Technical Update
There is a well kept secret amongst oil seal engineers that goes something like this.
Mr A: The oil seal I bought from you is leaking worse than before.. this job is costing me buckets to redo and you are paying every cent of it!
Mr B: Talk me through how you installed it?
Mr A: Mindful that his every word is being assessed...
• I washed my hands
• I cleaned my bench and degreased the engine bay
• I wiped all my tools
• I inspected the housing and removed all burrs
• I inspected the shaft for wear grooves and there weren't any
• The shaft did look a bit dirty so I put it on the lathe and polished it with 400 grade emery paper
• I used the same oil as the engine to lubricate the seal before I pressed it in with a specially made drift.
On the surface the answer seems pretty good. The technician appears to have done all he could... or did he?
Oil seals are designed to operate without ever touching the shaft. Yes that is right - the lip seal is designed to never the shaft, but instead run on a super fine film of oil that seperates the lip from the shaft.
Shaft finish is critical in allowing the lip seal to operate without ever touching the shaft. The method by which this is achieved is called 'plunge grinding'.
Plunge grinding gives the shaft a peak and valley finish and removes the machine lead which acts as an auger or a pump.
When an ideal shaft is magnified under a microscope the finish resembles a mountain range - with lots of peaks and valleys. The peaks help maintain the oil under the lip - without which oil will seep like never before. When those peaks are removed (polished) there is nothing to help keep the oil under the shaft, which generates a lot of heat, premature wear and the seal leaks.
Try to avoid polishing the shaft - there is no need for it. If there is a groove worn on the shaft you could try repositioning the seal on a different position of the shaft - if that is not possible then a SKF Speedi Sleeves can be used with the confidence of knowing that they all have the correct shaft finish.
If you would like to know more please call our technical team, Massud Zhouand or Peng Chin on 9439 3910 for practical solutions.