before proceeding to further describe the invention , i would like to explain how i distinguish the various flex patterns for shafts . the terms for shaft flex usually used in the industry , extra stiff ( x ), stiff ( s ), regular ( r ) and ladies ( l ), are relative terms for a particular shaft type and do not have an absolute definition agreed upon to cover all types of shaft . therefore let me explain that for this invention i have been measuring shaft flex with the test shown diagramatically in fig1 . in fig1 a shaft has been horizontally clamped at its grip end and loaded with a 6 lb . 41 / 4 oz . weight hung 5 / 8 inch from its hosel end . previously the unloaded horizontal cantilever position of the shaft was determined to define a &# 34 ; 0 &# 34 ; line from which the loaded shaft deflection can now be measured ( in millimeters ) at three specified horizontal distances ( a , b , c ) from the shaft &# 39 ; s grip end . the three specified horizontal distances are : thus , by means of the test of fig1 any shaft can be said to have characteristic deflection readings which then can be correlated with golfers &# 39 ; reactions to the shaft as being of extra stiff , stiff , regular , or ladies flex . in designing my new shaft i started with a very popular standard weight shaft , propel ii ™, whose deflection characteristics were known to be acceptably labeled as follows : ______________________________________ deflection ( mm )± 5mmflex shaft length a b c______________________________________s 44 &# 34 ; 13 62 140r 44 &# 34 ; 14 65 150l 44 &# 34 ; 15 72 167______________________________________ i then experimented with the parameters of my new shaft , particularly the taper applied to the shaft from handle to hosel end , so as to closely approximate the familiar propel ii ™ deflection pattern . this resulted in the following measured deflection readings for the ucv - 304 ™. table ii______________________________________ deflection ( mm )± 5mmflex shaft length a b c______________________________________x 45 &# 34 ; 13 57 127s 44 &# 34 ; 14 60 134r 44 &# 34 ; 15 65 146l 44 &# 34 ; 17 74 166______________________________________ in practice i have found that the above deflection readings for the ucv - 304 ™ are meaningful to golfers in that the flex labels x , s , r and l applied to shafts give a good indication of how the shaft will play in terms of stiffness when compared with well known previously existing shafts , such as propel ii ™. however , because the ucv - 304 ™ is made with unusually thin wall construction ( because of its low weight ), i had to modify the shaft taper considerably to achieve flex characteristics comparable to standard weight shafts like the propel ii ™. fig1 shows outside shaft diameter ( plotted vertically ) versus distance along a 45 &# 34 ; shaft ( plotted horizontally ) for a propel ii ™ r flex wood shaft ( envelope only ) and for my ucv - 304 r flex wood shaft ( both the actual step pattern and the envelope ). note that while some shafts are manufactured to taper smoothly from handle end to hosel end , it is more common for shafts to be tapered in quantized &# 34 ; steps ,&# 34 ; resulting in a characteristic &# 34 ; step pattern &# 34 ; for each type of shaft . in practice , the actual &# 34 ; steps &# 34 ; of a step pattern can be used to identify a particular shaft model and ( if chosen carefully ) enhance its appearance , while the &# 34 ; envelope &# 34 ; of the step pattern characterizes the major physical effect of the step pattern on the shaft flex and other play characteristics of the shaft . thus in making the comparison of fig1 only the relatively smooth envelope of the propel ii ™ r flex step pattern is shown compared with the envelope and actual step pattern of my ucv - 304 ™ shaft . it can readily be seen that the envelopes of the two step patterns diverge considerably because my step pattern begins its taper about 9 &# 34 ; further towards the hosel end of the shaft and then proceeds at a much faster taper than the standard weight propel ii ™ ( i . e . the outside diameter ( o . d .) of my ucv - 304 ™ shaft tapers from 0 . 600 to 0 . 340 inches along just 22 inches of shaft length , compared to about 31 inches of shaft length used for an approximately comparable decrease in the outside diameter of the propel ii ™ shaft ). similarly , fig1 shows outside shaft diameter ( plotted vertically ) versus distance along a 39 &# 34 ; shaft ( plotted horizontally ) for the outer envelope of a propel ii ™ r flex iron shaft and the actual step pattern and outer envelope of the pattern for my ucv - 304 ™ r flex iron shaft . in this case the envelopes of the two step patterns also diverge considerably because my ucv - 304 step pattern begins its taper about 51 / 2 inches further toward the hosel end of the shaft than the propel ii and then proceeds at a much faster taper than the regular weight club . thus in fig1 and 12 the envelope of my novel step pattern gives the solution which i found by experimentation and trial and error to make a 3 . 4 oz . shaft have a flex pattern characteristic similar to that of a 4 . 4 oz . regular weight shaft . of course , in both cases the envelope is only an imaginary line connecting the actual step pattern of my club . however , it is the envelope of the steps which gives the shaft its characteristic flex pattern if the actual individual steps are relatively shallow and close together as is the case with my step pattern ; in such a case , a variety of step patterns having the same envelope will tend to cause the same pattern of shaft flex , even though the individual step patterns may differ quite noticeably . therefore , whenever in this specification i give a particular step pattern as the solution to the problem of obtaining a desired flex in a given shaft , it is to be understood my solution includes all equivalent patterns ; that is , all step patterns having substantially the same envelope . however , the particular step pattern for my shaft shown in fig1 and 12 ( and repeated with some variation throughout fig1 - 7 ) does have some special characteristics in addition to its carefully selected envelope . this can most easily be seen in fig6 and 2 which illustrate step patterned shafts following the designs of fig1 and 12 respectively . it is immediately apparent from fig6 and 2 that my step pattern is able to fit within the desired envelope while producing a regular , pleasing appearance on the shaft . my steps have a minimum depth of about 0 . 010 inch to assure that they will be easily visible on the finished shaft and rarely exceed 0 . 020 in depth . the steps fall quite naturally into three sizes distinguished by their length along the shaft : i consistently repeat the small and medium steps in the subpattern &# 34 ; medium - small - small - medium &# 34 ; and the large steps in the subpattern &# 34 ; large - large .&# 34 ; joined together these two subpatterns appear as &# 34 ; medium - small - small - medium - large - large &# 34 ; a cycle that appears twice or more on each shaft ( depending on the shaft length ) to give each shaft both a distinctive appearance and the envelope required for the designed flex pattern . for example , see fig1 where starting from the left ( grip ) end of the shaft the lengths of the steps are : medium ( 0 . 75 inch ), small ( 0 . 50 inch ), small , medium , large ( 1 . 75 inch ), large . turning now to the problem of fabricating clubs of the above design , to meet all the various objectives of my invention i had to discover : ( a ) criteria for selecting metals for my shaft tubes that would not become permanently bent in play or brittle enough to break in play ( b ) test criteria for the finished light weight shafts that would permit me to reject shafts that were defective and might bend or break in play ( c ) how big to make each starting work piece so that i could give it the desired step pattern , size and weight , taking into account that tapering a shaft tube will increase its length , while trimming the ends of the shaft to achieve the finished length ( after tapering ) will reduce its weight ( d ) how to modify my answers to ( a ), ( b ) and ( c ) above to produce shafts suitable for once again i proceeded by experimentation and trial and error to solve these fabrication problems . the results of my efforts are summarized in fig1 - 8 , each of which is a bill of material for fabricating a particular shaft , usually in a range of lengths . fig1 for example , is the bill of material for an s flex shaft designed for iron heads , the finished shaft length varying in 1 / 2 inch steps from 391 / 2 inches to 35 inches . while fig1 specifies that the shaft is to be made of aisi 6150 alloy steel seamless tubing , in fact welded tubing may be used . the advantage of seamless tubing is merely that if you are willing to pay its premium price , forming and welding of flat strip stock into tubing ( and the problems of getting a good weld ) can be avoided altogether . similarly , while i have found that aisi 6150 alloy steel is very satisfactory for fabricating my shafts , the general criteria for the metal of my shafts is that in spite of the thin walls of my shafts the metal must not cause the shaft to become permanently bent or break due to brittleness when used by the average golfer . in practice i have found that these criteria can be met by metals that have , after heat treatment , a yield strength equal to or greater than 220 , 000 lbs ./ in . 2 and an ultimate strength equal to or greater than 240 , 000 lbs ./ in . 2 aisi 6150 alloy steel is such a metal , and other examples are aisi 4150 , 4340 , 5150 , 8650 alloy steels . returning now to fig1 the initial size of each workpiece is specified so that after step forming , hosel swaging , and cutting to finished length , the shaft will have both the desired dimensions and the desired weight . in the fig . &# 34 ; o . a . l .&# 34 ; is the overall length of the shaft , &# 34 ; ref .&# 34 ; is a reference distance from an indicated shaft end , and &# 34 ; a &# 34 ; labels the portion of the shaft length remaining at the hosel end below the step of smallest outside diameter . my initial tube sizes and weights have been selected so that after the steps have been formed and the hosel swaged , about 1 / 2 inch can be trimmed from the grip end of the shaft and about 1 inch from the hosel end ; thus , irregularities introduced at the tube ends during manufacture are trimmed away . another feature of my invention which appears in my s and r flex shafts for clubs with iron heads is that the initial workpiece is specified to have a slightly thicker wall so that the final shaft will have a slightly thicker hosel to improve its performance on the permanent set test ( this permanent set test will be described below ). as can be seen at the top of fig1 and 2 , the length of the thicker portion of the workpiece is designated by the initials &# 34 ; h . l .&# 34 ;, while the thinner main portion of the workpiece is designated &# 34 ; g . l .&# 34 ;. while the basic operations for forming and finishing my ucv - 304 ™ tube ( given the specified bill of materials ) generally follow the procedure for making a standard weight tube , those practicing my invention will probably find it necessary to make the following additions and adjustments to operations originally designed for tubes of standard weight because of the tube &# 39 ; s thin wall and the higher strength of the material used : ( a ) additional steps for weighing and measuring the initial workpiece and final shaft should be introduced to assure that the tube stays within the specified tolerances ( b ) to reduce any hardness introduced while forming the workpiece , an additional annealing step may be added just before the shaft steps are formed , the additional annealing step consisting of heating the workpiece to 1250 ° f . and slowly cooling it to ambient temperature ( c ) the steps for hosel swaging and shaft straightening may be performed at speeds slower than those used for standard weight tubes ( d ) stress relief steps may be introduced both before and after plating the shafts , the stress relief consisting of placing the shafts in an oven for one hour at 450 ° f . ( e ) additional hand alignment of the shaft before final stress relief steps may be added when the metal used is a carbon alloy steel , such as 6150 alloy steel , the initial workpiece should preferably have a sphereodized fine structure and the austemper type heat treatment of the shaft ( after forming the steps and swaging the hosel end ) should produce a banite structure in the final shaft . there are two tests that i perform on my completed shafts to assure that they will be suitably resilient and durable when used by average golfers . in fig1 - 7 permanent set criteria ( w , s ) are given for each shaft . fig8 and 9 are a side and end view of the permanent set test i use to check that the criteria have been met . briefly , the test apparatus consists of an adjustable clamp for clamping the hosel end of the shaft ( protected by a matching steel bushing of length b inches having a club head hosel - simulating bore ) at 12 ° from the horizontal . then a specified weight of w lbs . is applied for 60 seconds to the grip end of the shaft and the permanent deflection the shaft experiences is measured in inches . in my shafts this permanent set deflection of s inches must preferably not exceed 0 . 100 inches to assure that normal use will not put a noticeable permanent bend in the shaft . in greater detail , the permanent set test is performed as follows : 1 . the appropriate matching hosel bushing of length b inches is inserted into the set test fixture and locked into place so that the lower edge of the bushing is flush with the set test fixture . 2 . the shaft is inserted into the hosel bushing , in the fixture , and twisted to assure proper alignment with the dial indicator stem and to insure a tight fit in the bushing . 3 . the dial indicator is then brought down , on its support rods , and the indicator stem depressed against the stem , locked into position with a reading of 0 . 600 &# 34 ; on the revolution counter . the bezel is then rotated to bring the indicator pointer to zero . 4 . the specified test load weight of w lbs . is then applied by means of the standard weight hook at a point 20 &# 34 ; from the test bushing and slowly lowered by hand and then released . 5 . at the end of 60 seconds , the test load is removed and the shaft moved up slowly -- guided by hand -- again contacting the indicator stem until upward movement of the shaft stops . 6 . the indicator is then read in increments of 0 . 001 &# 34 ; with the difference between the initial 0 . 600 &# 34 ; reading and the present reading being the amount of permanent set s in inches . the second test that i apply to my finished shafts is the modified izod impact test shown diagramatically from the side in fig1 . briefly , 5 inch lengths cut from various portions of my shaft are clamped vertically to project a distance a of 13 / 4 inches above a vice and subjected to a horizontal blow by a weighted , swinging pendulum steel edge w at a point a about 3 / 4 inches from its end . the starting potential energy of the pendulum w is known and always chosen to exceed that necessary to break the shaft . in overcoming the shaft &# 39 ; s resistance to breakage , the pendulum loses kinetic energy and this loss of energy can be read by means associated with the test equipment but not shown in fig1 to give the shaft &# 39 ; s resistance to impact in ft .- lbs . in practice i perform my impact tests on an olsen universal impact testing machine manufactured by tinius olsen testing machine company of philadelphia , pa . empirically i have discovered that tubes of my design should preferably have an impact resistance of at least 10 ft .- lbs . so that they are certain to stand up in normal use . while so far in this description i have mostly relied on fig1 to describe my new lightweight shaft and its method of manufacture what i have said about fig1 applies mutatis mutandis to the shaft designs of fig2 - 7 so my shaft can be manufactured in a great variety of lengths and flexes . it should be noted that while i have referred to my shaft as being of about 3 . 4 oz . in weight , in fact by using slightly modified designs i have been able to produce shafts of my design as light as 2 . 9 oz ., but these shafts performed so poorly on the impact test that i felt that they were not rugged enough to sell to golfers generally , though they played well enough to satisfy golfers who would treat them with special care . thus , my choice of a 3 . 4 oz . club was made so that the advantages of the club would be available to average golfers without concern for shaft breakage under extreme conditions ( such as where the golfer accidently abuses the shaft ). although in describing the embodiments shown in fig1 - 7 i have been very specific in citing details to aid those skilled in the art in replicating my shaft and have called attention only to some of the most prominent advantages and characteristics , my invention includes other embodiments reasonably equivalent within the spirit of the invention and has other advantages that will be readily apparent to those skilled in the art when reading this specification .
a light weight golf club shaft and a method of making it out of metal tubing are described . the metal must have , after heat treatment , a yield strength equal to or greater than 220 , 000 lbs ./ in . 2 to avoid permanent shaft deflection in use . the metal must also have an ultimate strength equal to or greater than 240 , 000 lbs ./ in . 2 to avoid shaft breakage in use . the finished shaft must attain the impact and permanent set results set forth in the specification . to fabricate the shaft in a variety of lengths and flex patterns needed to accommodate a golfer &# 39 ; s individual needs , a collection of manufacturing specifications incorporating relationships between the working material , the initial size of the work piece , and the final shaft product length , taper , weight , and flex are presented . a test is defined for measuring the final shaft product &# 39 ; s flex pattern .