How could it be possible?

major · 2013-06-03T18:05:34+0100

I used a cheap 49mm filter with the glass removed and screwed its rim to the lens of my DA 15mm to make an extension to fit a circular polariser as helpfully suggested by a forum member. It worked fine and was able to extend the hood as well as fitting the cap. Used it yesterday and found to my annoyance and frustration that I was unable to unscrew the glassless filter from my lens. It was not screwed on tightly! I could leave it on permanently but would rather not! Help, please!