FarmerTed1971 wrote in post #16611804
Hogwash. All the aluminum is anodized anyways. There is no such thing as 'bond' in similar materials without a third component in the mix. It all comes down to thread tolerances and thicknesses of coatings. Temperature could also have an effect.
If you start your rotation backwards, as Frodge suggests, you will do it correctly every time and feel any resistance. If the threads are too loose (or tight) I suggest you try another filter.
Say Hogwash to the other photographers who have stated on the web that they have experienced that aluminum filters tend to stick together and are inherently more difficult to unscrew, yet have never experienced similar issues with brass ringed filters. Personally speaking, I can tell you that aluminum thread filters have become very difficult to unscrew from aluminum bodied OM lenses in spite of the fact that I had deliberately tried not to tighten them much.
On this thread http://www.pentaxforums.com …ilter-recommendation.html one person describes,
Join Date: Dec 2012
"I am a metalworker and galling does occur between filters and lens housings (and many other applications). Galling is when two assemblies of the same metal (aluminum, stainless, titanium) are fastened tightly together and develop oxide formation in areas of wear, sometimes resulting in a locked thread. At times it isn't just oxidation. It can be an actual transfer of metal between two assemblies.
" I have had several aluminum filter rings stuck onto the aluminum lens housing tight enough to require a filter wrench to pry them off. You might think that anodizing on these filters and lens housings are uniform but they aren't. In some spots the layer may be thin and as the filter is screwed on the anodizing may wear through. I have some filters where the bare aluminum shows through in multiple spots. It is in these areas that galling can occur. If you see a white residue left on the threads as you crank a stuck filter off then you know what that oxide formation looks like. If you don't think this is a common problem do a search for 'filter stuck on lens'."
The phenomenon is called 'galling', and you can read about it here