Use a rocket blower and remove all the small metal shavings and dust and use a paper towel and cotton swabs with naphtha to clean everything. This aperture ring will have some old grease on it. Most things that create a dust barrier to the lens I use a very small amount of Super Lube silicone grease. By small...I mean I work it in like you would work in hand lotion or shoe polish. You shouldnt be able to see gobs of grease anywhere, just a light coating.
Next we are going to remove the mid element. There is one set screw that retains the front/mid element housing in place. Its the silver one on the right...again mine was superglued in place.
Its tiny--dont lose it!
