A method of manufacture of a power assisted steering control valve; said control valve including a pinion shaft, an input shaft and a torsion bar; method including the steps of: a. receiving into clamping fixtures of an assembly machine a pre-assembly of said pinion shaft, said input shaft and said torsion bar, with said torsion bar inserted into input shaft as a free sliding fit with a splined first end projecting from an outer end of input shaft, and a pinion end of input shaft and second end of torsion bar loosely located in socket and central bore of the pinion shaft, b. driving said input shaft and inserted torsion bar axially towards said pinion shaft to bring a locating shoulder of said input shaft into contact with an end of said pinion shaft and recording a reading of a linear encoder at this point, c. using said reading of said encoder to calculate record a predefined axial clearance for rotation between an end of said pinion shaft and said locating shoulder of said input shaft, d. rotating said input shaft in opposing directions between rotation limiting stops (48, 50) so as to establish a midpoint of rotation of said input shaft relative to said pinion shaft, (e) axially withdrawing said input shaft and said torsion bar from said pinion shaft to open a predetermined gap between said locating shoulder of said input shaft and said end of said pinion haft, f. moving support collets into position in said gap to provide support for said locating shoulder against said end of said pinion shaft, g. pressing a first end of said torsion bar into said input shaft to form a locked together assembly of said input shaft and said torsion bar, h. withdrawing said support collets and axially advancing said assembly of said input shaft and said torsion bar into said pinion shaft until said linear encoder reads said predefined axial clearance for rotation so as to press a second end of said torsion bar into a locked together assembly (32, 34) with said pinion shaft. a. receiving into clamping fixtures of an assembly machine a pre-assembly of said pinion shaft, said input shaft and said torsion bar, with said torsion bar inserted into input shaft as a free sliding fit with a splined first end projecting from an outer end of input shaft, and a pinion end of input shaft and second end of torsion bar loosely located in socket and central bore of the pinion shaft, b. driving said input shaft and inserted torsion bar axially towards said pinion shaft to bring a locating shoulder of said input shaft into contact with an end of said pinion shaft and recording a reading of a linear encoder at this point, c. using said reading of said encoder to calculate record a predefined axial clearance for rotation between an end of said pinion shaft and said locating shoulder of said input shaft, d. rotating said input shaft in opposing directions between rotation limiting stops (48, 50) so as to establish a midpoint of rotation of said input shaft relative to said pinion shaft, (e) axially withdrawing said input shaft and said torsion bar from said pinion shaft to open a predetermined gap between said locating shoulder of said input shaft and said end of said pinion haft, f. moving support collets into position in said gap to provide support for said locating shoulder against said end of said pinion shaft, g. pressing a first end of said torsion bar into said input shaft to form a locked together assembly of said input shaft and said torsion bar, h. withdrawing said support collets and axially advancing said assembly of said input shaft and said torsion bar into said pinion shaft until said linear encoder reads said predefined axial clearance for rotation so as to press a second end of said torsion bar into a locked together assembly (32, 34) with said pinion shaft.