Aft Head Nozzle

When we were asked to make this part we had some significant manufacturing problems to overcome.  The part came to us as a 13" OD, 85 pound forging made of 4340 alloy steel.  The part required us to hold the wall thickness between the ID and OD spherical radius to with .005" while blending in a straight OD & ID. 

    The first challenge that we had to figure was how to machine the two concentric spherical radii.  Bob (Grindley's founder) designed and built a hydraulically driven tilting mandrel for an engine lathe.  It had two single action hydraulic cylinders driven by tubes through the spindle and attached to a rotary coupling.

    First we held the part on the flange and roughed the face and OD and also turned the OD groove.  In the same setup we roughed the ID radius.  Using the tilting fixture, the OD profile was roughed first.  After roughing, the part was heat treated and it would distort about .030".  Bob then came up with fixtures that forced the part into shape and we drew the parts at draw temperature and they held their modified shape.

    Then came the finishing of the part.   The part was held on the flange in a chuck and using the tracer generated the ID profile, including a counterbore.  It was then mounted on the tilting fixture.   The fixture had been turned with a radius so that it would closely fit the ID radius profile and was held fast by clamping the OD groove to the mandrel.  The turning began with the nose section running true for turning, boring and threading.   As the tool passed through the fillet radius, the part slowly began to tilt as the tool moved up the spherical radius.  At the finish of the operation the OD and face ran true while the nose was running wildly eccentric.  That was fun!!  This part was manufactured in the mid 1960's.  We were using the newest commercially available equipment of the period.