TM 1-1520-238-23
6-9
6.1.
DRIVE SHAFT INSPECTION – continued
d. Check shaft tubes for dents.
(1) Dents are considered “negative” material displacement, material moved below surrounding surface. Use
depth gage for dent check on straight surfaces.
(2) Sharp dents are not acceptable.
(a) Sharp dents are defined as those depressions that initiate or terminate in a discernible discontinuity or
interruption in smooth flow of metal.
(b) Sharp dents are considered to be 0.250 INCH or less deep.
(c) A sharp dent can be detected by tracing a nonmetallic pointed instrument across surface of tube and
noting abrupt change in direction of instrument tip.
(3) Non-sharp dents are acceptable, provided they meet following dimensional criteria.
(a) The width dimensions signify shortest distance across dent.
(b) The length dimensions signify longest distance across dent.
DENT WIDTH
DENT LENGTH
DENT DEPTH
DISPOSITION
Less than 0.250 INCH
Not Applicable
Not Applicable
Reject Tube
0.250 - 0.375 INCH
2.0 INCH Maximum
0.024 INCH Maximum
Accept Tube
0.375 - 0.500 INCH
2.5 INCH Maximum
0.036 INCH Maximum
Accept Tube
0.500- 0.875 INCH
3.0 INCH Maximum
0.048 INCH Maximum
Accept Tube
More than 0.875 INCH
Not Applicable
Not Applicable
Reject Tube
(4) Drive shaft tubes may show circumferential lines indicating a slight change in cylindrical surface (a smooth
step).
(a) These lines have been referred to as “ripples”. Ripples are a result of manufacturing process.
1 Ripples are considered a “positive” material displacement condition, material raised above sur-
rounding surface.
2 Ripples are acceptable, provided they do not exceed 0.024 INCHES in step height or 7.50 INCH
in circumferential arc length (190 degrees).
e. Check shaft tube circumference for scratches. Use magnifier.
(1) Longitudinal scratches deeper than 0.006 INCH, radial scratches deeper than 0.004 INCH, 45-degree
longitudinal/radial scratches deeper than 0.002 INCH, and scratches within 15 degrees of lengthwise axis
deeper than 0.005 INCH are not acceptable.
(2) The following criteria apply only to raised diameters (4.655/4.750 INCH) at extreme ends of tubes. All
scratches deeper than 0.015 INCH are not acceptable.
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