DE2239093A1 - LOCKING PIN FOR CLAMPING A PLATE-LIKE CUTTING TOOL INSERT - Google Patents

Description

Patent attorney D \ pl Ing. E. Günter Ottens

8 Munich HO

Josef-Raps-Str. 2

13 276

METAL CUTTING TOOLS, INC. _N

21. Airport, Rockford, 111. U.S.A.

Locking pin for clamping a plate-like Cutting tool insert.

The invention relates to a locking pin for plaguing a plate-like cutting tool insert on an insert holder. It represents an improvement of the ^{arrangement described in US Pat. No. 3 3 2} H 919, in which the locking pin is screwed into an inclined bore in the holder and is equipped with a head which is connected to one wall of a cylindrical opening wedged in the insert and presses the edge of the insert against a placement stop located on the holder while at the same time clamping it to the holder.

When comparing with known locking pins of this type it is clear that the pin according to the invention uses more securely clamped to the holder and at the same time by the forces acting on the locking pin during the final Pulling the pin after the latter has pushed the insert against the placement stop is less effective is subjected to bending. Briefly, this is achieved in that the head of the pen is formed so that a first part of the head joins one wall of the inlet opening wedged and shifted the insert to the side,

3098 1A / 0254

while a second part of the head with the diametrically opposite one Wall of the insert opening is in contact. The touch of the second part of the head with the diametrical opposite wall of the insert opening not only supports the pin against bending while it is finally tightened, but also acts to the effect that the applied Clamping force at an additional point of contact of the insert comes into effect, whereby the insert is anchored even more firmly to the holder.

The invention is illustrated below with reference to the drawing illustrated embodiments explained in more detail. In the drawing show:

Figure 1 is an exploded, partial perspective view of a cutting tool with a novel locking pin of the type described here

Figure 2 is an enlarged partial cross-sectional view along the Line 2-2 in Figure 1, which describes the installation state of the tool,

Figure 3 is a plan view of another embodiment of a Washer to hold the insert pad on the pen,

FIG. 4 shows a partial view similar to FIG. 2, but which another embodiment of a locking pin of the type described here, and

FIG. 5 is a view also similar to FIG. 2, but on an enlarged scale, showing still another Illustrates embodiment of the locking pin.

- 3 3098U / 0254

The metal cutting tool Io shown in the drawing is drawn for the sake of simplicity as a turning tool, although the essential features of the subject matter described here are also applicable to many different types of cutting tools, such as drill steels and dies. The depicted Tool has an elongated holder 11, one end of which with a pocket 13 for receiving a waffle or plate-like, adjustable cutting insert 14 made of tungsten carbide or the like is provided. The bag is held by a upward-facing platform 15 and two right-angled placement stops or walls 16, which are arranged at the inner end of the platform and from this upwards protrude.

The insert 14 preferably, but not necessarily, rests on an exchangeable base 17 on the platform 15 and its shape generally corresponds to the pocket 13, although 'it is shallower than this. the The base is hardened and serves to protect the platform against wear and damage.

In this particular case, the cutting insert 14 is approximately rectangular formed, and when it is fully seated in the pocket 13, it is clamped onto the pad 17 and platform .15 and with the edge and diagonally pressed into the corner 19, Figure 1, which is between the two placement walls 16 · lies. The latter touch the two inside edges of the insert and place the insert exactly in a cutting position, the side edges and the intervening corner above the corresponding edges of the pad and survive the platform.

To clamp the insert 14 and the pad 17 in the pocket 13, a locking pin 2o with a head 22 is inserted into an opening 21 in the insert,

- 4 3098U / 0254

inserted through a hole 23 in the base and screwed into a hole 2k extending through the holder 11. The opening 21 in the insert is approximately cylindrical and arranged centrally with respect to the insert, so that it can be rotated further in the pocket and / or turned over to bring a new cutting edge into the cutting position as soon as the active cutting edge becomes blunt. The bore 23 present in the base is arranged concentrically to the opening 21 and is somewhat larger than this opening. As is apparent from Figure 2, is the threaded bore in the holder 2 ¹ J in the vicinity of the inner end of the bore 23 and is inclined with respect to the platform 15 °. Thus, the axis a of the bore 2k , when moving upwards, tends outwardly from the corner 19 present between the placement walls 16 and is at an angle b, which is here about 15 °, with respect to the axis c that passes through the insert opening 21 inclined. The axis c runs perpendicular to the platform 15, in all planes, and both axes lie in a common vertical plane which extends perpendicular to the platform and intersects the right angle between the placement walls 16.

According to the invention, the upper end part or head 22 of the locking pin 2o is now with lower and upper sections 25 and 26 are provided, which wedge themselves with the opening 21 located in the insert 14 and cooperate in such a way that they clamp the insert in many places and thereby, together with the base 17, very firmly with the platform 15 anchor. In addition, the lower section touches a wall of the opening and presses the insert over a corner, see above that the latter moves into the corner 19 and comes to rest against the Placierungswwall 16, while the upper section 26 touches the diametrically opposite side of the opening, thereby preventing the pin from moving during

3098U / 025A ~ ⁵ "

of the final pull after the bet against the placement walls have been pressed, bends.

Accordingly, the insert is clamped more by the pin than is the case with known pins of this type wherein, moreover, the clamping position reached is maintained longer and during use of the cutting tool ^x does not lead to complaints.

In detail, the locking pin 2o has a lower threaded shaft 27 (Figure 2) which is designed so that he can be screwed into the hole 24 in the holder 11. With the upper end of the shaft is an elongated neck 29 inseparably connected, the diameter of which is slightly smaller than that of the shaft, and at the junction between the neck and the shaft is formed with a rounded throat 3o which is used for this purpose serves to reduce the stress concentration in the connection area. A similar groove 31 is on the upper one End of the neck 29 and forms the connection between the Neck and the lower portion 25, which preferably has the shape of a truncated cone. Figure 2 shows that the lower truncated cone 25 tapers at a cone angle d, which here is equal to the angle b between the axes a and c of the bore 24 and the opening 21 so that the inside of the truncated cone 25 runs parallel to the inner wall 35 of the opening 21, when the locking pin 2o is screwed into the bore 24.

The larger diameter of the upper end of the lower truncated cone B. 25 is slightly smaller than the diameter of the opening 21 and is equal to the diameter of a cylindrical section tes 36 (Figure 2), the. on the upper end part of the pin between the lower truncated cone 25 and the upper section 26 is formed, which also has the shape of a truncated cone. the upper truncated cone 26 has a large one Diameter equal to the diameter of the cylindrical

3098U / 025A

Section % is and tapers starting from the cylindrical section upwards to at a cone angle e, which is also equal to the angle b between the axes a and c. As a result, the outside of the upper truncated cone 26 runs parallel to the outside wall 37 of the opening 21 when the pin 20 is screwed into the bore 24. In order to enable the pin to be screwed in, an upwardly opening socket 39 is formed in the upper end part of the pin and is shaped so that it can receive a suitable torque transmission tool, for example a wrench. A similar socket, not shown, opens towards the lower end of the shaft 27 to enable the pin to be rotated from the lower side of the holder 11 if this is required or the upper socket 39 should be damaged after prolonged use,

To install and lock the insert 14, the Support 17 is arranged on the platform 15, whereupon the pin 2o is screwed into the bore 24 in the holder 11 will. Initially, when installation of the pen has just begun, the cylindrical section is located 36 well above the pad and outside of the placement walls 16. In this position of the pin, the radial distance between the placement walls 16 and the neighboring ones is Sides of the cylindrical portion 36 smaller than the radial distance between the inner edges of the insert 14 and the adjacent walls of the opening 21, as a result of which the insert can be slid over the upper end part of the pin slide away and arrange on the surface.

The pin 2o is then screwed into the bore 24, around the upper end part of the pin downwards into the opening 21 to pull in. As a result, the inside of the lower truncated cone 25 touches the inside wall 35 of the opening 21, whereby it presses against it like a wedge and the insert 14 with it

309814/0264 " ⁷ "

-K-

the edge and diagonally towards the corner 19 between the two placement walls 16 while pushing it down. In other words, the radial distance between the lower truncated cone 25 and the placement walls 16 decreases when the pin 2o is tightened, and due to the inclination of the bore 24 and the inclination of the truncated cone, there is a horizontal and vertical component on the insert exhibiting force exerted.

The horizontal component of this force pushes the insert with the edge sideways towards corner 19 and against the placement walls 16, while the vertical component acts on the triangular portion of the insert that is inside the opening 21, and serves to clamp this section down on the base 17 and the base also clamp down on the sheet form 15.

When the inner edges of the insert Ik are pressed against the placement walls 16 and are stopped by them, and when the pin 20 is tightened further, the upper end portion of the pin tends to move against the inner wall 35 of the opening 2L due to the lower truncated cone 25 »of of the stopped insert is pressed to bend outward. Such a bending movement, however, is opposed to resistance during the final pulling of the pin, which resistance limits it because the outside of the upper truncated cone 26 contacts the outside wall 37 of the opening 21. Due to such contact, the upper end portion of the pin is supported and carried by the upper truncated cone 26 and the outer wall 37, thereby limiting the outward deflection of the pin. In addition, the outer side of the upper truncated cone 26 is pressed against the outer wall 37 and exerts a downward force on the triangular part of the insert which lies outside the opening 27. This part of the stake will _{t go} down this way

- ^; ■■ --- ■ "■■ - 8 - 30 & 8U / 02S4

the base 17 is clamped, while the base itself is also clamped downwards to the platform 15.

fit Xs

As a result, both the inner / outer become triangular Section of the insert clamped by the locking pin. In the final clamped position of the The middle part of the cylindrical section is located on the pin 36 approximately at the intersection f of axes a and c.

From the above it follows that a new and improved locking pin 2o is created here, which on the insert 14 due to the lower and upper truncated cones 25 and 26, which are attached to the inner and outer walls 35 or 37 of the opening 21, is able to apply a downward-facing onto the insert 14 at two points of contact To exert clamping force. In this way, a secure clamping of the insert is achieved. It also works. the lower truncated cone to the effect that it pushes the insert to the side against the stop walls 16, while the upper Truncated cone of the bending load on the pin under the forces acting on the pin when the use of the Stop walls is brought to a standstill, opposes resistance. The one between the truncated cones and the walls the line contact occurring due to the opening 21 the correlation of the cone angles d and e of the truncated cone with the angle of inclination b between axes a and c and due to the central cylindrical portion 36 which allows the insert to initially be slid onto the pin and nevertheless a dimensioning of the truncated cones with a sufficiently large diameter to avoid the line contact to obtain.

To the basic advantages of the construction described here to achieve it is necessary that'daο upper and lower toi] ο dos head 22 as Ke ^ eI blunt aii3 (eM l <i (t. aiiul, so] aii | ', (! as the head iso boniasnen and {, (! forms iijt, daft

^BA0 ORIQ, _NAL

one part of the head touches one wall of the opening 21, while the other part is in contact with the diametrically opposite wall in essentially the same way as the truncated cones. For example, FIG. 4 shows a locking pin 2o ^f with a head 22 ', the lower and upper parts 25' and 26 'of which have a radius of curvature or are rounded. Surfaces .n surfaces and are not provided with beveled surfaces. The inner surface of the lower part .25 'contacts the inner wall of the opening 21 at a point A, while the outer surface of the upper part 26' contacts the outer wall of the opening at a point B, thereby achieving essentially the same effect as it was reached by the truncated cones 25 and 26, but the advantage of the line contact between the head and the walls of the opening does not exist.

The locking pins 2o 'shown in Figure 4 not only indicate that the upper and lower parts of the head do not necessarily have to be in the form of truncated cones, but also show that the uppermost point of contact A of the lowermost part 25 ^f and the lowest point of contact B of the upper part 2β need not necessarily lie in a horizontal plane which contains the point of intersection f between the axes a and c.

Even if this is not the best option from the standpoint of excellent design technology, the locking pin 2ο ¹ 'shown in FIG. 5 indicates that the head 22' * can have quite extreme shapes and still have the fundamental advantages of those described here Can achieve construction. In this case, the lower part 25 * 'has a considerably larger diameter than the upper part 26 ", and as in the case of pin 2er ¹ , neither the uppermost point of contact A of the lower part 25" lies.

- Io 309014/0254

still the lowest point of contact B of the upper part 26 '' in the horizontal plane containing the intersection f of axes a and c. Also is the contact surface of the lower Part 25 '' rounded while the contact surface of the top Part 26 "is designed as a truncated cone.

A consideration of the locking pin 2o ″ of FIG facilitates the explanation of the basic relationships by which the head can be sized and shaped to conform to the basic idea of the invention. First of all, the point of contact A should be in or below a horizontal plane lie that. contains the point of intersection f, while the point of contact B lies in or above such a plane target. Furthermore, it is clear that the largest radius of the head can never be larger than the smallest radius r the opening 21 which leads through the insert 14. Due to the fact that the axis a of the bore 24. with respect to the axis c of the opening21 is inclined, the largest radius of the head must also always be smaller than the radius r of the opening, so that the pin can be inserted into the opening and screwed into the bore. The largest dimension any given radius of the head depends on the inclination angle b of the axis a with respect to the axis c, as well as the distance along the axis a of this respective radius from the point of intersection f. In no case can any Radius of any part of the head inside the opening have a larger dimension than r cos b, otherwise the pin cannot be inserted into the opening 21 and cannot be screwed into the bore 24. In the end the points of contact A and B along the axis a must be separated from the point f by distances that are not less than f are called r sin b so that the head insert 14 correctly clamps and limits the bending of the pin. If the radius of the head at any of the points of contact is equal to the Value r coa b, then such a radius should be along the

3098U / 02S4 ~ ^U "

2239033

Axis' a from the point f have a distance equal to the value r sin exceeds b by 0.0254 mm or so for the pin the insert 14 can clamp properly. When the radius of the head is made smaller at a given point of contact is equal to the value r cos b, then the distance of the radius from the point f must be increased, and although according to a puncture described below.

It is now assumed that the radius of the lower portion 25 "of the head 22" at the point of contact A should have a given dimension R ₁ that is equal to or less than r cos b, and that the radius of the upper portion 26 ^ft at the point of contact b a given dimension R "should have, which is also equal to or smaller than r cos b. If these dimensions are known, then the distances D ₁ and D ₂ by which the radii R ₁ and Rp should be removed from the point of intersection f along the axis a can essentially be determined according to the following equations:

l ₎

D ₁ = r sinb 4 ¹

tangb

= r sin b + Z

tangb (2)

To explain the derivation of equation (1), reference is made to the two right-angled triangles E ₁ , G ₁ , f and E ₁ P ₁ A from FIG. Now the distance D ₁ can be expressed as follows:

D ₁ = G _a f + E ₁ A. (3),

And this Ab is, and G ₃ f leaves "ich- r.chreibon :. . . ...., - ,,, -,

E ₁ ^ f sin b r _S inb

The distance F. A can be expressed as follows: '

And the distance

Vl tangb F ₁ is the same

(7)

The distance

is then:

^E 1 ^G 1 ^{= E} l ^{f C0S b}

= r cos b

(9)

By substituting r cos b for, E ₁ F ₁ becomes:

in expression (7)

r cos b -

(l.o.)

And by substituting r cos b (6) the value of F ₁ A becomes:

for EJB * in the expression

r cos b -

tangb

(11)

Finally, the values for G ₃ / and F ₁ A contained in expressions (5) and (11) can be substituted for the corresponding values in equation (3),

3098U / Q2S4

- 13 -

-j «- j ₃ 2239033

so that the equation (# results in:

D ₁ - sin b + g cog b - H ₁

tang b *

Equation (2) can be derived with respect to the distance D by using the same method with respect to the triangles EgGg * ¹ and EgF ₂ B of FIG.

In summary, it can be stated that effective contact between the lower part 25 "of the head 22 '' and the inner wall of the opening 21 and between the upper one Part 26 ″ of the head and the outer wall of the opening can be effected independently of the head shape in that the head is measured * so that:

(A) The uppermost point of contact A between the lower end part 25! ^{M of} the head and the inner wall of the opening does not lie above the point of intersection f and is separated in the radial direction from the axis a along a radius of dimension R ^ which is not greater than r cos bj

(B) The lower point of contact B ^ between the upper end part 26 "of the head 22 * * and the outer wall of the opening 21 is not below the point of intersection f and is separated in the radial direction from the axis a length of a radius of the dimension Rg, which is not greater is ala ρ oot b |

(C) The point of contact A and the point of contact B along the axis a, separated from the point of intersection f by the distances D ₁ and D _2, which are not smaller than F with H

(D) Pie distances D ₁ and D ₂ from the dimensions R ₁ and R

essentially depend on one another in accordance with equations (1) and (2).

Of course, good design techniques dictate other factors, such as the shape of the head, the location of the contact points A and B, and the size of the head at locations other than the contact points. In addition, as mentioned above, all given radii H ₁ and R ₂ chosen for the points of contact A and B should be at a distance from the intersection f that is a few thousandths of a millimeter greater than the values for D ₁ and D ₂ obtained by equations (1) and (2) so that an interference fit is created between the head 22 "and the opening 21 which ensures proper clamping of the insert 14. Once the contact points have been established, the radius of that The part of the head that is below the point of contact A will get smaller the further the head pushes down, and for the same reason the radius of that part of the head that is above the point of contact B should decrease the further the head is If the upper and lower parts of the head are to be formed as truncated cones in order to make a line contact with the walls of the opening 21, then the radi en of the upper and lower parts decrease substantially in accordance with equations (1) and (2) when the lower part moves downward from the contact point A and the upper part moves upward from the contact point B. In addition, the distance is along the axis a between any given point of contact on the upper part of the head and any given point of contact on the lower part of the head equal to the sum of equations (1) and (2) and «was regardless of whether the upper and lower parts are rounded or are designed as a truncated cone.

309814/025 *. . oh «nju.

As can be seen from Figures 1 and 2, are on means are advantageously provided with which the pad 17 is captured on the locking pin 2o, so that the pad is retained on the pin when the latter is released for replacement or further rotation of the insert 14 to enable. This is where these means exist from a circular disc 45 (Figures 1 and 2), which from Neoprene or another resilient material is manufactured and is provided with an eccentric opening 46. If the disc is relaxed, then this is it The diameter of the opening 45 is somewhat larger than the diameter of the neck 29, but smaller than the diameter of the shaft 27 and the smaller diameter of the lower truncated cone 25. The opening 45 can be enlarged by stretching the disk, so that the disc can be snapped over the upper end portion of the pin 20 to slide down into the neck 29 encompassing layer to be pushed. If the disc can relax, it will be placed on the neck between the Shank 27 and the lower truncated cone 25 held.

As can be seen from Figure 2, the disk 45 sits in a counterbore 47 in the upper end of the base 17 and lies under the underside of the lower truncated cone 25 when the pin 2o is screwed into the bore 24. If so, the pen is resolved so the use. 14 exchanged or rotated further can then be held, the touch of the disc 45 · with the lower truncated cone the pad 17 from it after to be removed from the top of the pen.

Another disk 45 ^f is shown in Figure 3, and in this case the disk is made of metal and is provided with a slot 5o which opens outwards at one edge of the disk and the width of which is slightly greater than the diameter of the neck 29, but smaller than the diameter of the shaft 27 and the smaller diameter of the lower one

- 16 3098U / 02S4

Kegelatumpfes 25. The disk 45 'can be over from the edge slide the neck 29 before the pin 2o is tightened, and when the washer is then seated in the counterbore 47, lie the edges of the slot 5o under the underside of the lower truncated cone 25, so that a removal of the pad 17 from the top of the pen. A removal the pad to the side is avoided in that the inner wall of the bore 23 with the upper end portion of the shaft 27 comes into contact.

For a better understanding, the cutting tool Io is in the The drawing is provided with the insert 14 facing upwards and each locking pin is described with "upper" and "lower" parts provided. Although the terms "above" and "below" and similar terms are directional or orientation information these terms are used here for convenience only. It is understood that what is presented here Cutting tool Io and that other cutting tools, in which the inventive proposal can be used, do not necessarily have to be oriented so that the insert is facing up, but in reality many different ones Can take up positions. The above terms used here, the direction and orientation in vertical Indicate senses are therefore only to be understood as reference values, which are used as soon as any particular tool is oriented so that the opening in its insert pointing roughly upwards.

- 17 30981 A / 025 /.

Claims (15)

Patent attorney Dipl. Ing. E. Günter Otfens 8 Munich 4-O Josef-Raps-Str. 2 2239093 f7 Claims !. ^ Locking pin for the fixed arrangement of a plate-like cutting _{insert on an insert holder, which has an upward N} platform for receiving the underside of the insert, and an inner stop, which is directed from the platform upwards to one edge of the To come into contact with the insert and thereby place the latter in a cutting position, with an approximately cylindrical opening which extends through the insert and has an axis c which is essentially perpendicular to the platform, and with a bore located in the holder, which opens to the top of the platform, characterized "in that the bore (24) has an axis (a) which extends outwardly from the stop (19) the further it goes upwards and the below a certain Angle (b) is inclined to the axis (c) of the opening (21) so that the locking pin (2o) has a lower shaft (27) which extends into the Bohru ng (24) extends into and is tightenable in it, and an upper head of approximately circular cross-section, which is so dimensioned and shaped that the lower end portion (25) of the head contacts the inner wall (35) of the opening (21) around the Insert (14) laterally against the stop (19) to push, and that the upper end part (26) of the head touches the outer wall (37) of the opening (21) in order to limit the bending of the pin (2o) and the plague clamping of the Use on the platform. 2. Locking pin according to claim 1, characterized in that the size and Rrm of the head are dimensioned so that the uppermost point of contact between the lower end part (25) of the head and the inner wall (35) of the opening (21) does not extend above the intersection ( f) the axes (a and c) are located and separated from the axis (a) along a radius of dimension (R ₁ ), furthermore the lowermost point of contact between the upper one - 18 309814/02 The end part (26) of the head and the outer wall (37) of the opening (21) is not below the intersection (f) and _{is away from the axis (a) along a radius of dimension (R 2} ), furthermore the lowermost point of contact and the uppermost point of contact along the axis (a) from the point of intersection (f) have the distances (D ₁ and D ₂ ) which are not smaller than r sin b, where r is the smallest radius of the opening (21) Dimensions (R ₁ and R ₂ ) are not larger than r cos b, and that finally the distances (D ₁ and D ₂ ) with the dimensions (R ₁ and R ₂ ) are essentially functionally related as follows: D ₁ = r sin. b + ^{r co3 b} " ^R l tang b D ₂ = r sin b + ^{r cos b TR} 2 tang b 3. The locking pin of claim 1, wherein the head is sized and shaped such that a radius of dimension (R ₁ ) of the lower end portion (25) of the head contacts the inner wall (35) of the opening (21) at a first point of contact while a radius of dimension (R ₂ ) of the upper end part (26) of the head touches the outer wall (37) of the opening (21) at a second contact point which is separated from the first contact point along the axis (a) at a distance, and that the distance between the points of contact along axis (a) is substantially the same 2r sin b ♦ ^{r coa b} - ^R l ♦ ^{r cos b} " ^R 2 tang b tang b where r is the smallest radius of the opening (21). 4. Locking pin according to claim 2 or 3, characterized in that that the head is provided with rounded surfaces at the contact points (A), (B) '. 309814/0254 - 19 - 5. Locking pin according to one of claims 1-3, characterized characterized in that the head is provided with oppositely tapered truncated cones (25, 26). 6. Locking pin according to one of claims 1-3 _S, characterized in that the shaft (27) is screwed into the bore (24), that the lower end part (25) of the head has a lower frustoconical section which tapers downwards and comes into wedge-like contact with the inner wall (35) of the opening (21) in order to press the insert (14) laterally against the stop (19) while it is clamped on the platform (15), and that the upper end part ( 26) of the head has an upper, frustoconical section which tapers towards the top and comes in wedge-like contact with the outer wall (37) of the opening (21) in order to prevent the pin (2o) from bending at the connection point of the upper end part (26 ) to reduce the undoes shaft and to support the clamping of the insert (14) on the platform (15). 7. Locking pin according to claim 6, characterized in that the head of the pin (2o) has a cylindrical section (36) has, between the upper and the lower frustoconical Section (26, 25) lies. 8. Locking pin according to claim 7, characterized in that the diameter of the cylindrical portion (36) is the same the larger diameters of the frustoconical sections (25, 26) and is slightly smaller than the diameter of the Opening (21). 9. Locking pin according to claim 7 or 8, characterized in that that the axis (c) of the opening (21) is the axis (a) of the bore (24) approximately in the middle of the cylindrical sections (36) cuts. ■, _J0 .-- , -2ο-309 8 U / 0254 10. Locking pin according to one of claims 6-9, characterized in that the cone angle (d) of the lower truncated cone section (25) is approximately equal to the cone angle (e) of the upper portion (26) and approximately equal to the predetermined angle (b), so that the inside of the lower frustoconical section substantially runs parallel to the inner wall (35) of the opening (21), while the outer side of the upper frustoconical section in the runs essentially parallel to the outer wall (3D of the opening. 11. Locking pin according to one of claims 6 - lo, characterized in that the pin (2o) has an approximately cylindrical Has neck (29), the diameter of which is smaller than that of the shaft (27) and smaller than the smaller diameter of the lower frustoconical portion (25), and that the neck (29) between the shaft (27) and the lower frustoconical section (25). 12. Locking pin according to claim 11, characterized by a base (17) which ^{is / is arranged between the insert (I 1} I) and the platform (15) and is provided with a bore (46) for receiving the pin (2o), one wall of which can be brought into contact with the pin in order to prevent the pad (17) from moving laterally away from the pin (2o) Disc (45, 45 ') is inserted, which is provided with an opening (46), the edges of which surround the neck (29) and can be brought into engagement with the lower end of the lower frustoconical part (25) in order to remove the pad (17) from the head of the pin (2o) upwards as soon as the latter is loosened and the insert (14) is removed from the holder (lo). 13. Locking pin according to claim 12, characterized in that the disc (45, 45 ') consists of a resiliently yielding -? A 3098U / 0254 2239033 Material consists, and that the opening (46, 5o) in the Disc in the relaxed state has a diameter that is smaller than the larger diameter, the lower frustoconical part (25) and is so expandable that it enables the disc to be slipped onto the pin (2o), 14. Locking pin according to claim 13 »characterized in that that the opening (46) in the disc is arranged eccentrically in adaptation to the pin (2o) ·. 15, locking pin as claimed in claim 12 _s characterized in that the opening (5o) (45 ') is a slit in the disc belonging to the open one edge of the wafer back and has a width that is greater than the diameter of the neck (29) and smaller than the larger diameter of the lower frustoconical part (25) 3098U / 025A