Section 1001c(d) states: "Accurate measurement of flange height and flange thickness is not possible with the profile gauge. It is, therefore, recommended to use a wheel profile gauge with which accurate measurement... can be made." This implies the first "profile gauge" is a simple template to see if the flange is within a rough shape, while the "wheel profile gauge" is a calibrated instrument with a dial indicator or scale to give actual measurements.

The entire premise of an RD wheel is to replace the discs on a serviceable axle. Section 1003c's first step in the procedure for RD wheels is "Inspection of Axle journals... to confirm to be within the permissible limits." If the journals are undersize, the axle is no longer serviceable. The wheel set would effectively become an "RA" case, requiring a new axle as well. Since it started as RD, and the axle is bad, the only option is a new axle.

Section 1006b specifies: "Oil used in oil bath should be fortified with anti- oxidation, anti- foaming additives." When heated for long periods or to high temperatures, plain oil can oxidize (break down chemically) and foam, which is a safety hazard and can lead to uneven heating or coating the bearings with sludge.

Table 10.5 provides different limits for different makes: SKF has a limit of 0.33 mm, while FAG/NORMA has a stricter limit of 0.27 mm. This highlights the importance of knowing the bearing manufacturer.

The legend at the end of the UT section explains: "UT: Ultrasonic test 01: Code for Railway... 02: Code for type of work shop... 01: Code for place of workshop." In the example "UT.O 1.201," it is likely a concatenated code where "1" is the railway, "2" is the workshop type, and "01" is the place.

Section 1005e(v) states: "The collar should not be dismounted unless it is damaged or the interference fit with the axle is lost. Once dismounted, it should be invariably replaced." Collars are an interference-fit component. Dismounting them, especially if done improperly, will score or damage the mating surface, making a reliable re-fit impossible.

Section 1005e(vii) states: "The height should be 61 + / - 0.1 mm in the as cast condition and may be checked with the help of a gauge." This is before any machining or finishing.

Section 1004 and 1005a make it clear that the "direct mounted type" uses a bearing with a parallel bore (130 mm) that is a "shrunk fit" on the journal. There is no sleeve.

Section 1003a states this as a mandatory step: "If the wheels are sent for re-profiling without dismounting roller bearings from the journals, special protective covers should be fitted on the bearings... to avoid entry of chips / dust or damage to the bearing during machining." This is a critical preventative measure.

The UT appendix describes trace delay as: "In this technique, the specimen is tested part by part with normal probe." It's a methodical scanning approach, often using the initial pulse and the delay of the return echo to inspect specific sections of the axle individually.

Induction heating works by creating a strong magnetic field. Without a demagnetizing cycle, the bearing can retain residual magnetism. A magnetized bearing will attract metallic wear debris from the lubricant, which will then act as an abrasive and cause premature wear.

A thermal crack typically starts at the tread (braking surface) and propagates radially outward and inward. When it becomes visible on the outer, non-gauge face of the rim, it means the crack has traveled all the way through the width of the rim, severely compromising the structural integrity of the wheel, which can lead to catastrophic failure.

Section 1003b states: "Care should be taken to ensure that wheel disc number is preserved." This number is cast or stamped into the disc by its manufacturer. Preserving it allows the workshop to trace the disc back to its original heat treatment and casting records if a defect is ever found.

Section 1003b provides the exact proportion: "in the proportion of 1.2 kg. of white lead paste to 1 litre of boiled linseed oil." It's a specific weight-to-volume ratio.

The coefficient of thermal expansion for steel is constant. By heating only the bearing, its diameter increases significantly. The cold journal does not expand (or expands minimally from conducted heat during the brief mounting process). This creates a temporary clearance, allowing the bearing to slide on. When they equalize in temperature, the bearing contracts onto the journal, creating the interference fit.

Table 10.2 prescribes a surface finish value of 1.6 microns for the wheel seat. In engineering specifications, this is typically a maximum value (i.e., the surface must be at least this smooth, so the number represents the upper limit of roughness). A value of 1.8 microns is rougher than the limit and therefore not acceptable.

GO-NO GO gauges are functional gauges. The "GO" end checks that the thread is large enough (for a hole) or small enough (for a bolt) to assemble. The "NO GO" end checks that the thread hasn't worn beyond its maximum acceptable size (for a hole) or minimum acceptable size (for a bolt). It's a quick pass/fail test for thread integrity.

Section 1009b states: "Care should be taken not to keep a coach fitted with roller bearing stationary for a long time. Coaches grounded for a long time should be shunted up and down at regular intervals." This movement rotates the bearings slightly, allowing fresh lubricant to coat the rollers and preventing the vibration damage (false brinelling) mentioned in a previous question.

Section 1005e(viii) explicitly states: "Use cylindrical gauge fitted with dial indicator to check housing bore diameter at bearing seat (see figure10.10 & 10.11)." This is a precision method to check for both diameter and out-of-roundness.

In press-fit monitoring, a constant, steadily rising pressure curve is ideal. A sudden dip indicates a momentary loss of resistance, which typically happens when the surfaces "stick" and then break free, or when a burr or piece of debris is sheared off. This can create a scoring mark on the axle seat, compromising the fit.

The note at the end of section 1009a(iii) states: "All wheel sets withdrawn from service for any of the conditions mentioned above must be sent to the associated workshops for detailed investigations and further disposal." Understanding why a wheel shattered is crucial for preventing future failures.

This is a fundamental principle of mechanical maintenance. Fasteners, especially high-tensile ones, are designed to stretch slightly within their elastic limit to create clamping force. Over time and with repeated loading, they can exceed this limit, stretch plastically, or develop fatigue cracks, making them unreliable for reuse.

Section 1006b, for both labyrinth rings and bearings, mentions the wire mesh: "Oil bath should have a course wire mesh at bottom to allow sediments to settle below the part." This keeps the parts clean and prevents contaminants from sticking to the heated components.

Section 1009a(iii) point 3 states: "These are generally associated with small skid marks or 'chain sliding.'" Shelling occurs when the intense heat from a skid creates a brittle, thin layer of martensite on the tread, which then cracks and flakes off.

Section 1003a, in the box "On ICF axle journal," states: "A taper should not exceed 0.015 / 0.010 mm." This is a very tight tolerance to ensure the bearing seats evenly and maintains correct internal geometry when mounted.

False brinelling is a wear phenomenon characterized by depressions in the raceways at roller positions. It is caused by small-amplitude oscillatory motion or vibration while the bearing is not rotating, which prevents the formation of a full lubricant film, leading to fretting corrosion and wear. This is common in railway vehicles during transport or long-term storage.

Section 1.3 of the UT appendix states: "In such cases or in case where axle body is in forged condition it is advisable to use adequate quantity of grease as coupling media." The rough surface would otherwise trap air and prevent good sound transmission; high-viscosity grease fills these gaps better.

Section 1004 clearly distinguishes between the "Direct Mounted type" (cylindrical bore) used on new coaches and the "Sleeve Mounted type" (taper bore with withdrawal sleeve), which the manual states has "not been covered."

Section 1009a(ii) sets the limit for permissible flat surfaces on tread at 50 mm. A 45 mm flat is within this limit and is not an automatic cause for withdrawal, provided the rest of the inspection (e.g., for thermal cracks from the braking that caused the flat) is satisfactory.

The note signifies a move towards standardization. Instead of having a specific axle for 13t bogies and another for higher loads, a single, stronger axle (16.25t) is being used in all new wheel sets. This simplifies inventory, manufacturing, and maintenance.

Section 1005e(i) explicitly mentions this: "The practice of blocking of worn out holes and drilling a new hole 60° away from old ones reduces the probing area on axle face for ultrasonic testing." The end face is a critical scanning surface, and drilling new holes removes material and creates irregular surfaces that hinder effective UT.

Section 1005e(viii) states: "The axle box should be checked for distortion, particularly at the spring seat." It concludes with: "Housings not conforming to the limits or otherwise found unsatisfactory must be rejected." Distortion at the spring seat will affect the bogie's suspension geometry and load distribution.

Section 1006b, under "Mounting of Spherical Roller Bearing," is explicit: "There is no need to wash new bearings before installation." The rust preventive oil is compatible with the lubricants and cleaning it risks introducing contamination.

Table 10.5 gives the maximum permissible clearance for bearings in a dismounted condition. For FAG/NORMA, this limit is 0.270 mm. The measured value of 0.28 mm exceeds this limit, indicating excessive wear. Even though it's mounted, this high clearance is a rejectable defect as per the inspection criteria in section 1005d.

The radius is provided "to facilitate mounting." In press-fit engineering, a sharp corner (lack of radius) on the entry side of a hub acts as a stress raiser and can gouge the axle seat or cause the hub to crack as it's being forced onto the axle. The radius allows for a smoother, safer start to the pressing process.

Section 1003b explicitly states: "Surface finish of the axle on journals, wheel seat and middle portions should be checked with the help of a surface finish tester." Table 10.2 then prescribes a value of 1.6 microns for the wheel seat portion.

This is a trick question. While the diameter difference is 0.2 mm (which is within the 0.5 mm limit), the key issue is the absolute size. Table 10.1 states the minimum shop issue size is 836 mm. Both wheels are above 836 mm, so they are not condemned for size. The diameter difference is within the 0.5 mm limit, making it eligible for normal repair.

Section 3.3 of the UT appendix specifically warns about high-angle wedges: "The operator must ensure that the angle of refraction in steel not been affected by wear. Any change in the angle of wedges will seriously impair the test results." A worn wedge would change the beam angle, meaning the sound might not be directed correctly to detect flaws or return to the probe.

Table 10.6 lists the effect of a perished felt ring as: "1. Grease may ooze out from rear cover 2. Dust and water may enter the axle box." The entry of contaminants is the more critical failure mode as it directly leads to bearing damage and failure.

Section 1006b explains the rationale: "When tapping produces clear metallic sound, it shows that the part has seated correctly." If there were a gap between the ring and the shoulder, the sound would be dull or deadened. The metallic ring confirms solid metal-to-metal contact.

Section 1005e(vii) provides two critical figures: the as-cast height can be 61 ± 0.1 mm (range 60.9-61.1 mm), and the shoulder height must be 60 ± 0.1 mm (range 59.9-60.1 mm). Here, the shoulder height is 60.2 mm, which is outside its specified tolerance, rendering the cover unfit, regardless of the overall height.

Section 1006b states: "The stamp face of bearing should be kept towards outside so that stamping can be seen during inspection." This allows maintenance staff to verify the bearing's make, type, and date of manufacture without having to remove the axle box or any other components.

The entire process of an "RA" wheel assumes the discs are "serviceable." To confirm they are serviceable, they must first pass the inspection criteria. While measuring the bore is part of the process for matching, the first and most critical step is to ensure the disc itself is free from defects as per CMI-K003. A disc failing this would make the wheel set an "RD," not an "RA."

Section 1.1 of the UT appendix explicitly states that stamping displaces material into raised areas, resulting in inadequate acoustic coupling. This would prevent the ultrasonic energy from entering the specimen, hence no back wall echo.

Section 1005a specifies that bearings must be dismounted every alternate POH or 2 lakh km, whichever is earlier. The last dismount was 2.5 years ago (which likely equates to one POH cycle), and it has done 1.8 lakh km. Since the distance is close to the 2 lakh km limit, and the time cycle for dismounting (alternate POH) has been met, it requires dismounting.

Section 1006b warns that "Overheating (beyond 120°C or rapid heating may result in dimensional instability or change in material properties due to change in microstructure." Rapid heating creates high thermal stresses and uneven expansion, which can lead to microscopic cracks.

Ovality (out-of-roundness) is the difference between measurements on different axes at the same point. The difference here is 130.02 mm - 129.98 mm = 0.04 mm. Section 1003a specifies that ovality must not exceed 0.015/0.020 mm, so this is a rejectable defect.

Section 1003b states that variation must not exceed 0.05 mm. More importantly, it specifies that if a taper does exist, "the small diameter must be at an outside end of the hub bore (reverse taper is not allowed)." Here, the small diameter is at the outboard end, which is correct and permissible.

Section 1001c(i) specifies the wheel gauge must be 1600 mm (+2/-1 mm). The range is 1599 mm to 1602 mm. The measurement of 1602.5 mm is above the upper limit of 1602 mm, making the wheel set out-of-tolerance. The prescribed action for an incorrect wheel gauge is to press off and re-press the disc(s).