US2757457A - Center punch - Google Patents

Description

CENTER PUNCH Albert R. Ziegelski, Sr., Chicago, Ill. Application llanuary 18, 1955, Serial No. 482,523

2 Claims. (Cl. 33-139) This invention relates to a novel center punch of superior form and construction and more particularly is concerned with locating center punch marks corresponding to the aXis of a templet hole having a cylindrical wall.

Center punches having various shapes and sizes have long been known in the art and most of these prior art devices have attempted to provide some method for adapting a single center punch for use with a plurality of different hole sizes. Generally this has been accomplished by mounting a cylindrical punching rod or bar within a tubular sleeve, and the centering end of the sleeve has been tapered to permit the sleeve to perform its centering function for a range of hole sizes.

ln practice such devices have exhibited certain inaccuracies and this is particularly true in the case of holes of cylindrical shape. Such errors are further aggravated in those instances in which the templet member is extremely thin as this often makes it impossible for the tapered centering surface of the guiding sleeve to properly engage the periphery of the templet hole.

Due to the decreased tolerances permissible in modern machines and structures, accurate center punches have become even more important, and in an eifort to eliminate the inherent defects of a tapered centering surface, center punches having an additional guiding and centering member have been devised. Even in these instances the center punches have not been completely reliable and accurate.

ln many instances there is a minimum of clearance adjacent the hole that is to be punched, and hence it is important that the center punch be no larger than the bolt that is to be inserted in the hole. No known center punch meets this specification, and in the case of those punches that are provided with additional guiding and centering members for improved accuracy, clearance difficulties are even more pronounced. The clearance probd States Patent O lem arises most frequently in the automobile eld though t it is by no means limited thereto.

lt is the principal object of the present invention to provide a center punch of simplied design that overcomes the defects of the prior art devices. Accordingly, it is proposed to provide a center punch of maximum accuracy that closely conforms to the size and shape of the bolt to be used so that its use is not impaired by small clearances adjacent the point of application.

This is accomplished by combining a plurality of tubular centering members representing a range of hole sizes with a single punching bar that is adapted to be telescopically received by the individual centering members.

It is additionally proposed to set up a minimum amount of friction between the guiding sleeve and the punching bar sucient to maintain the parts in assembled relationship but also adapted to permit relative sliding movement when the punching bar is subjected to a marking blow.

Other objects and advantages of the invention will be apparent during the course of the following description.

ICC

In the accompanying drawings forming a part of this specification and in which like numerals are employed to designate like parts throughout the same,

Fig. 1 is an exploded perspective view illustrating the manner of applying the center punch;

Fig. 2 is a front view of an assembled center punch;

Fig. 3 is a sectional view illustrating the center punch applied to a templet for marking a main frame member; and

Fig. 4 is a sectional Fig. 3.

Center punches usually find application when it is desired to bolt a pair of structural members together, one of lwhich is already formed with bolt holes. It is standard practice to appropriately position the two members relative to each other so that the bolt holes in one of the members may assist in locating the center points for the holes that are to be drilled. p

Referring to the drawings and particularly to Fig. l, the member that is to be center punched is designated 10 and is hereafter referred to as the main frame member, and the member that is already formed with holes is designated 12 and is `hereafter referred to as a templet member. The templet member is illustrated with a pair of bolt holes 13.

The center punch itself consists of a guiding sleeve 14, a punching bar 15,` and a split ring 16. The guiding sleeve is formed with a cylindrical inner bore and a cylindrical outer surface that is concentric with the bore. The major portion 19 of the cylindrical outer surface is smooth and is adapted to cooperate with the cylindrical side walls of the templet holes, and the minor portion 2d of the cylindrical outer surface is knurled to facilitate handling. The guiding sleeve 14 is arranged so thatits outer diameter is substantially equal to the diameter of the templet holes but is suthciently smaller to permit the smooth annular end portion 19 `to be telt-:scoped within the holes. The cylindrical bore 18 is of substantially the same size as the punching bar 15 and is adapted to telescopically receive the punching bar for relative longitudinal sliding movement.

The punching bar 15 is formed with a pointed marking end 22 and a lat surfaced striking end 23, and its main surface portion 24 is of a substantially smooth cylindrical shape. It is formed with a knurled surface 25 adjacent the striking end 23 to 'facilitate handling. In addition, the punching bar `1S is formed with an annular groove 26 that is adapted to receive the split ring 16.

The diameter of the main surface 24 of the punching bar is slightly less than the diameter of the cylindrical bore so that the punching bar tits nicely Within the cylindrical bore 18 and is adapted to slide relative to the guiding sleeve. The split ring 16 is slightly larger. than the annular groove 26 so that it projects slightly above the smooth cylindrical surface of the punching bar to resist any relative sliding movement. This resistance of thetsplit ring is sucient to prevent sliding movement due to the weight of either the guiding sleeve 14 or the punching bar 15 but does not in any way impair the desirable sliding movement which is occasioned by hitting the striking end 23 with a` hammer or other suitable implement. The split ring feature greatly adds to the convenience of the device and permits the center punch to be used in an inverted position without` becoming disassembled.

In applying the novel center punch, the templet member 12 is positioned on the main frame member 1t) in order to determine the desired location for the bolt holes which are to be drilled in the main frame member. The center punch is then inserted in one of the templet holes 13, as shown in Fig. 3, so that when the striking end 23 is hit, the pointed end 22 of the punching bar will accurately mark the center point of the hole to be drilled.

View taken along the line 4-4 of It will be noted that the punching bar and sleeve are assembled with the pointed end 22 of the punching bar facing out of the smooth surfaced cylindrical end portion 19 of the guiding sleeve and the smooth cylindrical end surface portion 19 is adapted to y'cooperate with the cylindrical wall 28 of the bolt hole 13. Since the sleeve closely matches the size of the bolt hole and since the punching rod closely matches the size of the cylindrical bore 18 of the sleeve, the center point for the hole to be drilled is accurately defined with respect to the templet hole.

The center punch may be used with templets of varying thickness, the only limitation being the length of the smooth cylindrical surface portion 19, and the center punch is particularly effective in the case of extremely thin templets. There are certain applications wherein the templet consists of shim stock that may have a thickness ranging from .015 inch to .001 inch and it has been found that the present center punch is able to more accurately locate the center marks because the smooth surfaced cylindrical end portion of the guiding sleeve cooperates with the cylindrical wall of the templet hole in exactly the same manner irrespective of the thickness of the templet.

It will be noted that the center punch of the present invention very closely corresponds to the size and shape of the bolt that is to be inserted to secure thel templet member to the main frame member, and when one considers that in the automotive iield particularly the clearances between adjacent bolts' and other structural members are sometimes quite small, it will be appreciated that this is a very important feature in a practical center punch. It should be apparent that this center punch may be employed in any locations where it is possible to install a bolt.

In order to adapt the present center punch to various hole sizes, it is proposed to employ a plurality of sleeves with a common punching bar. Accordingly, all the sleeves must have bores of equal diameter that correspond to the diameter of the punching bar. In actual practice, however, the range of bolt hole sizes is best handled by employing a plurality of punching bars. Thus, for bolt holes ranging from 1A inch to 1/2 inch in diameter, it is proposed to employ a punching bar having a diameter of 1A; inch with a plurality of sleeves having outer diameters ranging from 1A inch to 1/2 inch. It is preferred that the outer diameters of the sleeves increase in sixteenths of an inch. For bolt holes ranging from 9/16 inch to 1 inch in diameter, it is proposed to employ a punching bar having a diameter of 1A inch with a plurality of sleeves having outer diameters ranging from W18 inch to 1 inch, the sleeves being stepped in degrees of 1A@ inch. For bolt holes ranging from 11/16 inches to 2 inches in diameter, it is proposed to employ a punching bar having a diameter of 1/2 inch with a plurality of sleeves having outer diameters ranging from 11/16 inches to 2 inches, the sleeves being stepped in degrees of 1/16 inch.

It is proposed to furnish all of the above combinations of center punches and guiding sleeves ina single kit to provide a unit capable of handling nearly all hole sizes that are encountered in practice.

Thus the objects of the present invention have been accomplished in that a novel center punch of extremely high accuracy has been provided. The accuracy arises from the cooperation between the smooth cylindrical surface provided at one end of the guiding sleeve and the cylindrical wall of the templet hole. In addition, the

present center punch closely conforms to the size and shape of the bolt that is to be installed and thus may be used in substantially any location that is adapted to receive a bolt.

It should be understood that the description of the preferred form of the invention is for the purpose of complying with Section 112, Title 35 of the United States Code.

I claim:

1. A center punch device for use in locating center punch marks on main frame, said marks indicating the axial center lines of parallel-walled cylindrical templet holes of various sizes, said device conforming to the clearance requirements of a bolt size corresponding to the hole size to be marked and comprising in combination: a plurality of elongated cylindrical tubular sleeves of equal length, there being one sleeve for each templet hole size, each sleeve having centering means consisting of a smooth paralle1-walled cylindrical surface portion at one end thereof of substantially the same co1 iguration as the corresponding cylindrical templet hole and cooperating with the walls defining said templet hole to center said sleeve in said corresponding templet hole, each sleeve having a bore extending longitudinally therethrough, the bores in each of said sleeves being identical', and a single punch slightly greater in length than said sleeves having a pointed marking end and a striking end and the diameter of the punch is slightly less than that of the sleeve bore, said punch having a split ring substantially iilling a circumferential groove formed in an outer surface portion thereof, said split ring being slightly larger in cross section than said groove, the surface defining said bore and the outer surface portion of said punch being complemental in size and shape and the pointed marking end of said punch being located relative to the cross section of said punch such that when said punch is positioned within the bore of one of said sleeves with the marking end of said punch adjacent the smooth cylindrical surface portion end of said one sleeve, said pointed marking end coincides with the axial center line defined by said smooth cylindrical surface portion of said one sleeve and the split ring prevents relative sliding movement between said punch and said one sleeve due to the weight of either the punch or the sleeve.

2. A center punch device as called for in claim 1 and wherein each of said bores is cylindrical and is concentric with the smooth parallel-walled cylindrical surface portion of its sleeve and wherein said punch has a cylindrical outer surface portion.

References Cited in the tile of this patent UNITED STATES PATENTS 804,795 Cummings Nov. 14, 1905 824,867 Houghton July 3, 1906 837,690 Labunski Dec. 4, 1906 911,608 Pullen Feb. 9, 1909 1,233,458 Fisk July 17, 1917 1,761,207 Guertin lune 3, 1930 2,426,480 Wood Aug. 26, 1947 2,480,399 Dolascr Aug. 30, 1949 2,492,367 Oprescu Dec. 27, 1949 2,590,585 Temple Mar. 25, 1952 2,633,644 May Apr. 7, 1953 OTHER REFERENCES Page of American Machinist, April 29, 1943.

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