US2152567A - Chaser for die heads - Google Patents

Description

Ema/Mom March 28, 1939. c. A. REIMSCHISSEL CHASER FOR DIE HEADS Filed July 3, 1937 Patented Mar. 28, 1939 2,152,567 cmsaa Fox ms nmns Charles A. Reimschissel, Waynesboro', Pa" assignor to Landis Machine Company, Waynesboro, Pa., a. corporation of Pennsylvania Application July 3, 1937,Serial No. 151,913

5 Claims.

This invention relates to thread cutting chasers and holders and particularly to chasers of the tangential type.

Chasers of this kind are, as is well known in the art, held in suitable holder blocks by means of clamps drawn into firm engagement with clamping surfaces provided on the chasers. An example of this kind of chaser mounting is had in United States Patent No. 1,906,176, granted to S. F. Newman et al. on April 25, 1933. As will be readily understood, a considerable force must be exerted on the chaser by the clamps to the end that the chaser is held firmly against the co-operating seating surface on the chaser holder to prevent relative movement between these two elements. Also, in order to insure accuracy and uniformity of performance of the respect to the seating surfaces, which not only, results in inaccuracies in the cutting action, but,

furthermore, tends to greatly reduce the force of friction between chaser and holder thereby making it possible for the chaser to move slightly with respect to the holder under the reaction forces set up during the cutting operation.

It is, therefore, a major object of this invention to provide an improved thread chaser and holding means so designed that the resultant of the force exerted by the holding or clamping means is directed centrally of the seating surfaces and perpendicular thereto, whereby the tendency of the clamping force to tilt the chaser is obviated. 7

Another important object of my invention is to provide a chaser or thread cutting tool with clamping and base seating surfaces so arranged with respect to each other and to a back seat ing surface that the clamping force is reflected by the first two surfaces as a resultant acting centrally of and perpendicular to the back seating surface of the chaser and also centrally of and normal to the seating surface of the holder.

A still further object of my invention is to provide a novel and improved chaser holder and clamp in which the clamp seating surface of the holder and the clamping surface of the clamp are each inclined equally from a line parallel to the clamp securing means whereby the force applied to the chaser is directed parallel to the back seating surface of the chaser and thus intersects the clamping surface of the chaser and In devices of this character, the force applied by the clamping means is of considerable magnitude, as has been previously noted, and, furthermore, the chasers are made of high speed steel which sometimes leads to failure of the chaser by cracks starting at the acute angle of the dovetail usually provided adjacent to the chaser clamping surface. It is, therefore, a still further object of my invention to provide an improved thread chaser which is formed so as to eliminate this sharp angle between the clamping surface and the body of the chaser thereby preventing the formation of incipient cracks and greatly enhancing the strength and life of the chaser.

Also, in chasers of this type, wherein the clamp seats against an inclined clamping surface, another place of weakness is present at the juncture of the clamping surface and the back seating surface of the chaser. Due to the relative brittleness of the material used for the chasers and the intensity of the clamping force, the thin and sharp edges formed by the aforementioned surfaces is very often chipped or broken under the clamping action. Thus, a still further object of my invention is to provide an improved chaser in which a comparatively thick edge is located at the juncture of the clamping surface and back seating surface, which thickened edge is sufficiently strong to withstand the clamping forces.

The above, and further objects, will become apparent from a study of the following detailed description of a preferred embodiment of my invention together with the appended claims when considered in conjunction with the accompanying drawing, in which:

Figure 1 is a face view of a die head provided with a set of chasers in their holders and embodying my invention.

Figure 2 is a partial section through a chaser and its holder taken on the line 2-2 of Figure 1, and on an enlarged scale.

Figure 3 is a view similar to that of Figure 2, taken on the line 3-3 of Figure 1.

Figure 4 is a face view of the improved chaser of my invention; and

Figure is an end view of a slightly modified form of chaser.

Referring now to the drawing, in which like reference characters are used to designate the same elements wherever they appear in the several views, and with particularreference to Figure 1, the reference character 2 designates a conventional die head carrying holders 4. Chasers 6 are mounted in the holders by means of clamps 8 held in place by screws ll.

' Turning now to Figure 2 and 8 wherein the shape of my improved chasers, holders, and clamps are shown, chaser 8 is provided with base seating surface i2, back seating surface It, and clamping surface l4. Small beveled surfaces It and 20 connect these three surfaces as will be evident upon inspection of these views. The surface I4 formsa dovetail and is connected by undercut surface 22 to a seating surface 24, the latter being parallel to, but offset from, surface it. Surfaces I-4 and 22 are formed by a curved surface or fillet 20, the purpose of which will be explained later. Chaser t is provided with cutting serrations 20 and a leading edge 30 in the usual manner.

Surface It bears against aco-operating flat surface 32 on holder 4, and base surface i2 bears against a co-operating surface 34. Surface 24 rests against a surface ll to give support to the leading edge of the chaser. The holder is also provided with a surface ll on which rests an end surface 40 of clamp l. The opposite end of the clamp carries an inclined surface 42 engaging surface i4 of chaser 8.

The angular relationship of the several surfaces is illustrated by the broken lines R, :c, y, and 'z and angles H in Figure 3. Surfaces 30 and 34, and co-operating surfaces 40 and I2 are parallel (see lines 1 and u) Surfaces l2 and I4 are each inclined equally with respect to surface it (see lines 1! and z and angles ma). Since the axis of screw it is parallel to surface :2, it follows, by simple geometry, that surfaces I4, 42 and 38, 40 are equally inclined with respect to the line of action of the force exerted in holder 8 by the screw IO.

Upon tightening of screw II, the clamp is pressed at one end against surface a while the other end bears on the inclined surface l4 of the chaser; and, as will readily be understood, the chaser is firmly held in place'in the holder by screw it with surfaces It and 32 and surfaces 24 and 36 pressed together, and with surfaces i2 and 34 also engaged.

It will be observed that, due to the equal in,- clinatlon of surfaces ll, 40 and I4, 42 with respect to the direction of the force exerted by the screw it, the resultant force acting on chaser surface l4 will be directed in parallelism with the surfaces It and 82. Furthermore, as surfaces l2 and H are equally inclined with respect to the surface It, the resulting clamping force reacts equally against each side of the chaser 6, on the surfaces I4 and I2, and the back seating surface it is forced against the surface 32 of holder ill with a uniform pressure throughout. In other words, the resultant of the clamping force acts normal to and centrally of surfaces It and 32 (see line It, Figure 8).

As a consequence of this arrangement of the several mutually engaging surfaces, there is no tendency for the clamping force to tilt" or' "cock the chaser in the holder, and a maximum frictional grip is provided. In this manner the chaser is held in place on the holder with the utmost security, and upon adjustment therealong, as is nwessary after grinding, isalways returned to the same relative position with respect to the holder, as far as the location of the cutting serrations is concerned, thus insuring accuracy and uniformity of performance of the chaser.

It will also be observed that the chaser has a relatively thickened edge adiacent'to the bevel It to resist the stress resulting from the pressure of clamp I. with this arrangement an unusually strong supporting surface is provided, and danger of damaging the chaserby "chipping or "breaking" at this point is greatly reduced and, in fact, practically eliminated.

Also, the provision of the fillet 2. adds considerably to the ability ofthe chaser to stand up under the clamping strains. This is due to the fact that incipient cracks resulting from hardening strains generally present at this point when the surfaces l4 and 22 are joined by an acute and sharp angle, as is the usual practice, are obviated. Thus, the tendencyof the chaser to break at this point is practically eliminated.

. The bevel 20 also serves a very useful purpose by preventing chipping" and "breaking", and

further provides a clearance space into which fine chips or cuttings may collect, thus permitting proper seating of thesurfaces l2 and 84. Furthermore, with this construction, slight wear in the cutter used to machine the surfaces" and 34 on the holder will not cause trouble in the later fitting of the chasers.

The clearance surface 22, which may take the slightly modified form 22a shown in Figure 5, in which corresponding portions of the chaser are designated by reference characters similar to those of Figures 2 and 3with the addition of the letter a makes it possible to machine the two surfaces l4 and-24, and Ma and 24a, with a combination cutter. This greatly facilitates the production of chasers and results in a considerable savings.

From the foregoing it will be evident that I have provided a novel and improved chaser and chaser holding means wherein the chaser is greatly increased in strength and durability and is held in place in the holder in a very positive and accurate manner.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is, therefore, to be considered in all respects as illustrative and not restrictive; the scope of the invention being indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. A chaser holder having a surface adapted to co-operate with the back seating surface-of a chaser, a second seating surface inclined with respect to said first named holder surface, and a clamp seating surface offset from and parallel to said second seating surface, said holder being provided with a threaded clamping screw bore having its axis arranged parallel to said flrstnamed surface.

2. In combination a chaser, a chaser holder and a chaser clamp means, said holder being provided with offset and parallel surfaces and having a seating surface; a chaser having a seating surface engaging said holder seating surface and a sec- 0nd surface engaging one of said offset surfaces, a clamping surface on said chaser, said second surface and said clamping surface being equally inclined with respect to said seating surface; said clamp means having seating surfaces engaging said chaser clamping surface and the other of said oflset surfaces; means to apply a force to said clamp means; said clamp seating surfaces and the surfaces on said chaser and holder co-operating therewith being inclined equally with respect to the line of action of said force whereby the resultant of said force is directed normal to and centrally of said holder and chaser seating surfaces.

3. A chaser comprising a body portion having a back seating surface; a second seating surface on said body, said last named seating surface being offset from and parallel to said back seating surface; a clamping surface inclined with respect to said seating surfaces and joined at one edge to said back seating surface by means of a beveled portion; an undercut surface joining the other edge of said clamping surface to said offset surface; said undercut surface extending a substantial distance beyond said first named edge of said clamping surface, and a base seating surface inclined toward said clamping surface, said base seating surface and said clamping surface making equal angles with said back seating surface.

4. A chaser comprising a body having cutting serrations thereon and provided with a clamping surface, a base seating surface, a. first back seating surface and a second back seating surface offset from and parallel to said first back seating surface, said seating surfaces being adapted to seat against corresponding holder surfaces, and. said clamping surface being adapted to cooperate with a corresponding clamp surface; said clamping surface and said base seating surface being inclined equally with respect to said back seating surfaces and toward each other, so that the resultant of a clamping force applied to said clamping surface in a direction parallel to said back seating surfaces acts centrally of and perpendicular to said back seating surfaces.

5. In a chaser holding device, a chaser holder, a clamp means and means to apply a force to said clamp means, two parallel and offset chaser back seating surfaces on said holder, a chaser base seating surface and a clamp engaging surface on said holder, said last-named two surfaces being inclined with respect to said back seating surfaces and parallel to each other, a chaser contacting surface and a holder engaging surface on said clamp means, and means for applying a clamping force to said clamp in a direction parallel to 88 said offset chaser back seating surfaces, said clamp surfaces being inclined equally with respect to the line of action of the force applied to said clamp.

CHARLES A. REIMSCHISSEL.

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