CH684174A5 - Method of reaming and reaming head which is adjustable for small diameters - Google Patents

Abstract

The method of reaming for small diameters uses an adjustable reaming head (1) which particularly comprises a body (11), separated into two parts (11A, 11B) by a slot (12). By acting on a screw (15) arranged in a tapping (14) made within one (11B) of the parts of the body, it is possible to separate the two faces of the slot and consequently to shift the axis of one of the parts of the body with respect to the other. If a cutter or reaming tool (2) is fixed to one of the parts (11B) while the other part (11A) is secured to the spindle (30) of the tool holder headstock (3), the end of the tool (25), or the reaming tip fixed to the extremity of the tool, can take up any radial position according to the off-axis angle ( alpha ) set between the two parts of the body. Different embodiments of the reaming head, and particularly of the method of fixing the reaming tool onto the said reaming head, are proposed. <IMAGE>

Description

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Description

The present invention relates to a reaming method and an adjustable reaming head, which can be used particularly for reaming small diameter holes.

Precision boring of a hole is generally carried out using a chisel or a boring tool, rotating in a spindle, and which comprises at its end a boring plate boring said hole according to a predetermined diameter.

For a hole whose diameter is relatively large, this operation is fairly easy since the dimension of the reaming tool is sufficient for the reaming insert to be adjustable in the radial position, thus allowing continuous adjustment of the diameter to be reamed. .

It is not the same for a small diameter hole, the reduced dimensions of the reaming tool generally do not allow the installation of an adjustable device, which would further reduce the rigidity of the tool too and therefore its machining precision.

On the other hand, the boring tools are provided in a non-continuous dimensional range, which makes it difficult for holes of small diameters to find exactly the right tool; the same applies when the tool has already been used and has been resharpened, which means that its dimensions are no longer standardized.

In order to avoid these drawbacks, a first adjustable tool holder had been produced, comprising a tail which is fixed in the spindle of the headstock of the boring machine, said tool holder comprising a central body in two parts, sliding between them in a direction perpendicular to the axis of rotation of the tool, the tail of the tool holder being integral with the first of said parts while the tool to be bored is fixed to the second of said parts. Thus, by acting on the slide separating the two parts of the central body, it is possible to offset the point of attack of the bore plate by any value. If this boring head perfectly fulfills the purpose for which it was designed, it nevertheless has some drawbacks which limit its use; in particular, the second part of the central body, off-center relative to the axis of rotation of the tool, creates an unbalance capable of generating vibrations harmful to the required precision, on the other hand given the relative complexity of this head , it is quite expensive.

An object of the invention is to propose a reaming method making it possible to ream holes of small diameters with a limited range of tools, this for any value of diameter comprised between the two extreme values of the range considered , while another object of the invention is to propose a simpler and cheaper boring head which makes it possible to use said method and which can work at high speed of rotation.

To respond to this, a boring method according to the invention is proposed, comprising the characteristics mentioned in claims 1 to 2, and an adjustable boring head according to the invention is proposed, comprising the characteristics of claims 3 to 10.

To better understand the object of the invention, reference can be made to the accompanying drawing with the figures in which:

fig. 1A represents a boring head according to a first embodiment,

fig. 1B represents the same boring head seen at the end,

fig. 2A represents a boring head according to a second embodiment,

fig. 2B represents the same boring head seen in section,

fig. 3 shows a boring head according to a third embodiment, and FIG. 4 shows a boring head according to the embodiment of FIG. 3 in use.

In common with the various embodiments shown in the figures, the boring head 1 is composed of a shank 10 as well as a body 11, these two elements being generally of cylindrical shape and being arranged in the extension l one of the other. The shank 10 is intended to hold the boring head 1 in a tool holder spindle and therefore has the dimensions and the shape necessary for this use; for example it can also not be cylindrical but cone-shaped. The body 11 comprises a slot 12, arranged transversely to the longitudinal axis of the head to be bored, over a portion of the section of said body, said split portion being larger than half of said section. In order to avoid excessive mechanical stress on the body section 11C remaining in the plane of the slot 12, said slot ends in a portion of cylindrical hole 13, drilled in the same plane as that where the slot 12 is located and the axis of which coincides with the fictitious edge ending said slot. The slot 12 determines 2 portions of the body 11, a first portion 11 A, located near the tail 10 is on which said tail is fixed, and a second portion 11B, located on the other side of the slot 12, both portions 11A and 11B being connected by section 11C. Preferably, the height of the second portion 11B is greater than that of the first portion 11 A. A tapped hole 14 is arranged in the second portion 11B of the body

11, the axis of said tapped hole being parallel to the longitudinal axis of the head to be bored, but offset with respect to said longitudinal axis in the direction exactly opposite to that where the transverse hole portion is located 13. A screw 15 is engaged in the tap hole 14, passing entirely through the second portion 11B of the body 11, as well as the slot

12, so that the lower end of said screw comes to bear against the face of the first portion 11A of the body 11 created by the slot 12.

Thus, by continuing to screw the screw 15 inside the tapped hole 14, after the latter has pressed against the face of the first portion 11 A, there is a tendency to separate the two faces of the slot 12. Since the first portion 11A of the body 11 is closed5

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ment held by the shank 10 in the spindle of the tool holder headstock, it is the second portion 11B of the body 11 which will tend to be offset with respect to the first portion 11 A, respectively with respect to the axis of the tool holder headstock spindle, section 11C acting as a hinge between the two portions 11A and 11B.

According to a second and third embodiment of the body 11, visible in FIGS. 2A, 2B and 3, another portion of transverse hole 16 is arranged in section 11C, in the same transverse plane as that containing the slot 12, parallel to the first portion of transverse hole 13, on the portion of opposite section 11C to that where said first transverse hole portion 13 is located, a portion of the surface of said hole intersecting the cylindrical outer surface of the body 11. In this way, the section of material remaining in section 11C is reduced, which makes it possible to increase the offset angle that it is possible to obtain between the two portions 11 a and 11 B.

Apart from that mentioned above, the difference between the three embodiments of the boring head shown in FIGS. 1A, 2A and 3 resides in the method of fixing the reaming tool 2. The reaming tool is fixed on the free front face of the second portion 11B of the body 11, ie on the side opposite to that where is the tail 10.

According to a first embodiment of the method of fixing the tool or the boring chisel, visible in FIG. 1A, a bore 20 is arranged in the second portion 11B of the body 11, coaxial with said portion, and whose diameter corresponds to the diameter of the tail of the tool which will be mounted there. The bore 20 can be extended in the first portion 11A by a blind bore portion 20A, intended to receive the end of the tool shank, said bore portion 20A having a diameter greater than that of the bore 20 so that the end of the shank of the tool can find room there when the second portion 11b, respectively the bore 20 is offset from the first portion 11A, respectively to the portion of 20A bore. Another tapped hole 21, perpendicular to the bore 20 is drilled in the second portion 11B, opening on one side into said bore and on the other side on the cylindrical outer face of the portion 11B. The tail of the reaming tool can therefore be fixed in the bore 20 by means of a screw engaged in the tapped hole 21. In order to identify during assembly the direction in which the offset occurs, a reference 22 can be affixed to the front face of the second portion 11 B, which is used to position the boring tool, respectively the boring plate of said tool.

Another embodiment of the fixing method of the boring tool is visible in FIG. 2B, where a clamp 23, of known technique, is mounted in extension of the body 11. A bore 24 is provided in the portion 11 B, behind the clamp, in order to receive the rear end of the shank of the tool . An advantage of this embodiment of the tool attachment method is that it is possible to install boring tools of different shank diameters on the same boring head; this embodiment is particularly used for tools of very small diameter. As previously, a reference 22 can be provided on the front face of the clamp 23 or of the body portion 11B in order to facilitate the mounting of the tool to be bored.

According to the third embodiment of the fixing method of the boring tool, visible in FIG. 3, the boring tool 2 is directly welded or screwed in the extension of the body 11 in order to form a one-piece tool.

Fig. 4 shows the use of the boring head according to the invention, according to the same embodiment of the tool attachment mode as that of FIG. 3. The tail 10 of the boring head 1 is fixed inside the spindle 30 of the tool holder headstock 3, in rotation along the longitudinal axis of the machine. A part 31 is fixed to a part holder, not shown. A bore is to be produced inside said part, by the bore tool 2 fixed on the bore head 1. In order to bring the bore plate 25 into the working position, the second portion 11B of body 11 has been offset by a value a relative to the first portion 11A by acting on the screw 15 to separate the two faces of the slot 12. By tightening the screw 15, the offset angle a, is adjusted in bringing the plate 25 into contact with a reference surface 32, integral with the machine, and located at the correct bore dimension, or else in contact with a presetting device such as a telescope or a comparator.

The method and the boring head according to the invention have been described relating to a reaming operation where the reaming tool is rotated inside a boring part which is fixed, but they can all as well be used on a machine where it is the part which is rotating around a fixed tool.

The offset angle shown in the figure has been greatly exaggerated to allow a better understanding of the process; in reality the offset angle that can actually be obtained is of the order of 2 ° to 3 °; this value is clearly sufficient to achieve the aims of the invention, that is to allow boring a hole of small diameter, of any nominal value, using a limited number of boring tools and a head. relatively easy to perform reaming, the reaming operation being able to be carried out at high speed of rotation of the tool, given the small offset of the second portion of the boring head.

Claims (1)

Claims 1. Boring method of small diameters, characterized in that the longitudinal axis of a tool or a chisel to be bored (2) is displaced, by means of a boring head supporting the tool or the chisel , so that this axis is offset at a certain angle (a) relative to the axis of rotation of a spindle of a boring machine now the boring head. 2. Method according to claim 1, characterized in that the offset of the longitudinal axis of the tool or of the chisel to be bored with respect to the axis of rotation of the spindle is obtained by spacing the two faces of a slot (12) arranged transversely in a body (11) of the boring head (1). 5 10 15 20 25 30 35 40 45 50 55 60 65 3 5 CH 684 174 A5 3. Boring head for implementing the method according to one of the preceding claims, comprising a tail (10) intended to be fixed in the spindle (30) of the boring machine (3), and the body (11 ), a first portion (11 A) of which is fixed to said shank, and a second portion (11 B) of which is intended to receive the tool or the chisel to be bored (2), characterized in that said body comprises the slot (12), arranged in a transverse plane, on a part offset from the cross section of said body and separating the two said portions (11 A, 11B). 4. Boring head according to claim 3, characterized in that said body comprises a first transverse bore (13) whose axis corresponds to the fictitious edge ending the slot. 5. Boring head according to claim 4, characterized in that said body further comprises a second transverse bore (16) disposed in the same plane as said slot and whose axis is parallel to the axis of said first transverse bore and the cylindrical surface of which is cut by the external cylindrical surface of said body. 6. Boring head according to one of claims 3 to 5, characterized in that said second body portion has a tapped longitudinal bore (14) opening on a first face of said slot, a screw (15) being disposed in said tarau-dage, the end of which abuts against part of the second face of said slot. 7. Boring head according to claim 6, characterized in that the second body portion (11B) has a bore (20) perpendicular to the front face of said second body portion and intended to receive the tail of the tool or chisel to be bored. 8. Boring head according to claim 6, characterized in that the second body portion comprises a clamp (23) disposed perpendicular to the front face of said second body portion and intended to receive the tail of the tool or chisel to ream. 9. Boring head according to claim 6, characterized in that the front face of said second body portion is arranged so that the tail of the tool or chisel can be welded or screwed perpendicular to said front face. 10. Boring head according to one of claims 7 or 8, characterized in that the front face of said second body portion comprises a mark intended to align the tool or the chisel to be bored. 5 10 15 20 25 30 35 40 45 50 55 60 65 4