TM-9-2815-200-35 Maintenance Manual for AVDS-1790-2M AVDS-1790-2A and AVDS-1790-2AM Engines Download
Page 473 of 779
Figure 6-214. Improvised camshaft trueing device. (a) Checking camshaft bearing journal run-out. Camshafts may be straightened if the runout of any one camshaft bearing surface (journal), when using a dial indicator, does not exceed 0.060 inch total indicator reading (TIR) when supported at the two adjacent bearing journals. Camshafts that exceed 0.060 inch runout between any two journals must be discarded. Maximum journal runout of straightened camshafts is 0.002 inch (TIR) when supported at the two adjacent journals. After straightening a camshaft, the maximum acceptable runout of the center bearing journal, when supported at the end journals, is 0.015 inch (TIR). Check camshaft bearing journal runout as follows: (1) Support the camshaft at the two end journals in “V” blocks on a surface plate or other available centering device, such as a machine lathe. (2) Position a dial indicator at the center bearing journal and obtain a zero reading on the dial. (3) Rotate the camshaft and determine the maximum travel of the dial indicator needle. If travel (TIR) exceeds 0.015 inch the camshaft must be straightened. (4) Repeat steps (2) and (3), above for each bearing journal and mark position and dimension of maximum dial indicator reading at (5) Check runout of each camshaft bearing journal. Support the camshaft in “V” blocks at the adjacent journals, and using a dial indicator, check and record journal runout (TIR) dimensions. If runout exceeds 0.002 inch, cam shaft must be straightened. (b) Straightening camshaft. (1) Install camshaft on trueing device with bearing journal having the maximum runout (TIR) positioned under the pressing spindle. (The camshaft journals must be resting on the support blocks when rotating the cam- shaft to determine the runout.) Set dial on in- dicator to “zero” and rotate camshaft to determine location of runout (TIR) and record reading. (2) Turn camshaft until bearing journal marked to indicate the maximum runout (high side) is adjacent to the spindle (do not press on journals). Apply spindle pressure on the camshaft until dial indicator reads ap- proximately one half of the TIR reading recorded in (a), above. Release pressure on cam shaft and recheck runout by turning camshaft several revolutions. Note. Pressing force required to straighten cam shaft is a matter of judgement. It may be necessary to turn camshaft and apply pressing force several times in order to acquire the technique necessary to true the bearing journal. (3) Apply pressure as required until the journal is within the 0.002 maximum TIR. (4) Reposition camshaft on supports and true other bearing journals is a similar manner. (5) After trueing all bearing journals, recheck camshaft as outlined in procedure (a), above. If readings do not meet dimensions specified, repeat trueing operation. (c) Inspection of camshaft after straightening. (1) Magnaflux each camshaft and inspect for cracks. Observe transition areas at bearing surfaces and at cam lobe bases. Cam- shafts with evidence of cracks must be discarded. (2) Inspect for damage to bearing journals. Minor nicks and scratches can be removed using crocus cloth. (3) Check bearing journals for out-of- round to be certain area was not flattened during trueing. Maximum acceptable out-of-round is 0.002 inch (TIR). Replace camshaft if this tolerance is exceeded. 6-179