. There is a recess 20 in the head to accommodate the pin 18 throughout the desired range of angular movement of the head.

The cutting tip 22 is on an insert 24 of tool material, which is essentially a bar of trapezium cross section (as can be seen in Figure 2). This bar engages in a corresponding recess in the end of the head 6, and is clamped by a trapezium-shaped component 26 through which a screw 28 passes into a threaded bore 30 in the head 6.

In Figure 2 the head is shown in a neutral position, in which the cutting tip 22 is in a position suited to cutting a groove having zero helix angle.

In order to prepare the tool for cutting an internal screw thread, the head 6 is rotated (clockwise or anticlockwise as seen in Figure 2, according to whether the thread is left-hand or right-hand), through an angle equal to the helix angle of the thread to be cut.

This adjustment can be facilitated by supplying a key for turning the grub screws 14, 16, this key carrying a disc which is calibrated to indicate the angular movement of the head 6 produced by a given rotation of the grub screws.

1. A lathe tool comprising a shank which, in cutting a thread in a cylindrical bore, can lie with its length parallel to the axis of the bore, a head pivoted to the shank about a second axis, perpendicular to the length of the shank, a clamp for securing to the head an insert of tool material shaped to include the cutting tip, and means for adjusting and locking the angular position of the head around the second axis, so that the tip can be set in an attitude related to the helix angle of the thread to be cut.

2. A tool according to claim 1, in which the shank is a bar, in one side of the leading end of the shank there is a recess to accommodate the head, and the head is pivoted to the shank about a screw.

3. A tool according to claim 2, in which the adjustment is performed by two grub screws, which cooperate with a threaded bore in the head, and the inner ends of which engage a pin fixed in the shank, and the locking is performed by tightening the screw mentioned in claim 2.

4. A tool according to claim 1, substantially as described with reference to the accompanying drawings.

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

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Tools for cutting internal threads This invention relates to tools to be mounted on a lathe or other machine tool, for use in cutting an internal screw thread in a workpiece, by means of a single cutting tip. Hitherto, lathe tools for use in cutting an internal screw thread have embodied an insert of tool material shaped to include the cutting tip, this insert being fixed in position relatively to a shank, the shank being then mounted on the carriage of a lathe. Such a tool can only be used for a small range of helix angle of thread. Any attempt to use it outside this range will lead to the thread being damaged by the trailing portion of the cutting tip. According to the present invention a lathe tool comprises a shank which, in cutting a thread in a cylindrical bore, can lie with its length parallel to the axis of the -bore, a head pivoted to the shank about a second axis, perpendicular to the length of the shank, a clamp for securing to the head an insert of tool material shaped to include the cutting tip, and means for adjusting and locking the angular position of the head around the second axis, so that the tip can be set in an attitude related to the helix angle of the thread to be cut. The invention will be understood more clearly from the following description of one example of a tool embodying the invention. This example is illustrated by the accompanying drawings in which: Figure 1 is a view of the head of the tool, looking along the length of the shank; Figure 2 is a side elevation, looking in the direction of the arrow II in Figure 1; and Figure 3 is a view from below, looking in the diection of the arrow Ill in Figure 1. The shank 2 is essentially a bar of cylindrical shape, with four flat side faces 4. In one side of the leading end of the shank there is a recess to accommodate the head 6. The head is pivoted to the shank about an axis A-A, the pivot being defined by a screw 8, which cooperates with a clearance bore in the portion 10 of the shank alongside the head 6, and with a threaded bore in the head 6. When the angular position of the head 6 is to be adjusted, the screw 8 can be slightly loosened, by means of a key inserted into its head 12, and after adjustment the screw 8 is tightened again. The adjustment is performed by two grub screws 14 and 16, which cooperate with a threaded bore in the head 6, and the inner ends of which engage a pin 18 fixed in the portion 10 of the shank. There is a recess 20 in the head to accommodate the pin 18 throughout the desired range of angular movement of the head. The cutting tip 22 is on an insert 24 of tool material, which is essentially a bar of trapezium cross section (as can be seen in Figure 2). This bar engages in a corresponding recess in the end of the head 6, and is clamped by a trapezium-shaped component 26 through which a screw 28 passes into a threaded bore 30 in the head 6. In Figure 2 the head is shown in a neutral position, in which the cutting tip 22 is in a position suited to cutting a groove having zero helix angle. In order to prepare the tool for cutting an internal screw thread, the head 6 is rotated (clockwise or anticlockwise as seen in Figure 2, according to whether the thread is left-hand or right-hand), through an angle equal to the helix angle of the thread to be cut. This adjustment can be facilitated by supplying a key for turning the grub screws 14, 16, this key carrying a disc which is calibrated to indicate the angular movement of the head 6 produced by a given rotation of the grub screws. CLAIMS

1. A lathe tool comprising a shank which, in cutting a thread in a cylindrical bore, can lie with its length parallel to the axis of the bore, a head pivoted to the shank about a second axis, perpendicular to the length of the shank, a clamp for securing to the head an insert of tool material shaped to include the cutting tip, and means for adjusting and locking the angular position of the head around the second axis, so that the tip can be set in an attitude related to the helix angle of the thread to be cut.

2. A tool according to claim 1, in which the shank is a bar, in one side of the leading end of the shank there is a recess to accommodate the head, and the head is pivoted to the shank about a screw.

3. A tool according to claim 2, in which the adjustment is performed by two grub screws, which cooperate with a threaded bore in the head, and the inner ends of which engage a pin fixed in the shank, and the locking is performed by tightening the screw mentioned in claim 2.

4. A tool according to claim 1, substantially as described with reference to the accompanying drawings.