Method for producing a propeller shaft

DETAILED DESCRIPTION It is a first object of the invention to provide a propeller shaft which is able to be produced with fewer working steps for a shorter period of time and hence which is inexpensive to manufacture, higher in accuracy, lighter in weight and hence economically advantageous and superior in balance of strength.
It is another object of the invention to provide a method for producing such a favorable propeller shaft mentioned in the above first object of the invention.
It is a further object of the invention to provide a method for forming a phase indexing reference of spline shafts whose irregular portion is easily formed and there is no risk of the irregular portion falling off.
In order to accomplish the above objects, in the propeller shaft according to the invention, at least one of said male and female shafts is wholly made of a hollow tube, and its yoke is an integral part of said hollow tube which has been worked to form it and its spline sliding portion is another integral part of said hollow tube which has been plastically worked to form it.
The yoke may be formed as a separate part and press-fitted into one end of the hollow tube and welded thereat.
In a preferred embodiment of the invention, the spline sliding portion of each of the male and female shafts has spline teeth whose number is an integer within the range of numerals obtained by multiplying the numeral indicating a larger spline diameter D in mm by 0.
12 to 0.
25.
Moreover, the spline teeth have a spline tooth root angle within the range of 90 to 120 degrees enclosed between side faces of adjacent spline teeth.
In another aspect of the invention, the method for producing a propeller shaft according to the invention comprises a plastic working pretreatment step for making a hollow tube for said male or female shaft into a predetermined length and pretreating it; a spline sliding portion plastic working step for forming a spline sliding portion at said one end with a press-die; and a yoke providing step for providing a yoke on said other end of said hollow tube opposite to said spline sliding portion, any one of said last mentioned two steps being carried out prior to the other