US1469985A - Mechanism for grinding taps - Google Patents

Description

@ct. 9 W23.

J. BATH MECHANISM FOR GRINDING TAPS Filed Jan. 9, 1922 Patented Oct. 9, 19 3.

PATNT OFFIC.

JOHN BATE, 0F WORCESTER, MASSACHUSETTS.

mncnanrsra iron GRINDING mars.

Application-filed January 9, 1922. Serial No. 527,812.

This invention relates to improvementsv in mechanism for grinding taps.

It is the general object of my invention to increase the production of ground taps, to reduce the cost thereof, and at the same time to improve the quality of the product. An important feature of my invention relates to the provision of a grinding wheel for such purposes in which the edge of the wheel isformed with recesses or openings of substantial length, each opening being commonly fromone third to one half of the length of the adjacent cutting edge portion of the wheel.

Another object is to provide an improved device for effectively lubricating the wheel and work and for forcing the lubricant into the recesses of the wheel as they approach the work. This lubricating device is not specifically claimed herein but is presented in another application Serial No. 633,989, filed April 23, 1923 and which is in part a continuation of this application with respect to the lubricating 'devi'ce.

My invention further involves a method of operation in. which the teeth of the tap are Subjected to frequently repeated but intermittent grinding actions, with interposed cooling, lubrication, and removal of grinding dust and waste from the out. This method of operation is not claimed herein as y it forms the subject matter of a divisional application Serial No. 638,666, filed May 12, 1923'.

My invention also relates to arrangements and combinations of parts which will be hereinafter described and more particularly pointed out in the appended claims.

A preferred form of 'my invention is shown in the drawin s in which Fig. 1 is a partial side elevation of my improved grinding wheel and the device for the line 3-3 in supplying lubricant thereto, the work shown in section;

Fig. 2 is an edge view of the grinding wheel, partly in section, and

Fig. 3 is a sectggnal plan view taken along Referring to the drawings, I have shown the threaded work in the form of a tap T of a usual type positioned adjacent a inding wheel 10. It will be understoo that the tap is mounted upon centers to rotate at being a comparatively slow speed about its axis in the direction of the arrow a 1n Fig. 1.

The grinding wheel 10 rotates in the direction of the arrow 6 in Fig. l at a com paratively high speed. The cutting edge of the grinding wheel 10 is preferably formed substantially as shown in section inFig. 2, the extreme outer or cutting portion 11 being shaped to correspond to the particular type of thread to be round and projecting outward from the b0 y of the wheel, as indicated. The cutting portion 11 is also preferably provided with straight parallel side portions 12 for a purpose to be described.

A very important feature of my invention consists in providing openings or recesses 13 in the edge portion 11. of the wheel. These openings are of substantial length and, as shown tween one third and one half of the length of the adjacent edge portion of the wheel. It will be understood that these proportions may be varied within rather wide limits.

n the preferred form of my tap grinding mechanism, I also provide a pipe 15 by which lubricant is forcibly supplied to the grinding wheel and to the work being ground. The'lower end of the the side adjacent the wheel 10 with a slot or opening 16. The pipe is positioned so that the cutting edge 11 of the wheel will project through the slot 16 into the interior'of the pipe 15 and directly into the stream of oil or other lubricant which is forced through the pipe. The straight side portions 12 of the wheel permit the is provided in the drawings, each opening is be-v pipe 15 on lit) pipe 15 than-would be otherwise possible,

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and the pipe protects the edge of the wheel from injury. lit is also possible to around its circumference and consequently about one hundred short cutting sections of the grinding wheel edge will engage each toothed portion of the tap.

Several important advantages arise from the provision of the openings in the grinding wheel edge, particularly when associated with my improved device for conveying lubricant thereto.

The manufacture of ground taps and other threaded work from high speed steel is a comparatively recent development in the art and serious diiliculty has been encountered in producing such work, as it is necessary that they shall be extremely hard in order to utilize the advantages of the steel. lit will be noted that in grinding the thread, the wheel is engaged along each side of its edge portion 11 and the engaged or grinding surface is thus of considerable width. I

In the use of the ordinary grinding wheel, the wheel remains in close grindin contact with the teeth for the entire period required for grinding each tooth. The grinding operation necessarily generates heat and this continuous contact causes the generated heat to have an accumulative effect on the it is found by inspection and test that teeth thus ground become softer toward the rear end of each tooth portion, the temperature of the teeth being gradually raised as the grinding operation continues. This softening of the metal commonly occurs only in the extreme outer surface or skin of the work, but is nevertheless suficient to seriously impair the cutting qualities thereof.

With my improved grinding wheel. particularly when associated with my improved lubricating device, li am able to grind the teeth or threads without raising the temperature thereof sufhciently to etl'ect the temper. llnstead of maintaining continuous grinding contact with the work, T subject the work intermittently to frequently repeated grinding actions and in the interval between these actions I flood the work with lubricant which is forced into the recesses 13 or the wheel and is forcibly messes carrier through the thread of the work by the rotation of the Wheel.

This application of lubricant has a direct action in cooling the metal and in removing all waste or dust from the cut and also reduces the heating efiect of the wheel by thoroughly lubricating the surfaces to be ground.

The passage of the edge of the wheel into and through the end f the pipe 15 .also has an important edect in forcing the lubricant into the recess 13 and in filling the pores. or openings of the wheel with lubricant, at the same time removing any dust or waste therefrom.

This arrangement of mechanism and method of procedure not only enables me to prevent softening of the metal during the grinding operation, but also largely increases the production, as the grinding speed ma be increased without heatin the work. It 18 also found that a wheel wild out much faster and freer when provided with the openings 13 as shown in Fig. 1. Each separate grinding portion of the wheel apparently makes a fresh cut as itpasses through thework and the combined results of these numerous fresh cuts is found to be substantially greater than the results which would be obtained by a wheel having a continuous contact with the work.

It may also be noted that the recessed edge of the wheel has a certain fan effect which also tends t cool the wheel and work. Different kinds of oil or other lubricant may be used with my improved mechanism but I have found that for high speed steel the best results are obtained by the use of a ery high grade oil and particularly with sperm oil. While I have shown my invention as particularly applied to the production of ground taps, important advantages thereof may be utilized in the production of-continuous ground screw threads and other similar articles and such use of my invention is to be considered within the scope of my protection.

Having thus described my invention, it will be evident that changes and modifications can be made therein by those skilled in the art within the spirit and scope of my invention as set forth in the claims, and I do not wish to be otherwise limited to the details herein disclosed, but what ll do claim is 1. lln a machine for grinding threaded work, the combination of a wheel formed of abrasive material and having its cutting edge shaped to correspond to the desired thread space, and means to flood the work and wheel with lubricant at the cutting point, said wheel having a series of transverse openings around its cutting edge by which lubricant is carried into the thread spaces and the adjacent parts or the threads are alternately ground and cooled at rapidly each of substantial length,. the length of a repeated intervals. cutting edge portionbeing between two and 2. As an article of manufacture, a wheel three times the length ofthe adjacent open- 1 for grinding taps having its working edge ing. 5 shaped to correspond to the thread to be In testimony whereof I :have h'ereunto ground, and comprising alternately disposed affixed my signature. cutting portions and transverse openings 7 'JOHN' BATH.

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