40mm TC Oil Seal – Metric R23 Double Lip NBR Rotary Shaft Seal, Multiple Sizes

Measure three dimensions: the shaft diameter (inner diameter), the bore diameter in the housing (outer diameter), and the housing depth (height/width). All three must match your application. This product has a fixed 40mm inner diameter — select the OD and height that match your housing from the variant options above. For reference: 40mm is approximately 1.575 inches, and 1 inch = 25.4mm.

TC refers to the double-lip (twin contact) design. The primary lip retains lubricant inside the housing, and the secondary lip generally acts as a dust and contaminant exclusion barrier. This is the most common configuration for rotary shaft seals used in gearboxes, pumps, axles, and general industrial machinery.

TC oil seals are designed for low-pressure dynamic sealing — typically up to 0.3 bar (approximately 4.4 psi) of differential pressure. They are not intended for high-pressure hydraulic circuits. For higher-pressure applications, a rotary union or dedicated hydraulic seal would generally be required.

NBR (nitrile rubber) offers good resistance to water, petroleum-based oils, and mild weather exposure, making it generally suitable for outdoor use in moderate climates. However, NBR is not recommended for prolonged UV exposure, ozone-rich environments, or contact with ketones, esters, or chlorinated solvents. For extreme outdoor or chemical environments, FKM (Viton) seals are typically a better choice.

These seals conform to the metric R23 / DIN 3760 standard for radial shaft seals. They are designed for metric shafts with a 40mm nominal diameter. For best sealing performance, the shaft surface finish should typically be Ra 0.2 to 0.8 micrometers (8 to 32 microinches). Always confirm your housing bore diameter and shaft diameter match the selected variant before installation.

Press the seal squarely into the housing bore using a seal driver or a flat plate — never hammer directly on the seal face or lip. Apply a thin film of clean grease or compatible oil to the sealing lip before installation to prevent dry-start damage. Ensure the garter spring (if present) is correctly seated. The primary sealing lip should face toward the lubricant being retained (inward).

NBR rubber typically performs reliably in a temperature range of approximately -40 degrees F to +250 degrees F (-40 degrees C to +120 degrees C). Continuous operation near the upper temperature limit may accelerate lip wear over time. For applications consistently above 250 degrees F, FKM (Viton) or PTFE-lipped seals are generally recommended.

Common signs of a failed rotary shaft seal include visible oil leakage around the shaft, oil staining on the housing exterior, contaminated bearings or lubricant, or a hardened and cracked seal lip visible on inspection. In most cases, seals should be replaced any time a gearbox, axle, or pump is disassembled for service, even if the seal appears intact.