US2420572A

US2420572A - Tap grinding fixture

Info

Publication number: US2420572A
Application number: US640273A
Authority: US
Inventors: Laurence F Southwick; Rossiter R Holt
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-01-10
Filing date: 1946-01-10
Publication date: 1947-05-13
Anticipated expiration: 1964-05-13

Description

y 4 L. F. souTHwlcK Ei-AL I 2,420,572

TAP GRINDING FIXTURE Filed Jan. 10, 1946 3 Sheets-Sheet l FINVENTORS [4035x105- Saar/mack BY Ross/7Z7? A? Hou- ATTOEZVEY 35 M q EEFEPQ May 13, 1947. souf w c ETAL 2,420,572

I'AP GRINDING FIXTURE Filed Jan. 10, 1946 3 Sheets-Sheet 2 ATTORNEY y 13, 1947- I F. SOUTHWICK ETAL 2,420,572

TAP GRINDING FIXTURE Filed Jan. 10, 1946 3 Sheets-Sheet 5 II II I ENTORI [AUfiE/VG'f/FSOUTHMCK f fiassxrew/Rflur Z41 26 f2 ATTORNEY Patented May 13, 1947 TAP GRINDING FIXTURE Laurence F. Southwick, Mcriden, and Rossiter R. Holt, Manchester, Conn.

Application January 10, 1946, Serial No. 640,273

11 Claims. 1

This invention relates to abrading apparatus and more particularly to a tap-grinding fixture for grinding the forward end of a tap to any desired angle of chamfer and degree of relief.

One object of the present invention is to provide a tap-grinding fixture of the above nature having means to hold the tap in any desired eccentric position so as to permit the production of the desired chamfer by a grinding wheel engaging the tap.

A further object is to provide an attachment of the above nature having an inwardly-extending locating stud which is adapted to engage in the flute between any two adjacent lands of the tap for holding the tap stationary during the grinding of the point of a land thereof.

A further object is to provide an attachment of the above nature which may be used upon a lathe, surface grinder, tool grinder, hand grinder, or any other machine adapted to support a tap between centers, wherein one center is provided by the attachment and the other center is provided by said machine.

A further object is to provide an attachment of the above nature which is supplied with a longitud-inal shank for replacing'one center of the machine being used.

A further object is to provide a device of the above nature which will be simple in construction, inexpensive to manufacture, easy to install and manipulate, compact, precise, ornamental in appearance, having the minimum of backlash, and very eflicient and durable in use.

With these and other objects in view, there have been illustrated on the accompanying drawings two forms in which the invention may conveniently be embodied in practice.

In the drawings,

Fig. 1 represents a top plan view of a tap grindatta'chment embodying the invention.

Fig; 2 is a longitudinal sectional view of the same, taken along the line 22 of Fig. 1, looking inthe direction of the arrows.

Fig. 3 is a transverse sectional view, taken along the line- 3-3 of Fig. 1.

Fig. 4 is a detail sectional view showing the locating stud in operating position within one of the flutes of the tap, said section being taken on the-line 4-4- of Fig. 1.

Fig. 5 is a sectional View, taken along the line- '.i5 of Fig. 1 looking in a direction opposite from the view shownin Fig. 3.

Fig; 6- is a side view on a smaller scale of a modified form of the invention employing an angular carrier arm for holding the locating stud.

Fig. 7 is a rear view of the same, similar to the view shown in Fig. 5.

Fig. 8 is a front view of the same, similar to the view shown in Fig. 3.

Fig. 9 is a front elevation of the same.

Fig. 10 is a longitudinal sectional view of the same, taken through the barrel of the attachment.

In the first form of the present invention, the tap to be ground, which may have any number of flutes, will be accurately located by a radial stud which engages in a flute of the tap. The locatin stud is adjustably mounted within a side carrier arm which may be located at any one of several angular positions with respect to the barrel of the attachment, and will be held in operating position by a cap screw which is engaged in any one of a series of tapped holes in said barrel.

In the second form of the invention, the angular carrier arm is secured to the barrel by a single clamp screw, permitting the locating stud to engage in a flute of the tap adjacent the land being ground, or remote therefrom.

An important feature of both forms of the invention is the use of a rectangular pivotal center plate which supports the point of the tap at its center, and which may be shifted eccentrically about its pivot with respect to the center of rotation of the barrel of the attachment. The center plate is pivoted at one end on the barrel, and provided near its other end with an arcuate slot into which fits a cap screw for locking said plate at any desired eccentricity. When this center plate is shifted in one direction, right hand taps may be ground, and it will be oppositely shifted for left hand taps.

First form Referring now to the drawings in which like reference numerals denote corresponding parts throughout the several views, the numeral ID indicates a hollow cup-shaped barrel or head having a rectangular center plate [I pivotally mounted on a shoulder screw I I0 located in the forward closed end of said barrel. The center plate I!) is adapted to be held in adjusted position by a Washer Ilb engaged by the head of a clamping screw I la which is fitted loosely within an arcuate slot Ild.

The numeral ['2 indicates a longitudinal conical center which is carried by the plate 5-9, and the numeral l3 indicates a rearwardly-extending journal which has a tapered recess l-Ba toreceive a taper arbor (not shown).

Mounted upon the journal 13' isa split clamping collar [4 which is provided with a radial slot I la through which extends a headed locking screw [5 which is screwed into one side thereof for securely clamping the collar [4 upon the journal l3.

In order to locate the tap T in accurate position with respect to a grinding wheel 30, to be later described, provision is made of a longitudinal carrier arm I-B having a slotted section lBa for receiving a headed clamp screw 21, to be described later.

The free end of the carrier arm I6 is provided with a tapped hole for receiving a split bushing l9 which surrounds and clamps upon a radial locating pin or stud I! provided with a reduced rounded cylindrical tip Ila which is adapted to engage in a flute 32 of the tap T, at a point substantially opposite the land 33 being ground. The locating pin I1 is provided with a knurled clamping nut I8 which is fitted upon the bushing I9, the latter being provided with reversely tapered threads on its ends for fitting within the carrier arm [6 and the nut 18, respectively.

In order to limit the rotation of the barrel EB, provision is made of a radial stop pin 26 on the collar I4 and a longitudinal stop pin 2| secured rigidly to the rear end of said barrelsaid pins 20 and 2| being in alignment with each other.

The journal l3 is adapted to be fitted within an oilite bearing 22, which is tightly fitted over the end of said journal. The assembly is maintained in place by a retaining ring 23 fitting within a groove 28 formed in the barrel Ill.

Provision is also made of a steel washer 25 which presses a felt washer 25 against a shoulder 26a of the oilite bearing 22.

The other center of the machine is indicated by the numeral 28, and is provided with a fixed conical section 29 adapted to engage the rear portion 29a of the tap T.

The grinding wheel 30 is mounted upon a motor-driven spindle 1 3i and is adapted to be swun against the end of the land of the tap T for grinding it accurately to any desired angle of chamfer.

In order to permit the carrier arm l3 to be selectively secured in any one of four positions around the axis of the barrel l8, depending on the position of the land to be engaged by the locating stud, provision is made in the circumference of said barrel of four radial tapped

holes

34, 35, 3B, 3! adapted selectively to receive the clamp screw 21 therein.

Operation of first form In operation, the conical center l2 of the attachment will first be adjusted to the desired degree of relief by swinging the center plat H about the shoulder screw lie on which it is pivoted. The point P of the tap T will then be placed on the center [2 and the rear of the tap 25% will be engaged by the other conical center 29 of the lathe or other machine, as shown in Fig. l.

The locating pin I! will then he slid inwardly with respect to the carrier arm 16 until the locating tip I la thereof engages at the desired point of the flute 32 of the tap T.

The grinding wheel 3d will then be adjusted to any desired chamfer angle, after which it will be brought into cutting position by manipulating the cross feed (not shown) of the machine.

It will be understood that if desired, the an gle of chamfer may also be varied by shifting the axis of the grinding wheel 3!] or the center 29 of the machine. The periphery of the grinding wheel 30 may also be dressed to any desired angle.

The locating stud I! may then be used as a handle to rotate the barrel I0 and the carrier arm L6 as a unit until the land to be ground is brought into contact with the grinding wheel and is ground thereby to the desired extent. After the grinding of each land is completed, the locating stud II will be withdrawn and inserted within the next flute 32 of the tap T. This operation will be repeated until all the lands 33 of the tap have been ground.

One advantage of the present invention is that by limiting the movement of the barrel H] by the stop pins 20, 2|, the operator is prevented from swinging the fixture so far that it will damage the next adjacent land.

Modified form In the modified form of the invention, shown in Figs. 6-10, provision ismade of a dowel pin 50 for pivotally securing the center plate I I to the barrel ID. This form of the invention is also provided with a set of thrust ball bearings 52 to reduce the friction during the operation of the attachment.

More-over, instead of providing a straight carrier arm l6 for the locating stud I l, as in the first form of the invention, an angular carrier arm 53 having a slot 54 in its longitudinal section is employed. The arm 53 is adapted to be secured to the barrel I 0 by means of the clamp screw 27 which fits within a single tapped hole 55 in the barrel Ill.

The angular shape of the carrier arm 53 permits taps having two flutes as well as those having three or more flutes to be accurately located during the grinding of the points thereof.

The present invention is especially adapted for use in small machine shops, and is capable of performing efficient work with more accurate results than previous tap grinding attachments now on the market.

While there have been disclosed in this specification two forms in which this invention may be embodied, it is to be understood that these forms are shown for the purpose of illustration only, and that the invention is not to be limited to the specific disclosures, but may be modified and embodied in various other forms without departing from its spirit. In short, the invention includes all the modifications and embodiments coming within the scope of the following claims.

Having thus fully described the invention, what is claimed as new, and for which it is desired to secure Letters Patent, is:

1. In a tap-grinding fixture, a barrel, a support therefor, a center plate pivotally secured to the inner face of said barrel, said plate having a tapered center, means to swing said plate about its pivotal axis to vary the eccentricity of said center, a carrier arm rigidly secured to the circumference of said barrel and rotatable with said barrel as a unit, and a radial locating stud secured to said carrier arm and adapted to engage a flute of the tap being ground by a grinding wheel, said stud serving as a handle to rotate the tap eccentrically about the axis of the barrel so that the desired degree of relief may be obtained during the grinding of each tap land.

2. The invention as defined in claim 1, in which said center plate has an arcuate slot spaced from the pivot thereof, a stud mounted on the end of said barrel located in said slot, and a clamping screw for holding said plate in rigid position with respect to said stud.

3. Th invention as defined in claim 1, in which said carrier arm is mounted on an axis parallel to the axis of said barrel, and is slotted to permit adjustment relative to said barrel in a longitudinal direction.

4. The invention as defined in claim 1, in which said barrel is provided on its circumference with a plurality of tapped holes for selectively receiving a clamping screw for holding said carrier arm in adjusted position.

5. The invention as defined in claim 1, in which said barrel is mounted to rotate upon a bearing surrounding a journal which is secured to said support.

6. The invention as defined in claim 1, in which an anti-friction bearing is provided between said support and said barrel to reduce the friction thereof.

7. The invention as defined in claim 1, in which said carrier arm is angle-shaped so as to permit said locating stud to engage a tap flute adjacent to or remotefrom the land being ground.

8. In a tap-grinding fixture, a barrel, a support therefor, a center plate pivotally secured to the inner face of said barrel, said plate having a tapered center, means to swing said plate about its pivotal axis to vary the eccentricity of said center, a carrier arm rigidly secured to the circumference of said barrel and rotatable with said barrel as a unit, and a radial locating stud secured to said carrier arm and adapted to engage a flute of the tap being ground by a grinding wheel, said stud serving as a handle to rotate the tap eccentrically about the axis of the barrel so that the desired degree of curved relief may be obtained during the grinding of each tap land.

9. The invention as defined in claim 1, in which said locating stud is slidably mounted in said carrier arm whereby it may be quickly disengaged from the flute of said' tap.

10. In a tap grinding fixture, a hollow rocking barrel, said barrel carrying a radial locating stud for engaging a flute of the tap to be ground by a grinding wheel, a journal located within said barrel, a split collar clamped upon said journal, and coacting stop means on said barrel and said collar to limit th rotation of said barrel during the operation of grinding the point of said tap.

11. The invention as defined in claim 1, in which said tap locating stud has a bushing mounted thereon, the ends of said bushing being reversely threaded, the end of said carrier arm being screwed on one end of said bushing, the other end of said bushing being split and tapered and having a lock nut mounted thereon.

LAURENCE F. SOUTHWICK. ROSSITER R. HOLT.