TM9-2815-202-34 (19)    Determine  quantity  of  diffuser  shims (33) as follows: (a) (b) (c) (d) (e) (f) (9) (h) Place  center  housing  assembly (12)  upright  with  turbine  wheel resting on flat surface. Place flat bar (53) across diffuser vanes (54). Measure distance from top of bar (53) to face of thrust collar (38) with depth gage (55). Measure distance from top of bar (53) to face of diffuser vanes (54). Subtract  two  readings.  Difference is height of diffuser vanes above face of thrust collar. Rotate bar (53) 180 degrees and repeat  measurements.  Results should agree within 0.001 inch. Place impeller (32), blades up, on flat  surface  and  measure  height of  impeller  blades  from  flat surface. Measure at least 1/8 inch back from blade tip edge. Rotate  impeller  180  degrees  and repeat  measurement.  Results should agree within 0.001 inch. NOTE Diffuser  shims  come  in  0.005,0.010, and  0.020  inch  thicknesses. (i) Subtract impeller blade tip height from  diffuser  vane  height.  Answer is  height  difference  diffuser  is higher  than  impeller  blade  tips. Add or remove shims (33), as directed in step (18), to attain a height difference of 0.013 to 0.017  inch. Wear   heat-resistant   gloves when  handling  heated  parts. Metal  components  will dissipate  heat  quickly.  Burns to  personnel  will  result. 6-51