Sling sewing machine

If the seal is being fitted to original equipment you may have some influence over the shaft and housing bore finish, but if you are replacing a worn seal you still need to take into account the condition of these 2 essential parts. 

Viton® 
High level of chemical resistance 
High temperature resistance

Spring The spring supplements the tightening force (i.e., the lip radial load) to ensure enhanced sealing performance and tight contact between the shaft and the sealing edge.The spring also prevents the deterioration of main lip sealing performance caused by high heat or other such factors.

Viton Oil Seals - A synthetic rubber and fluoropolymer elastomer, Viton is used to make oil seals that provide resistance in both high temperature, up to 250°C and low compression set components. They also offer a high resistance to chemicals and abrasions, so they can be used in elements that regularly interact with petroleum and solvents.

Metal

First, wash your hands before handling the oil seal. This is because dirt on the sealing surface or oil in fingerprints can compromise the integrity of the seal, while small particles can cause wear and tear, damaging the sealing surface and leading to leaks.
Secondly, do not unpack the seal unless you are ready to install it. After opening, the seal face must be cleaned before installing it on the equipment to prevent contamination.
Finally, ensure that your equipment is clean. This is because dirty equipment can affect the effectiveness of the oil seal.

Under the action of the skeleton oil seal, the rigidity of the oil film just makes the oil film and the air contact end form a crescent surface, which prevents the leakage of the working medium and realizes the sealing of the rotating shaft. The sealing ability of the oil seal depends on the thickness of the oil film on the sealing surface. If the thickness is too large, the oil seal will leak; if the thickness is too small, dry friction may occur, causing the oil seal and shaft to wear; if there is no oil film between the sealing lip and the shaft, it is easy to cause heat and wear. . Therefore, when installing, it is necessary to apply some oil on the sealing ring, and at the same time ensure that the skeleton oil seal is perpendicular to the axis line. If it is not perpendicular, the sealing lip of the oil seal will drain the lubricating oil from the shaft, which will also lead to excessive sealing of the lip. wear. During operation, the lubricant in the casing seeps out a little, so that it is ideal to form an oil film on the sealing surface.

Seals perform much better and longer when they are continuously lubricated with an oil that has the correct viscosity for the application and that is compatible with the seal lip elastomer material. The consideration of seal incompatibility, particularly with certain additives and some synthetic lubricants, should not be ignored, but unfortunately very often is.

Leather is probably the oldest of the lip materials still in common use, but the move towards mass production methods has seen a massive increase in the development of synthetic rubbers which lend themselves to accurate and repeatable injection and compression moulding. Nitrile (NBR) is still by far the most common elastomer for “normal” use, whilst Viton® (FKM/FPM) is rapidly replacing Polyacrylate (ACM) and Silicone (VMQ) for high-temperature applications. Viton® also has high resistance to abrasion and chemical attack making it a preferred elastomer. Recent developments in the use of PTFE for Rotary shaft seals has caused widespread interest particularly for high-speed shaft rotation or poor lubrication applications.

If this is not possible, you may be able to fit the lower retaining bolt into the upper mounting support, to hold the engine level. Or the gearbox may have to be jacked up and supported.