US1617122A

US1617122A - Method of making screws and bolts

Info

Publication number: US1617122A
Application number: US54953A
Authority: US
Inventors: Kaufman Charles
Original assignee: Individual
Current assignee: Individual
Priority date: 1925-09-08
Filing date: 1925-09-08
Publication date: 1927-02-08
Anticipated expiration: 1944-02-08

Description

1,617,122 J c. KAUFMAN METHOD OF MAKING SCREWS AND BOLTS Filed Sept. 8, 1925 Inven' l Km M MW Patented F eb. 8,1927;-

UNITED STATES CHARLES KAUFMAN, or CLEVELAND, 01110.

METHOD OF MAKING SCREWS AND BOLTS.

7 Application filed September a, 1925. Serial m. 54,953.

This invention relates to a method of making certain kinds of screws and bolts having. an unthreaded portion next to the threads, such as cap screws, machine bolts,

form the blanks that they are held to exact dimensions, and so that thycan' be formed in any lengths desired, and at the same-time permit a better and larger head to be formed which does not crystallize or fracture in forming. Y

These screws and bolts are commonlyformed from a length of wire of a diameter corresponding to the pitch diameter of the thread to be formed, and by means ofdies a portion of the blank is upset to form the head and also to form an enlarged portion between the head and the portion tobe threaded, said enlarged portion being expanded by the upsetting process to the external diameter of the threads which are to be rolled onto that portion of the blank which remains at the original diameter.

Instead of starting with ablank which is of the pitch diameter of the thread to be formed, and then upsetting the stock to enlarge the same to form the unthreaded portion and the head, I start with a length of stock which in diameter corresponds to the diameter of the unthreaded portion of the finished .screw or bolt, and reduce that portion of the blank which is to be threaded, the part to bethreaded being reduced to the pitch diameter of the thread to be formed. Preferably the reducing of the part to be threaded is accomplished in the same dies and at the same time that the other end of the stockis upset to form the head. a

The invention may be further brieflysummarized as consisting in the steps of the improved method which will be described in the specification and set forth in the appended claims.

In the accompanying sheet of drawings, Fig. 1 shows a length of wire ready for the forming process; Fig. 2 shows the blank after the stock of Fig. 1 has been treated by my improved method; Fig. 3- shows the finished screw, in this instance a cap screw; and Fig. 4 shows diagrammatically a pair of dies which may be utilized in carrying out my improved method.

The screw which is produced is of con- 'ventional shape or design, and consists of a head 10,-a threaded portion 11 and an unthreaded portion 12 between the head and threaded portion. If the threads are formed by a rolling process, as is customary, the portion 12 must beof greater diameter than the portion to be threaded, and as before stated, the head 10 and portion 12 are generally formed by expanding the stock, the

original diameter corresponding to the pitch diameter of thethreaded portion.

Inasmuch as the head 10 and unthreaded portion 12 are by the commonly employed method both formed by expanding or enlarging the stock, practice has demonstrated that the length of the unthreaded portion is limited, i. e. can not be made in more than a predetermined length for a given size of stock, and inasmuch as the head is formed from a stock of relatively small size, it is generally not perfectly formed and often crystallizes or fractures in the forming.

According to my invention I start with stock or length of wire indicated at 13 in Fig. 1, and produce the blank shown in Fig. 2, by a method wherein'the diameter of the portion 15 to be threaded is reduced, while the enlargement 16.to form the head of the finished screw is formed by upsetting the stock of the original diameter. That is to say, if D represents the diameter of the stock 18, this diameter is maintained in the portion 14, while the portion 15 to be threaded,.is reduced to a smaller diameter d, and the head portion 16 is upset to a, larger diameter D.

In carrying out the method I prefer to use :male and female dies, indicated convention- In practice the wire is fed in an indeterminate len h from a suitable reel, and is automatica ly cut into sections of the desired length, and asa section of stock is cut off it is carried over into line with the cavity of die 17, which is the stationary die. The

die 18 reciprocates, and as soon as the stock comes into line with the cavity it is struck by the die and driven inward, a portion of the stock being forced into the reduced part 17 of the cavity so as to form theportion i of the blank by reducing the diameter of I At the same time that the stock is form orpartially form the head 16. The

blank is head may be entirely formed by this same blow of the die or plunger 18, but generally the stock is given a second blow to complete the formation of the head, after which the blank is ejected. I

"By this method the reduced part 15 of the iven a skin or surface hardening character stic of drawn or extruded material, which makes it very desirable for screw forming purposes, and inasmuch as, the portion 14 retains its original diameter, it is, of course, possible to make this of any length, as is true also of the reduced part 15. On the contrary, by the old method wherein the diameter of the portion 14 is formed by the upsetting process, the length of the unthreaded portion of the blank is limited. Furthermore, since the diameter of the portion 16 'is unchanged, and the portion 15 formed by driving the stock into the reduced part of the die cavity, it is obvious that the blanks can be turned out, one after another, with the portions 14 and 15 held to the exact dimensions desired, which is not always the case with the prior process, and since the head 16 is formed from stock of a larger diameter than is used with the old process in forming a given sized screw, thereis less likelihood of crystallization and fracture in forming thehead.

In brief,'therefore, by my method above described, I am able to produce better and more accurate screws or bolts than heretofore, with a. minimum loss on account of defective blanks, and with any desired length of unthreaded portion, and at the same time'the blanks can be produced with the same or greater rapidity than by the prior .methods. After the'blank described above, and illustrated in Fig. 2, is formed, the screw is fi'nished by converting, by the usual process,

the annular head 16 to an octagonal or other the reduced portion and. the enlarged head polygonal shape des ed if th type of screw requires it, and by forming the thread 11 on the reduced part-.15 of-the blank, generally by rolling the thread thereon.

As already stated, the stock from which the screws areforlned corresponds in size to the diameter of the unthreaded portion, but the stock may have a slight oversize or undersize tolerance. If it is slightly oversized, the stock will be forced into the die-cavity by the plunger 18 slightly reducing thestock to the amount of the tolerance to form the portion 14: of theblank. If the stock is slightly undersized, the stock is slightly enlarged to completely fill the portion 17 of the die cavity. Generally the original diameter D of the stock is maintained in the portion 14 of, the blank, but as stated above,

a slight variation in the size of the stock, either oversize orundersize will have no material effect on the method since the most important feature of the invention is the reduction and lengthening and consequent hardening of that part of the stock which is to be threaded. x

While I have illustratedmy method applied to the production of cap screws, it can be used just as effectively for forming other types of screws and bolts such as those mentioned in the early part of the specification. While I have described the preferred method of carrying out my invention,I do

not desire to be confined to the precise details shown, but aim in my claims tocover all modifications which do not involve a departure from the spirit and scope of my invention. a

Having described my invention, I claim: 1. The method of making screws and bolts, which comprises upsetting one end of a length .of stock to form the" head-portion and in the same operation drawing out and thereby lengthening and reducing another portion to the pitch diameter of the thread to be formed by forcing the stock endwise into the opening of a drawing die, and forming the thread on said portion.

' 2. The method of making screws and bolts, which comprises forcing a piece of stock w by pressure exerted endwise thereon into the opening of a drawing die to drawout and thereby reduce and lengthen the portion which is to be threaded, and in the same operation upsetting upon one end an enlarged head portion, and thereafter 2 forming the thread on said-reduced portion.

3. The method of making screws and bolts which comprises forcing a piece of stock by pressure exerted-endwise thereon into the opening of a drawing die to draw out and 5 thereby reduce. and lengthen the portion .which is to be threaded, and in the same operation upsetting upon one end an enlarged head portion and retaining a portion between portion of substantially the same-diameter as the diameter of the iece of stock, and thereafter forming the t read upon the re; duced portion.

4. The method of making screws and bolts, which comprises forcing a piece of stock by pressure exerted endwise thereon into the opening of a drawing die to draw out and thereby reduce a portion to a diameter substantially equal to the pitch diameter of the thread to be formed, and in the same operation upsetting an enlarged head portion upon one end, and retaining a portion between the reduced portion and the enlarged head portion of a diameter substantially equal to the diameter of the piece of stock, and thereafter forming the thread upon said reduced portion.

5. The method of making screws and bolts,

whieh comprises forcing a piece of round wire or rod by pressure exerted endwise thereon into the opening of a drawing die to draw out and thereby reduce the portion to be threaded and in the same operation upsetting an enlarged head portion upon one end but retaining an intermediate portion of a diameter substantially equal to the diameter of the wire or rod, and thereafter rolling a thread upon said reduced portion.

In testimony whereof, I hereunto atfix my signature.

CHARLES KAUFMAN.