US2928528A

US2928528A - Wire-drawing die

Info

Publication number: US2928528A
Application number: US434034A
Authority: US
Inventors: Roy M Kelday; Frederick L Hayden
Original assignee: Steel Company of Canada Ltd
Current assignee: Steel Company of Canada Ltd
Priority date: 1954-06-02
Filing date: 1954-06-02
Publication date: 1960-03-15
Anticipated expiration: 1977-03-15
Also published as: AT212249B; DE1132081B; US3158258A

Description

R. M. KELDAY EI'AL 2,928,528 I March 15, 1960 WIRE-DRAWING DIE 5 Sheets-Sheet 1 Filed June 2, 1954 N M 3 22% N.K*R wMm m mrm 7 m A 3 v 6 March 15, 1960 R. M. KELDAY ET AL 2,928,528

WWWWWWWWWWWWW IE March 15, 1960 R. M. KELDAY- ET AL WIRE-DRAWING DIE 5 Sheets-Sheet 3 Filed June 2, 1954 Z w Z. m -M2 w m A rm March 15, 1960 R. M. KELDAY ETAI.

WIRE-DRAWING DIE 5 Sheets-Sheet 4 Filed June 2, 1954 INVENTORS Ra y M Kn. DA Y FRE'DR/CKZ. HA YDN A Tree/vs vs United States EwDRAWING DIE Application June 2, 1954,.SerialN0. 434,034l' 2 Claims. (Cl. 205-49 This invention relates to new andusefulirnprovements in the production of cold drawn (hereafter, usually merely termed drawn) wires, rods, bars and similar solid elongated drawn metal products, particularly where the metal is steel. The term wire will'hereafter in this specification and claims he used in certain instances which will be obviousfrom the context, to, designate all such drawn metal products collectively. The invention aiso relates to articles made from wire, particularly steel wire, e.g. nails, spikes, and other driven fastening devices, concrete reinforcement, barbed wire and non-skid gratings.

Wire of which the general'cross-sectional shape is uniform and uniformly oriented along the length of the wire. (hereinafter termed conventional wire), can at presentbe drawn insubstantially any desired cross-sectionai shape. Drawing effects a substantial cold working and a reduction in cross-sectional area of the wire, and drawn conventional wire exhibits throughout its structure and over its whole surface'cold drawn characteristics, which are more uniform the more nearly the general cross sectional shape of the wire is circular. In conventional drawn steel wire, the grain flow lines canlbe seen to be uninterrupted and to lie Wholly in planes which include the longitudinal axis of the wire, though they are not easily detectable in the case of metals other than steel. No practicable way has so far been devised of drawing wire which is other than conventional, for example of drawing helical wire, i.e. wire having a general crosssectional shape which is non-circular and of which the,

orientation varies helically along the length of the wire. Heretofore, for a great many years, helical wire articles have in practice been producedin one of three ways, all

involving special operations'on conventional drawn wire.

One way, used in the manufacture of so-called threaded noncircular cross-section aboutits longitudinal axis. The

first two ways of helixing are essentially batch as opposed to continuous operations, and all involve verysubstantial expense, with the result that, for example, the cost of threaded nails is very substantially greater than that of comparable ordinary nails. Moreover, the rolling operation tends to alter at least the desirable surface structure imparted to the article by the cold drawing, with the resultzth'anforexample, it no longer exhibits cold drawn atent 2,928,528 7 Patented Mar. 15,1960

'ice

characteristics over its whole surface; The twisting operation, furthermore, canbe carried out only onrelatively soft wire; it sets up torsional stresses in the article and mentionedv extreme practical diiticultyv of satisfactory maintenance; the fact that uniformityin the product is not achieved since itisnever practically possible to ensure that all the cutters or rollers act evenly ontthe wire'ythe' fact that ragged edges-are apt to be'produced along the crests of the helices; and the fact that only, indented shapes, such as crosses, 'as distinct: from straight sided shapes,,such.as squares; or convexlycurved shapes could in any-event be-made. Devices'of this type have apparently been constructed and experimented with. but appear never to have gone into practical 'coinmercia'luse. Other. proposals have included the continuous twisting ofconventional wire-of non-circular cross-section; the drawing of wirethrough a die having 'a straight passage with a general cross-sectional shape other than circular andpositively rotating the die to twist thewire between'the die and the drawing block; and the drawinguof wire through apositively rotated die having; apassa'ge of circular cross-section which becomes non-circula'r for avery short distance just at theexit, whereby it issug'gested, ahelixnisimpressed on therwire-without twisting it; None of these other proposals appears ever to have been-pram tically used, and the practicalart remains today essentially as ithasstood for fifty years or'more;

- Accordingto the present invention, wire is very easily andsatisfactorily drawn, shaped and helixed in a'singl'e operation by drawing it through a-rotatable' die havinga passage of which thegeneral cross-sectional shape is non-= circular over at least a substantial part of. its I working length and which is.helically'twisted about its'ilongitudinalaxis throughout the portion of non-circularcross=sectional shape. i

it was proposed atleast as long as seventy-five yea'is v ago, though apparently without leadinglto any'pr'actical use, that the surfaces of lengths: of thin'tubular and even solid stockrmight be ornamented, without appreciablyre ducing orotherwise aIte'ringJtheir cross-section, by pass ing themthrough a. freely rotatable die having a passage of circularcross-section with parallel alternating shallow ribs and grooves formed on its wall and extending atanangle to its longitudinal axis. The object of these proposals was to produce decorative helical fiutings on .the'

. wire is referred to orientation in such planes is-meant.)

The cross-sectional shape or area or both,.may,jmorea According to the invention wire is,- in a single over, be made different at different points along the length of the wire.

Wire produced in accordance with the invention, drawn with a general cross-sectional shape which is non-circular andof which the orientation is different at different points along the length of the wire, has all the desirable qualities of conventional drawn wire. -lt exhibits cold drawn charaeaspae acteristics throughout its structure and over its whole surface and is substantially free'fr'orn torsional stresses, such torsional stresses-as it may have being merely those which arise from coiling and are found in conventional drawn wire. The grain fiowjlines, where detectable, are substantially uninterrupted and lie substantially 'wholly'in planes including the longitudinal axis of the wire. It does not exhibit the striations or-roll orvibration marks at right angles-to the helix, the roughening along the valleys or indentations along the crests defining the helix, or the 7 surface flaking to befound in wire articles inwhich helical grooves have been rolled.

The'cross-sectional shape of wire produced according to the invention may be uniform along the length of the wire with its orientation varying helically' along that length, or the cross-sectional shape or area or both may be different at different points along the lengthof the wire." Wire of which the cross-sectional shape is uniform along its length is sometimes referred to hereinafter as wire of simple form, and wire of which the cross-sectional shape or area is different at different points along its length is sometimes referred to as hereinafter as wire of complex form. In the case of wire of simple form, thei helical variation of its shape is of uniform lead along the length of the wire, and the cross-sectional shape and area is uniform along that length, though special steps may be taken controllably to vary the lead along the length of the wire. 1 a v 1 v Many products of desirable characteristics are produced from wire made according to the present invention. 'Ihus, improved barbed wire may be produced from wire a made according to the invention of simpleform, and irn-" diminishes in cross-sectional area over a substantial part of its working'length (i.e. that part of the passage with which thewire comes into contact While being drawn), but in a die according to the invention the whole part of the working length of thepassage which is of non-circular crosssection';is.-.helically twis ted about its longitudinal axis. While a die for'the drawing of conventional wire of non-circular cross-section is fixedly mounted in the drawingjapparatus, a die according to the invention is mounted so that it is permitted to rotate-about its longitudinal axis but is prevented from moving along that axis.

To obtain any drawing at all, it is of course necessary, as in the drawingof conventional wire, that the maximum radial dimension of, the wire be greater than at least the minimum radial dimension of the passage at its effective cross-section (i.e. the minimum cross-sectionwhich determines the cross-section of the drawn wire); By the term maximum radial dimension is meant the radius of wire of which the minimum radial dimension is greater than the maximum radial dimension of the effective crosssection of the die passage. If the general cross-sectional shape of the wire to be drawn is circular, a drawn wire of simple shape will be produced ,even when the radius of the wire is smaller'than the maximum radial dimension of the effective cross-section=of the diepassage. A drawn wire of complex form may be produced according to the invention by drawing through a die according to the invention a wireof which the general cross-sectional shape is non-circular and of which the minimum radial dimenson is smaller than the maximum radial dimension of the effectve cross-sectiono'f the die passage, orby drawingthrough a die having a passage of which the general cross-sectional shape is non cir cular, a wire according to the invention'ofi simpleforfm and of which the minimum radial dimension is smaller than the maximum radial dimension of the, effective cross-section of the pas:

sage. 'The die passage may .be helically twisted in the opposite direction to the helixing of the wire. Theinvention will be more fully described by reference I to theattached drawings, in'which:

the invention,

Figure '2 is a face view, partially diagrammatic, from the entry-side of one form of die according to the invention with a passage of square cross-sectional shape,

Figure 3 is. a'longitudinal section .on the line 3--3;

ofIFigureZ, t

Figures 4 and 5 are cross-sections on the lines 4 -4 and 5-5 respectively of Figure 3, s Figure 6 is a face view from the entry side of another form of die according to the invention,

Figure? is alongitudinal section of the line 7-7 of Figure 6,

Figures 8, 9 and 10 are cross-sections on the lines 8-8, 9.--9 and 10-10 respectively of' Figure 7,

Figure 11 is a face view of a die according to the in-' vention similar to that shown in Figure 2, except that the cross-section of the passage is oval,

Figure 12 is a diagram illustrating the terms maximum radial dimensionand minimum radial dimen-,

Figure 15 is a cross-section onan enlarged scale of the wire of Figure 14,

Figure 16 is a perspective view ofan example of a wire of complex form'according ,to the invention,

Figure 17 is' a cross-section on the line 17-17 of Figure"16,,- 1 i Figure 18 is a perspective view of another example of a wire of complex form according to the invention,

Figure19 is, a cross-section along the line 19-19 of 1 if Figure 18, i

Figure 20 is a perspective view of a further example of a wire, of complex form according to the invention, and i Figure 21 is a cross-sectionon the line 21-41 of,

Figure 20. A

the smallest circle centered on the longitudinal axis which i can be circumscribed about the cross-section of the wire (or passage) and by the term minimum radial dimension is meant the, radius of the largest circle centred on the longitudinal axis which can be inscribed within the According to Figure 1 illustrates, by way of example, one form of apparatus for practising the invention. In this apparatus the base 1 has a transverse wall 2 near its rear formedcentrally with a sleeve 3 inwardly flanged at its rear end 4. A die holder S-has a rear portion 6 within the sleeve3just fitting within the flange 4 and is supported for free rotation on'the base by ball bearings 7 held betweenthe sleeve 3 and portion 6. At the front of the base is mounted a conventional soap box 8 through which the wire passes for lubricating purposes before entering the die; The die 9.1s secured within the front portion lfl of the die holder 5 which extends into the soap box 8 through anopening in thm a walln t e-fla e 1 It it -sma tes tha ith iel W 11 s ntr an se u e in the di holde t secure uniformity inthe drawn-wire. A ring121is secured to the forwardend of the tront portion m'of the d s b ld nsi the sn p bo a and tt old.e t sl i radially flanged at 13 between the walls 2 and 11. The purpose of these flanges is to protect the bearing7; from be n -rea h d by a so -hm .the bag a t baf in i p efe ably n eas by :PfllPMll be 14 on the fiangelawhich runs ina groove 15 in the wall 2. Th ts earanses, betw en th -par s r course exasssta s t d wi -fe sa e t e rer il tion. An; angular wall 16,;se eured to therear end of the se defines w thth Qa -wa et e basee transverse wall La rd-the sleeve 3 an annular chamber 17 forthecoolingfluid to counteract the vfrictional heat de eloped he d d rins dra ngandzc v y hr the'die holder-to the bearing. Coolinefluid is;ci rculated h quah th chamb r, .by in t and Outlet p pes 18 an 1. 1

e Other suitable forms of apparatus permitting rotation of: the drawing die may be 'lISCd. The invention may be practiced-in connection with bull blocks; rnoto blocks, both single and double deck; single block equipment; continuous drawing machines; and on the draw bench.

In dies for the drawing of conventional .wire of noncircular cross-sectiou the passage, in some cases, is of the desired cross-sectional shape throughout .itslength but,

.in other cases,.is of circular cross-sectional'shape over an initial portion, of its lengthfroru the entrytace of the I die and of the desired icross-sectional shape over a remainingsubstantial portion of its length, the first :shape merging into the second. Both forms may be-u-sed in a die according to the invention. lnidies for the drawing of conventional wire the passage may be made of. gradually diminishing cross-sectional area throughout the whole of its working length or throughout only a substantial .part thereof, being formed near the exit end with what is termed a bearing, i.e. a portion of uniform cross-sectional area along its length. in a die according to the present invention the passage may be formed in either of these ways, though the first is preferred.

Figures 2-5 illustrate a die according to the invention with a passage of which the general cross-sectional shape is square. In the die illustrated the square-cross-sectional shape of the passage is carried through its working length and the passage isof gradually diminishing cross-sectional area throughout this length. The-Wire presented to the die is diagrammatically shown at 26) in both Figure 3 and Figure 4. Referring to Figure 3, the-working length of the passage is the length between thepoint 21 where the wire to be drawn first comes into contact with the passage and the point 22 where the cross-sectional area oi the passage is at a minimum, the cross-section at the point 22 being that which determines the cross-section of the drawn wire and, being termed the effective cross-section of the passage. From the entry face 23 of the die to the point 22,. the cross-sectional area of the passage gradually diminishes as shown by the dotted lines 24 in Figure 3. the .passage'flares outwardly in the relief 25.

The essential difference between the die illustrated in Figures 2-5 and a die for the drawing of conventional wire of square cross-section is that the passage through the die illustrated, instead of being straight, is helically twisted about its longitudinal axis. This is best'illustrated in Figure 2 where the various squares indicate diagrammatically the area and orientation of various cross-sections of the passage from the entry face 23 to the point'22. The cross-section at the entryface is shown by the square 26, and that at the point 22'(n1r.rl-:- ing the end of the working length) by the square 33. These are the only two squares that would beseen as suc a lq kigs, t the die Theremnninasq re Beyond, the point 22 21 32 shown in lighter lines; -are included xtQiIldicate .the;gradual transition both ingarea and orientation .of .theeross-section, of the passage ,between the, ,entry face and the end of .the workingglength. The orientation of -t he .;square 27 diflers by ,1 5'.v clockwise from that .of: the square .26, and the orientation of each other squarecorjte pqnd nglydifiersfromthe precedingione, the orienta- ':'lIiQI1; of the square.33ithusedifiering by 105 {from .that of the square 26. The diifereuce between the :orientations of the squares :28 and v33, representingrespectively the beginning and end ofthe working lengthsof the passage, is 75"... Thus it ';W i11 be seen that the ,-passage illustrated ishelically twisted through 75 overits workinglen gth;;;thottgh-,this-,arnount of ,twistsis, it will be .realized,z.purelyillustrative. The area andz-orientation of the cross-section of the passage at'the beginning of its working lengthens! ,at-a point somewhat more than half way along-its working-length ;is further shown in the enoss-sections of the passage illustrated in Figures 4 and. 5 ,r espectively, the cross-sections in these -figures,"-it

will; be -1noted, beingjtaken looking towards ft-hetentry iacepf the idie. T heydie passage illustrated in Figures 2 to -5 is --ini;the form-10f a truncated twisted steep-sided py arnid. withta square ,base, the lines following the arners ofthe pyramidheing helical paths as can bet-seen v in figured; from a,consi dera tion, of for example, ithe .line;334 join-ing the corner 35 of the -square'26 ,to the corresponding corner -56, of the square .33 and following the -;c a rn ers. -,o f ;t-h e i-nterveningsquares. This, ;line;,also appears in part in Figure 3.

, Eigures 6 10 illustrate a formwf die according to the invention inwhichjthe-general cross-sectional shape of the Pas age, instead of being nomcircular',throughout the lengthgflffthe passage, ;iscircular over partof the working the dotted lines, 41-, and is helically twisted aboutits longiudina ax s- 7 in Figure .6 the orientation-and cross-sectional areaof thew-passage at the p0int138is shown by the four corners Aland that atthe point140 by the square 47. The increas-' ingly extendedicorners 43' and 44 indicate the gradual develcptnentof the square cross-section. and the accordpanying change-of orientation, and the squares 45 and 46 show the further. gradual change both in area and r nt until the pQintAfi-is reached. The'passage is helically twistedthrough between the point 38;,and

the point, 40.

The two dies described above are: illustrative of dies shown in Figures 2-5 but in which the general crosssectional shape of the passage, instead of being polygonal,

is oval (thisiterm being used herein to mean an area bounded. by any closed continuous curve of which one axis is substantially larger than the other at right angles tojit). The oval 48 showsv the cross-sectional areaand .erientat qm of. the entrance of. the passage, and theoval assures matically the gradual transition between these, the oval 50 indicating the area and orientation of the. beginning of the working length. The die passage illustrated in Figure '1 liis in the forrnof a truncated helically twisted cone of oval cross-section, the base beingthe oval 4 8 and the top' 7 the oval 55.

Wire is drawn-through apparatus of the invention in.

the same wayfas through ordinary drawing apparatus. The conditions which apply to the drawing of conventional wire or non-circular cross-section apply in'general' to the drawing of wire in accordance with the invention, but, in]addition it' is necessary, in' the practice ofthe 1nvent'io'n, to ensure that there is no excessive degree of re duction in each relative orientation of the ci-oss-sections cross-sectional shape and area which could be satisfactorily drawn through a die having a straight passage of a given cross-sectional shape and area, might not draw satisfactorily through a die according to the invention having a helically twisted passage of the same cross-- sectional shape and area because, although the degreeof reduction would not be excessive in one relative orientation of the wire and passage, it might be excessive in another relative orientation, so that in that orientation the wire could not be drawn down.

" In the drawing of wire according to the invention, somewhat more' careful attention should be given than that requiredin the drawing of conventional wire-to cleaning,

coatin'g'a'nd IubricantsJ The lubricant should be onehaving a high fat content and high melting point;- A most satisfactory lubricant has been found to be Standard In- 'dustrial Ghemicals No. 621.; Special care should be taken in' starting the drawing, proceeding gently at 'first and increasing speed very gradually. The wire should have a longtapered pointfree of slivers which advantageously ispulled snugly into the die and a second grip taken on itbefo re drawing starts. In the drawing, it has been founddesirable to have the wire travel ina straight line from a point'before it enters the die to the drawing block after it has passed through the die. v

h In the practice of the method of the invention, the die ordinarily rotates freely and without assistance by reason of the movement through" it of the wire to be drawn. However, it is clear that the greater is the maximum. helix angle'in' the passage (i.e. the maximum acute angle which any tangent to the helical curve of, for example,a corner cross-section.-

of a square passage forms with the longitudinallaxis 'of;

the passage) the greater is the tensile strain on'the wire as-it pa'sses through the passage. H to the invention has been successfully drawn through dies in which the maximum helix angle is somewhat inexcess of -30". The maximum helix angle which can be used without assisting the rotation of the die, will depend mainly upon the hardness of the wire, the degree of.

drawing, and the speed of drawing. If under any given conditions it is found that the strain on the wire with'a given helix angle in the passage is too great,,then it may be desirable to assist the rotation of the dieby some suitable form of rotary drive. The helix angle'will'begreat est at thewidest portion of the die passage and, as the lead-should of course be thesame throughout the length of the passage, will gradually diminish towards the effective cross-section of the passage as the passage becomes Steel wire according and the wire presented to it. I The diflerence is found to be greater the shorter is thelead-inthe passage. --With 'wire' of given nature drawn at a given-speed through 'a die with a helicallytwisted passage offa given lead, the resulting-drawn wire will'be of uniform lead throughout its length. The lead of the drawn wire mayrhowevenbe controllably' varied along-the'length offlthe wire, if that is in any case desirable, by. periodically somewhatrestraining therotation of the die or by periodically increasing thetension on'the drawn' wire leaving-the die. for example bypassing this wirebe'tween the die and the drawing block over arotating eccentric of which the rotation' periodically increases -the length "ofthe'jpath to be trayell'edby the wire jbetween the die and block. -Fig 'ure' l2' is a diagram illustrating the expressions finaxirnum radial diinensiori'-andr'ninim um-radialdimensionfl which have been defined and I referred to. above. The square represents thecross-section" of a wire or a passage. The circle61 is, as will be seen, the smallest circle centred on the longitudinal axis 62 which could be circumscribed about the square 60. The radius 63 of this circle is thus the maximum radial dimension of the square. The circle 64 is the largest circle centred on the longitudinal axis 62 which would be inscribed within the square '60. The radius 65 of this circle 64 is thus the radial dimension of the square 60. e

If:wire according to the invention of simple form is to be produced, the wire to be drawn is usually one having a general cross-sectional shape which is circular. If the radius of the wire to be drawn is greater than the maximum radial dimension of the effective cross-section of the die passage,.then the cross-sectional shape of the drawnvwire will be generally that of the effective crosssection of the passage. Figure .13 illustrates such a drawn steel wire where the die. passage was of square -It will be 'seen that the cross-sectional shape. of the 'wire is square throughout but that its ori- 'entation varies helically alongthe length of-the wire.

The faint dotted lines along the surface of the wire illus' tratediagrammatically the grain flow lines which run, as in conventional wire, in line with the longitudinal axis though; since they run up over the crests and down acrossgthe valleys of the drawn. wire, they are sinuous. These grain flow lines, it will be seen, are uninterrupted and lie Whollyin planes which includeythe longitudinal axis of the wire.

'It is often desirable to produce awire according to the invention of simple form of which the general crosssectional shape ispolygonal, but with rounded corners.

This can most conveniently be done by drawing Ithrough a die according to the invention, a round wire of which the radius isless than the maximum radial dimension of the the passage. GFigure 14 illustrates a.wire so produced with a die according tothe invention having a passage of square cross-sectional shape. Figure 15 shows on an enlarged scale the general cross-sectional shape of this wire, which, it will ,be noted,;is square with rounded corners. a

As in the drawing of conventional w' e, it is often necessary to effect two or more draws to reach a given cross-sectional shape for wire according to the inven- 'tion. If this wire is to be of simple form, it has been found that the lead of the helix of the passage in the second and each subsequent die must be at least substantially the same as the lead of the helixed wire presented to it.

Figure 16 illustrates an example of wire made accordmg to the invention of complex form. This wire is produced by drawing, through a die such as shown in Figures 2-5 a conventional wire of square cross-section, aside of the cross-section of the wire being shorter than the diagonal of the, effective cross-section of the passage. It will be noted that at some points along its length, e.g. at theend of the piece shown in Figure 16,1the wire is of square cross-section, whereas atother points, e-.g. that at which the CI'OSSrSBCtiQH shown in Figure 17 is taken, the

Wi e th si ns tum. .o .nnesbape and area alte a re ar wi h that the .othe sh pe and area, the rgs sss i l a ea. varyin .repea edly.a dmes alon t length -th Wi e. between a .ntaximum ..Q -1* i u 1. and:ami imitm.(E sg qfl)- through a die' such as shown in Figures 2-5 in which the passage is helically twisted in a left hand direction. As appears from the view of the end of the wire in Figure 18 and the cross-sectional view in Figure 19, the cross sectional shape and area of the wire vary along its length from square and maximum to octagonal and minimum as in the case of the wire of Figure 16. However the alternation of shapes and areas is more frequent in the wire of Figure 18.

The further example of a wire of complex form made according to the invention illustrated in Figures 20 and 21 is produced by drawing a wire of simple form such as shown in Figure 13 through a conventional die with a straight passage of square cross-section.

For the sake of simplicity the examples of wire accord ing to the invention of complex form have all been illustrated on the basis of wire of square cross-section drawn through passages of square cross-section. However, the cross-sectional shape of the wire to be drawn may differ from that of the passage through which it is drawn and, in a case like that described with reference to Figure 18, the lead of the wire may difier from that of the die passage. An extremely wide variety of wires of complex form according to the invention may thus be produced.

In certain cases in the production of wire according to the invention of complex form, some torsional forces in the wire to be drawn may be developed owing to the greater resistance presented to its passage through the die in certain relative orientations of the cross-sectional shapes of the Wire and the entrance to the die passage than in other such orientations. In such cases it may be desirable to restrain the wire to be drawn from any tendency to turn about its axis as it approaches the die.

The wire made according to the invention enables the production of a variety of articles of improved characteristics and/or capable of being manufactured at substantial economies. Thus, threaded nails made from wire according to the invention of simple form have all the desirable characteristics of presently available threaded nails and can be produced at far less cost-in fact at a cost not appreciably exceeding that of ordinary nails. Threaded nails according to the invention may be made from wire produced by drawing through a die according to the invention, having a passage of square cross-section, a round wire of which the cross-sectional diameter is shorter than the length of a diagonal of the effective cross-section of the passage.

Ordinary barbed wire consists of two strands of line wire twisted together with the barbs held between them, the use of two strands of line wire being, necessary to hold the barbs at the desired spacing along the length of the wire. According to the invention barbed wire may be made with a single line wire and barbs composed of wire according to the invention of simple form, preferably with a general cross-sectional shape which is polygonal with sharp corners. Normally the cross-sectional shape will be square or triangular. wrapped around the line wire in the usual way, resist displacement along it by reason of the engagement of their corners with its surface. Alternatively, the converse arrangement of a single helixed line wire of simple form and barbs of conventional wire may be used. In

Such barbs, when reinforcement is ,ordinarily,.made..of,conventionalgtrolled or drawn rods.- The rolled rods .can;-,be.,produgedgwith patterned surfaces which increase,;the,bonding iof;the concrete to them in thefinal structure, and consequently permit of ahigher design'edload forlthe structure. Drawn rods have an appreciably-greatertensile strength than those that are'rolled, and'building specifications consequently allow a substantial increas'tn designed load where the reinforcement consists of drawn rods than when it consists of those that are rolled. According to the invention concrete reinforcing rods may be produced having advantages unobtainable in any such rods pre- .viously available. Concrete reinforcing rods according to I the invention are drawn with different cross-sectional areas and shapes along their length. Preferably, the rods are formed as described in connection with Figure 18, the lead of one helix. being desirably different from that of the other. They thus have the tensile strength of conventional drawn rods together with the advantages of increased bonding provided by the patterned rolled rods referred to above. With rods according to the invention, substantially higher designed loads in reinforced concrete structures are possible than with any rods previously available. This advantage is particularly significant for pre-stressed concrete construction where bonding of the steel reinforcement to the concrete is of special importance.

Non-skid gratings are used for a variety of purposes, for example, as the treads and landings of steel stairways and ladders, the non-skid feature being particularly im-' portant in circumstances where oil or grease is present, for example, in ships engine rooms. One form of nonskid gratings at present widely used is one having bars of rectangular section running in one direction and helically twisted rods on top of'these bars in a direction at right angles to them. The rods are forged down into the upper surface of the bars, this forging down being necessary to bring the upper surface of the bars into substantially the same plane as the upper surface of the rods, so that the bars act to arrest slippage in the direction of the helix angle of the rods. According to the invention a non-skid grating of entirely satisfactory characteristics is produced at a greatsaving of cost by forming the sectional shapes at different points along the length of the rods. A satisfactory non-skid grating may be composed of such rods running in one direction only, the presence of rods or bars running in a direction at right angles being unnecessary for prevention of skidding because the rods referred to, being of complex rather than simple form, themselves ofl'er resistance to skidding in all directions.

This application is a continuation-in-part of an earlier application Serial No. 383,625 filed October 1, 1953, now abandoned.

What we claim as our invention is:

1. A wire drawing die having a passage therethrough of gradually diminishing cross-sectional area throughout a substantial part of its working length, said passage having a general cross-sectional shape which is non-circular over at least a substantial portion of its working length and being helically twisted about its longitudinal axis throughout said portion of non-circular cross-sectional shape, whereby a wire drawn by said die is characterized by crests and valleys wherein grain flow. lines run longitudinally across the valleys in thedirection 11 over at least a substantial portion of its working length and being helically'twisted about its longitudinal axis throughout said portion of" polygonal cross-sectional shape, whereby a wire drawn by said die is characterized by crests and valleys wherein grain flow lines run longitudinally across the valleys in the direction of the longitudinal axis of the wire. t t a 7 References Cited in the file of this patent UNITED STATES PATENTS 12 Poulson June 11, 1889 McMurray Dec. 3, 1889 Ballou Jan.18, 1910 Jones June 15, 1920 Davies Oct. 25, 1921 Howartb .L May 30, 1922 BaTton Nov. 3, 1925 Hjelm Oct. 31, 19 33 Drapeau May 13, 1941 Hawkinson June 17, 1952 Graham I. June 24,1952