German PTI bearings, PTI models, PTI prices

PTI bearings are roller bearings with cylindrical rollers. Relative to their diameter, the rollers are both thin and long. These rollers are called needle rollers. Despite having a small cross-section, the bearings still have high load-carrying capacity. Needle roller bearings are equipped with thin and long rollers (roller diameter D ≤ 5mm, L/D ≥ 2.5, where L is the roller length). Therefore, the radial structure is compact. When the inner diameter size and load capacity are the same as other types of bearings, the outer diameter is the smallest, making them particularly suitable for support structures with limited radial installation dimensions. Depending on the application, bearings without inner rings or needle roller and cage assemblies can be selected. In this case, the journal surface of the shaft and the housing bore surface matching the bearing serve directly as the inner and outer rolling surfaces of the bearing. To ensure that the load capacity and operating performance are the same as bearings with rings, the hardness, machining accuracy, and surface quality of the raceway surfaces on the shaft or housing bore should be similar to those of the bearing ring raceways. This type of bearing can only withstand radial loads.

PTI bearing selection

When selecting bearings, the main factors to consider are as follows: 1) Bearing load. The magnitude, direction, and nature of the load on the bearing are the main factors in bearing selection. When selecting a bearing based on load magnitude, compared to the point contact in ball bearings, the main components in roller bearings have line contact, making them easier to use for heavy loads, with less deformation after loading. When selecting a bearing based on load direction, thrust bearings are generally chosen for pure axial loads. Thrust roller bearings are selected for larger axial forces. Thrust ball bearings are selected for smaller axial forces. For pure radial loads, deep groove ball bearings, cylindrical roller bearings, or needle roller bearings are generally used. When bearing radial loads along with small axial loads, deep groove ball bearings or tapered roller bearings can be chosen; when axial loads are large, angular contact ball bearings with larger contact angles or tapered roller bearings can be used. [2) Bearing speed. Generally, speed does not significantly affect the choice of bearing type, but when the speed is high, speed must be included in the bearing selection criteria. Compared to roller bearings, ball bearings have higher limit speeds, so ball bearings are preferred in high-speed situations. With the same inner diameter, the smaller the outer diameter, the smaller the rolling elements, and thus the smaller the centrifugal force added by the rolling elements to the outer ring raceway, making them more suitable for high-speed operation. According to the properties given in Table 1, needle roller bearings are more suitable for high-speed operation. 3) Bearing self-aligning performance. When the centerline of the shaft does not coincide with the centerline of the bearing housing and there is an angular error, or when the shaft bends or tilts due to force, the axes of the inner and outer rings of the bearing will become misaligned. In this case, self-aligning bearings with certain self-aligning capabilities or mounted spherical ball bearings should be used. Roller bearings are most sensitive to bearing misalignment, and their load-carrying capacity in a misaligned state may be lower than that of ball bearings. Therefore, when the stiffness of the shaft and the support stiffness of the bearing housing bore are low, or when there is a large deflection moment, such bearings should be avoided. 4) Bearing installation and disassembly. When the bearing housing has no split plane and components must be installed and disassembled axially, bearings with separable inner and outer rings (such as N0000, NA0000, 30000, etc.) should be preferred.

PTI bearing lubrication methods

Lubrication is very important for bearings. The lubricant in bearings not only reduces friction resistance but also helps dissipate heat, reduce contact stress, absorb vibration, and prevent rust. Common lubrication methods for bearings include oil lubrication and grease lubrication. Solid lubricants are also used. The choice of lubrication method depends on the bearing speed. The dn value of the bearing (where d is the bearing inner diameter in mm; n is the bearing speed in r/min) is generally used to indicate the bearing speed. The figure shows the dn value limits for grease lubrication and oil lubrication.

PTI bearing installation methods

Before starting the assembly of rolling bearings, the rolling bearings need to be cleaned to keep them clean and tidy; then the rolling bearings are inspected and assembled according to their assembly requirements. 1) First, remove the residual grease and anti-rust oil from the rolling bearings. 2) Rinse the rolling bearings with kerosene first, then wash with gasoline, and dry with a clean cloth. 3) Other cleaning agents can also be used to clean the bearings, and the bearings should be wiped dry with a cloth. 4) Remember, do not use dirty oil, dirty cloth, or cotton yarn to clean or dry the bearings. Principles of rolling bearing assembly: Depending on the bearing structure, size, working conditions, and the fit nature of the bearing components, the pressure during assembly should be applied directly to the end face of the ring to be fitted, and it is not allowed to transmit pressure through the rolling elements. Rolling bearing assembly generally includes press-fit assembly, temperature difference assembly, and industrial frequency induction heaters. 1) Rolling bearings should not be removed from the machine parts if possible; if removal is necessary, correct tools and methods should be used. 2) Before assembling rolling bearings, appropriate cleaning agents and methods should be selected to clean them thoroughly based on the anti-rust method of the rolling bearings. 3) Before assembly, use internal and external micrometers to check the inner diameter of the bearing ring and the diameter of the shaft journal. The fit tolerance must meet the drawing requirements. 4) When rolling bearings are installed in split bearing housings, there should be no gap between the bearing cover and the mating surface of the bearing housing, but a certain gap should be left at the split joints on both sides of the bearing outer ring and the bearing housing. The side gap at the split joint can be measured and checked with a feeler gauge. If the gap is too small or "binding" occurs, a scraper can be used to scrape and increase the gap to comply with the table "Clearance between Rolling Bearings and Split Bearing Housings." 5) Rolling bearing assembly methods include driving-in, press-fitting, and hot mounting. For the driving-in method, a copper rod or sleeve should be used as a tool to transmit force during hammering, ensuring symmetrical force application on the bearing. The press-fit method uses a press instead of hammering, still using a sleeve to transmit force. During hot mounting, direct heating with flame is strictly prohibited. Use hot oil heated to 80~90℃. The oil temperature should not exceed 100℃. The bearing must not contact the bottom of the heating oil tank during heating; it should be suspended in the middle of the oil layer to avoid local overheating causing annealing. The heating time must not be less than 15min. After the inner ring expands to the required value, assemble it. Do not pause during the hot mounting process; quickly install the bearing to the correct position in one go. If the steel ball cage inside the bearing is made of oil-resistant plastic, water heating is preferred, but moisture should be wiped off promptly after assembly. 6) During rolling bearing assembly, the following requirements must be met: Inspect the cleaned bearings; they should be free of damage and rust, rotate flexibly without abnormal noise. Verify the fit category and dimensions of the bearing with the shaft journal and bearing housing. Proceed with assembly only after meeting requirements. During assembly, the pressure applied to the bearing should be evenly distributed and perpendicular to the end face, preventing unilateral force. Select the force application point based on the assembly relationship. For example, when assembling a bearing onto a shaft journal, pressure should be applied to the bearing inner ring. During assembly, the bearing and shaft shoulder should be tightly fitted. The gap between tapered roller bearings and radial thrust bearings and the shaft shoulder must not exceed 0.05mm, and for other assemblies, it must not exceed 0.1mm. The bearing cover and retaining rings must be flat and evenly tight against the bearing end face, and the clearance should be adjusted as specified in technical documents. During assembly, try to orient the end of the bearing marked with specifications outward for easy inspection and replacement. After assembly, manually rotate to check for jamming, then add an appropriate amount of grease. Sealing devices must be assembled according to regulations, and there should be no oil leakage after sealing. For single-row, double-row, and four-row tapered roller bearings and radial thrust bearings, axial clearance should be checked during assembly and adjusted according to bearing standards or technical documents. Various radial bearings, needle roller bearings, and spiral roller bearings must rotate flexibly after assembly. For bearings using grease, inject clean lubricating grease into 65%~80% of the cavity volume. For bearings lubricated with thin oil, do not inject grease. When assembling bearings, the axial clearance and axial preload (axial pre-interference) to be adjusted must comply with bearing standards or equipment technical document regulations.

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