GB1594759A

GB1594759A - Recess facing tool

Info

Publication number: GB1594759A
Application number: GB2522878A
Authority: GB
Original assignee: Estra Normteile & Masch
Current assignee: Estra Normteile & Masch
Priority date: 1977-06-14
Filing date: 1978-05-31
Publication date: 1981-08-05
Also published as: FR2394351B1; DE2726734C2; FR2394351A1; DE2726734A1; BE867797A

Description

(54) RECESS FACING TOOL (71) We, ESTRA NORMTEILE & MAS CHINEN GmbH, a German body corporate, of Veldensteinstrasse 2, 8 Munich 60, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described, in and by the following statement:- This invention relates to a recess facing tool with a cutting body carrier which is fixed to the side of a chuck shaft or made in one piece with it, and a longitudinally slidable clamping finger mounted on the cutting body carrier.

A recess facing tool is known in which a clamping leaf is clamped down by a superimposed claw by means of a wedge arrangement. In other words, the clamping leaf is non-positively immobilized against the chuck shaft. The clamping leaf is seated point-wise or line-wise with its rear end upon the cutting-body carrier. This provides only limited lateral stability. Owing to this it is, for instance, impossible to brace the clamping finger and the cutting-body carrier and to machine the cutting blade and the clampingleaf blade in the braced condition. The recess depth is also limited as a result of the lack of lateral stability.

Also known is a recess facing tool of voluminous construction wherein the cutting body is slidably mounted. Here the clamping finger is placed on the side in a groove parallel to the recess cutter on the base body, and on the other side, narrowly spaced, upon the recess cutter. This necessitates a very limited reserve of elasticity, and the recess cutter is very long as well. Clamping cannot be very exact, accordingly. Clamping may give way under load. If a large positive clamping angle is desired as well, the tool becomes unduly complicated.

What is desired is a recess facing tool which, besides having great lateral stability, makes it possible to carry out the final machining operations of the recess facing tool in the braced condition. This is important because, unlike most turning tools, in the case of recess facing tools the shaft must be narrower than the cutter. For this reason the possibility of joint grinding in the braced condition is of special interest.

The present invention provides a recess facing tool comprising a cutting-body carrier which is fixed to or integral with the side of a chuck shaft, an elongate clamping finger slidably mounted on the carrier, guide means for guiding the finger in the longitudinal direction, a clamping screw clamping the finger to the carrier, and a cutting body clamped between the front end of the finger and the carrier under the action of the clamping screw, the rear end of the finger having two support faces constituting the only two points at which the finger bears on the carrier under the action of the clamping screw.

The support surfaces preferably lie substantially in one plane with the cutting edge.

Guiding of the clamping finger without play Parallel to the cutting edge is of particu lar advantage. The guide may be formed as a key or an adjusting spring in a longitudinal groove in at least one of the mutually opposite faces of the clamping finger and the cutting body carrier. There may be two short keys, fitted into the respective ends of the groove.

The guide may, however, be given in the form of two bolts fitting into a longitudinal groove in the bearing face of the clamping finger, a flattened head of each fitting bolt sliding in the groove.

For adjusting the clamping finger there may advantageously be provided on the rear side of the clamping finger an adjustable screw whose head ears against a pin projecting from the chuck shaft.

According to the invention a method of machining the recess facing tool is possible, wherein the tool, after having been hardened, is finished in the braced condition; in particular the cutting blade and the blade of the clamping finger may be ground in the braced condition. The last-named step is unattainable with the known tools, as these ensure stability of the clamping finger at best in one direction only. Cutting-body carriers and clamping fingers may be given exceptionally large dimensions, and this with a comparatively small chuck shaft. More par ticularly, in automated lathes, where space is highly restricted, it is now possible to recess very deep grooves of small cross-section, which could not hitherto have been done by reason of the great lateral forces involved.

The clamping finger is preferably made relatively long. High stressing with reserve elasticity is made possible by spacing the clamping point far from the counter-bearing.

The cutting body is securely held even if the cutting body carrier plate is twisted or oscillated.

The adjustment of the cutting body after precision grinding may advantageously be effected by means of the above-mentioned screw screwed into the back of the clamping finger.

Foolproof lateral guidance can be achieved in the recess direction. The preferred connection by keys and grooves is such that, on the one hand, the clamping movement remains possible and, on the other, the tool is guided at right angles to it without play.

Thus there is a substantial improvement not only in the scaling work of the tool, but also in the production of the blade of the cutting-body carrier and the clamping finger blade in the braced condition. The cutting blade and the clamping finger can be made wider than hitherto in relation to the cutting body.

Owing to the strong pre-stressing that can be achieved, not only is the cutting body more securely held, but lateral deflection by the cutting stress is no longer as large as in the case of cutting-body carriers or clamping fin gers which have been finished unstressed (unbraced). The two-plane point support of the counter-bearing yields, in combination with the clamping point, a three-point support. Both parts can be finally machined with an inserted soft ancillary body instead of the cutting body.

The invention will be described further, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a recess facing tool in side elevation, as seen from the rear of the lathe; Figure 2 is a plan view of the tool; Figure 3 is a rear view of the tool, i.e. as seen from the headstock side of the lathe; Figure 4 is a front elevation of the tool, showing the cutter; Figure 5 is a view of the clamping finger in the division plane, in the direction 20-21 indicated in Figure 3; Figure 6 is a view of the cutting body carrier in the division plane, in the direction 30-31 indicated in Figure 3; Figure 7 shows another embodiment with a detail of the key in section along the line C-C in Figure 8; Figure 8 is a plan view of the embodiment shown in Figure 7; Figure 9 is a side elevation of another embodiment of a recess facing tool, the chuck shaft and the cutting-body carrier being made in one piece; Figure 10 is a plan view of the embodiment shown in Figure 9; and Figure 11 is a front elevation of the embodiment shown in Figure 7.

In general a chuck shaft is formed with a rectangular or round cross-section in accordance with the conventional accommodation of tools in lathes. The rectangular crosssection has been chosen for the chuck shaft 1 in the forms of embodiment illustrated.

According to a first embodiment a cutting-body carrier 2 is fixed to the side of the chuck shaft 1 by retaining screws 3 and is positioned by fitting pins 4. A curved cutting blade 6, which is formed in one piece with the cutting-body carrier 2 and carries a cutting body 7 in a V-shaped groove 5, is curved according to the diameter of the groove to be recesses. A clamping finger 8, which is clamped by means of a clamping screw 10, "stands" upon the cutting-body carrier 2 and clamps the cutting-body 7 at a clamping point 28. A screw 40, which is screwed into the clamping finger 8, is set against an oblique pin 42 in the chuck shaft 1 and, when the clamping screw 10 has been tightened up, is held immobilized by the pin 42. As will be seen in particular from Figures 2 and 3, in which a steel holding cassette is indicated at 111, the cutter is placed unusually close to the steel holding cassette, closer than in conventional recess facing tools, where the clamping finger is placed on a wall that is mostly part of the chuck shaft.

At its rear end the clamping finger 8 has two support points 22 and 23, constituted by the two separate faces which are inevitably formed by a central groove 26 (see especially Figure 5) running through the cutting-body carrier 2 and the clamping finger 8.

The point 24 at which the force of the clamping screw 10 is applied lies on a line connecting the support point 23 and the clamping point 28, so that the clamping force imparts no excessive twist to the clamping system. The cutting-body carrier 2 and the camping finger 8 are guided in the recessing direction by positive guide means on their sides facing each other. The position of the groove 26 in the clamping finger 8 and of the groove 27 in the cutting-body carrier 2 is clearly shown in Figures 5 and 6. In this form of embodiment, rectangular keys 125 and 126 are fitted into each end of the groove, in the present case tightly in the cutting-body carrier 2, enabling the clamping finger 8 to execute a movement in the recessing direction without lateral play, in order to allow adjustment of the cutting body 7 after precision grinding (polishing).

The wide spacing of the two support points 22 and 23 and the clamping point 28 (Figure 5) makes possible firm bracing with a reserve of elasticity. Owing to this, the cutting body 7 is held much more reliably than by a compact clamping finger, such as appears in the voluminous tool mentioned above. When the tool is made, the clamping finger 8 and the cutting-body carrier 2 are braced, a soft ancillary body being put between them instead of the cutting body, and then the contact surface (not shown) of the chuck shaft, as well as (Figure 4) the outer faces 13 and 14 (Figure 4) and the inner faces 15 and 16 of the curved cutting blade 6 and the clamping finger blade 9, can be finally machined or polished in the stressed (braced) condition. Here reference numeral 11 indicates the outside radius of the smallest possible groove and, 12 the inside radius of the large groove that can be recessed with the tool. It will be seen that the wider the range of recessable diameters is to be, the sooner must the cutting blade 6 run down into a point, which restricts the structural height.

Since the cutting blade and the clamping finger are to be as strong as possible, very little play is allowed at the groove wall.

Because the clamping finger stands upon the bod carrier, can braced together cutting carrier, can braced together with it finalry machined in the tion, only very slight deformations occur under load, because of this prestressing, so that this play (clearance) can be kept very small.

Owing to the prestressing, external cutting stress acting on the tool causes much less deformation than in other tools.

The use of extra hard materials, whose melting point lie close to their quenching temperature, for the cutting-body and the clamping finger, means that these parts do, however, tend to run appreciable out of true.

This is elucidated in Figure 8. To solve this problem, keys whose surfaces 46 are offset as shown in Figure 7, i.e. keys whose halves are offset relative to each other, are inserted into the grooves 26, 27. It is thus possible, by trying out variously offset keys, to find a mean relative position of the two parts, in which they can be finally machined in braced condition.

Figures 9 to 11 show a third form of embodiment, wherein the chuck shaft and the cutting-body carrier form a single part 50. The clamping finger 52 alone has a through-groove 58. Fitting bolts 54 and 56 are driven into the cutting-plate carrier. The fitting bolts are flattened on the side and thus provide good guiding in the clamping finger 52. The same parts as described above are indicated in the drawings by the same reference symbols, so that, to avoid overburdening the description, they will not be described again.

If the clamping finger 52 has been moved after the additional griding of the cutting body 7, then a screw 60 which has an eccentric head, is to be adjusted until it again fits tightly against the clamping finger 52.

WHAT WE CLAIM IS: 1. A recess facing tool comprising a cutting-body carrier which is fixed to or integral with the side of a chuck shaft, an elongate damping finger slidably mounted on the carrier, guide means for guiding the finger in the longitudinal direction, a clamping screw clamping the finger to the carrier, and a cutting body clamped between the front end of the finger and the carrier under the action of the clamping screw, the rear end of the finder having two support faces constituting the only two points at which the finger bears on the carrier under the action of the clamping screw.

2. A tool as claimed in claim 1, in which the support faces and the cutting edge of the cutting body are substantially coplanar.

3. A tool as claimed in claim 1 or 2, in which the clamping finger is longitudinally guided without play parallel to the cutting edge of the cutting body.

4. A tool as claimed in claim 3, in which the clamping finger is guided by a key or an adjusting spring within a longitudinal groove in at least one of the adjacent faces of the clamping finger and the cutting body carrier.

5. A tool as claimed in claim 4, in which a said key is accommodated in each end of the groove.

6. A tool as claimed in claim 5, in which the keys are constituted by bolts accommodated in a longitudinal groove in the clamping finger, a flattened head of each bolt sliding in the groove.

7. A tool as claimed in any preceding claim, in which the clamping screw is remote from the cutting body.

8. A tool as claimed in any preceding claim, in which, for adjusting the clamping finger longitudinally, the rear end of the clamping finger is provided with an adjustable screw whose head bears against a pin projecting from the chuck shaft.

9. A recess facing tool substantially as described herein with reference to, and as shown in, Figures 1 to 6, or Figures 9 to 11 of the accompanying drawings.

10. A method of finishing a recess facing tool according to any preceding claim, in which the tool is finally machined in the braced condition.

11. A method as claimed in claim 10, substantially as described herein.

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

Claims

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

22 and 23 and the clamping point 28 (Figure 5) makes possible firm bracing with a reserve of elasticity. Owing to this, the cutting body 7 is held much more reliably than by a compact clamping finger, such as appears in the voluminous tool mentioned above. When the tool is made, the clamping finger 8 and the cutting-body carrier 2 are braced, a soft ancillary body being put between them instead of the cutting body, and then the contact surface (not shown) of the chuck shaft, as well as (Figure 4) the outer faces 13 and 14 (Figure 4) and the inner faces 15 and 16 of the curved cutting blade 6 and the clamping finger blade 9, can be finally machined or polished in the stressed (braced) condition. Here reference numeral 11 indicates the outside radius of the smallest possible groove and, 12 the inside radius of the large groove that can be recessed with the tool. It will be seen that the wider the range of recessable diameters is to be, the sooner must the cutting blade 6 run down into a point, which restricts the structural height.

Since the cutting blade and the clamping finger are to be as strong as possible, very little play is allowed at the groove wall.

Because the clamping finger stands upon the bod carrier, can braced together cutting carrier, can braced together with it finalry machined in the tion, only very slight deformations occur under load, because of this prestressing, so that this play (clearance) can be kept very small.

Owing to the prestressing, external cutting stress acting on the tool causes much less deformation than in other tools.

The use of extra hard materials, whose melting point lie close to their quenching temperature, for the cutting-body and the clamping finger, means that these parts do, however, tend to run appreciable out of true.

This is elucidated in Figure 8. To solve this problem, keys whose surfaces 46 are offset as shown in Figure 7, i.e. keys whose halves are offset relative to each other, are inserted into the grooves 26, 27. It is thus possible, by trying out variously offset keys, to find a mean relative position of the two parts, in which they can be finally machined in braced condition.

Figures 9 to 11 show a third form of embodiment, wherein the chuck shaft and the cutting-body carrier form a single part 50. The clamping finger 52 alone has a through-groove 58. Fitting bolts 54 and 56 are driven into the cutting-plate carrier. The fitting bolts are flattened on the side and thus provide good guiding in the clamping finger 52. The same parts as described above are indicated in the drawings by the same reference symbols, so that, to avoid overburdening the description, they will not be described again.

If the clamping finger 52 has been moved after the additional griding of the cutting body 7, then a screw 60 which has an eccentric head, is to be adjusted until it again fits tightly against the clamping finger 52.

WHAT WE CLAIM IS: 1. A recess facing tool comprising a cutting-body carrier which is fixed to or integral with the side of a chuck shaft, an elongate damping finger slidably mounted on the carrier, guide means for guiding the finger in the longitudinal direction, a clamping screw clamping the finger to the carrier, and a cutting body clamped between the front end of the finger and the carrier under the action of the clamping screw, the rear end of the finder having two support faces constituting the only two points at which the finger bears on the carrier under the action of the clamping screw.
2. A tool as claimed in claim 1, in which the support faces and the cutting edge of the cutting body are substantially coplanar.
3. A tool as claimed in claim 1 or 2, in which the clamping finger is longitudinally guided without play parallel to the cutting edge of the cutting body.
4. A tool as claimed in claim 3, in which the clamping finger is guided by a key or an adjusting spring within a longitudinal groove in at least one of the adjacent faces of the clamping finger and the cutting body carrier.
5. A tool as claimed in claim 4, in which a said key is accommodated in each end of the groove.
6. A tool as claimed in claim 5, in which the keys are constituted by bolts accommodated in a longitudinal groove in the clamping finger, a flattened head of each bolt sliding in the groove.
7. A tool as claimed in any preceding claim, in which the clamping screw is remote from the cutting body.
8. A tool as claimed in any preceding claim, in which, for adjusting the clamping finger longitudinally, the rear end of the clamping finger is provided with an adjustable screw whose head bears against a pin projecting from the chuck shaft.
9. A recess facing tool substantially as described herein with reference to, and as shown in, Figures 1 to 6, or Figures 9 to 11 of the accompanying drawings.
10. A method of finishing a recess facing tool according to any preceding claim, in which the tool is finally machined in the braced condition.
11. A method as claimed in claim 10, substantially as described herein.