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inch. Out-of-round should not exceed .0005 inch. The 7-31. Connecting Rods (Dimensional Inspection). Discard ST-73 gage is specially made so that it can be set with a all connecting rod bolts and nuts; new bolts and nuts are micrometer. If the diameter of any bushing is oversize, or to be used on assembly. Check condition of bore in large excessively out-of-round all the bushing in the end for seating of the bearing inserts. Check bore in small counterweight must be replaced.
7-35. Crankshaft Counterweight Bushing. Wear or damage to the crankshaft counterweight bushing (21), figure 7-3 located in the crankshaft counterweight lobes is almost impossible to detect by normal inspection pro-cedures. Because of this situation and as damage to the counterweight bushing could cause failure to the counterweight and/or the crankshaft, it is mandatory that these bushings be replaced at overhaul. The procedure for
the removal and replacement of the crankshaft counterweight bushing is contained in paragraph 7-43.
REPAIR AND REPLACEMENT

7-36. Repair all crankcase, crankshaft and reciprocating parts in accordance with the general instructions contain-ed in Section 3. Specific instructions follow.
7-37 Crankshaft (Bearing Surfaces). During overhaul of the crankshaft, the operator must determine if it has stan-dard or undersize bearing journals, then proceed with its overhaul accordingly. Undersize crankshafts are iden-tified by a code symbol stamped on the front of the flange as a suffix to the part number. In addition to the code
1.
Tapered Sleeve (Crankpin End) 5.Gage Arm symbols the letters RN are stamped as a suffix to the

2.
Tapered Sleeve (Piston Pin End) 6. Adjusting Screw serial number indicating the shaft has been renitrided.

3.
Arbor  (Crankpin Sleeve) 7. Wing Nut The code symbols are, M03MP (main and crankpin jour-

4.
Arbor  (Piston Pin Sleeve) nals 0.003 inch undersize), M03M (main bearing journals

0.003 inch undersize), M03P (crankpin bearing journals
Figure  7-5. Checking Parallelism of 0.003 inch undersize). If the maximum service limits are Connecting Rods exceeded (reference 501 or 502, Table of Limits) standard
7-5

Section 7 LYCOMING
Crankcase.Crankshaft OVERHAUL MANUAL and Reciprocating Parts shafts may be polished to 0.003 inch undersize and fitted with 0.003 inch undersize bearing inserts. Renitrided
0.003 inch undersize shafts may be polished to 0.006 inch undersize and fitted with 0.006 inch undersize bearing in- serts. Do not allow lathe speed to exceed 150 RPM at any time during polishing operation.
NOTE

Note that if one surface is polished to .003 or .006 under size all corresponding surfaces must be polished to same size. Polishing to undersize is preferred to grinding because shafts that are polished do not require renitriding whereas any grinding operation requires that the shaft be renitrided This is necessary because of the nonuniformity of grinding tools. The possibility exists wherein the grin- ding wheel will cut through the nitrided surfaces on one or more of the journal radii causing area of stress concentra-tion that can develop into fatigue cracks and ultimately result in a broken crankshaft.
　
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